Closed captioning script for CDC Surveillance of Vaccine-Preventable Diseases
videotape
GOOD:
Welcome to Surveillance of Vaccine Preventable Diseases. We are
coming to you live from the Centers for Disease Control and Prevention in
Surveillance is a key element of public health. With most
vaccine preventable diseases at an all time low in the
We have two instructors for this part of today’s program. Dr.
Jane Seward is the Chief of the Viral Vaccine Preventable Diseases Branch in
the National Immunization Program. Dr. William Atkinson is a Medical
Epidemiologist in the Immunization Services Division of the National
Immunization Program.
Now let’s look at today’s objectives. After this session, we hope you will be able
to do these things and much more: identify
3 main levels of the national surveillance system for vaccine-preventable
diseases; Locate the case
definitions for nationally notifiable diseases; List the critical information to collect for each reported case of the
disease; and.Describe the concept of
surveillance indicators. Our
program will begin with a discussion of the basic principles of disease
surveillance and case investigation,
right after this pause.
ATKINSON:
Today’s first topic is an overview of surveillance. Many of the
principles of surveillance, case investigation, and reporting are common to
almost all the diseases we will discuss today. So this is a good place to
begin. First, let me mention that the most recent edition of the surveillance
manual is the third edition, published in 2002. In addition to being a good
reference, it is also the primary text for this course. We no longer print the
manual, but it can be downloaded from the National Immunization Program website.
We will put a link to it on our broadcast resources website. The chapters on
specific vaccine preventable diseases are arranged in alphabetical order,
starting with diphtheria, and continuing through varicella. If you have a copy
of the manual it should be easy for you to follow along with us.
As a result of effective immunization programs, diseases that
once were major causes of death and morbidity among children in this country
now occur so infrequently that many of us have never seen a case. Our challenge
now is to identify the factors that allow the remaining cases to occur. We also
want to extend our success with the elimination of measles, rubella, and polio
to other diseases that occur more commonly, like pertussis, hepatitis A, and
varicella.
We do case investigations to help us figure out if we need to
take public health action. If action is needed, exactly what do we need to do?
At the local level, we need surveillance information rapidly so we can start disease control activities. This might
mean providing antibiotic prophylaxis for contacts of pertussis cases, or
vaccinating susceptible persons when outbreaks occur.
For each vaccine preventable disease, there are specific
critical data that must be collected in order to plan and implement appropriate
public health action.
For each case, we need demographic and relevant clinical data, vaccination history, and
laboratory test results. This is the information needed to classify cases,
and it is critical in the evaluation of cases of vaccine-preventable diseases.
In addition to gathering information about the case, You need to
try to identify the people that the case may have passed the infection TO. And
you need to identify the person the case got the infection FROM. You need to
find out whether the case is linked to an outbreak, or is an isolated, sporadic
case. Just because no other cases have been reported, you cannot assume that no
other cases have occurred.
At the state level, we need surveillance data on vaccine
preventable diseases to evaluate the
effectiveness of disease control programs. When there is a case of a
vaccine-preventable disease in someone for whom there is a vaccination
recommendation, it should serve as a warning to public health officials. There
may be other susceptible individuals who should have been vaccinated, but were
not. Or there may have been waning immunity in a vaccinated individual. You
need to find out whether the person was
vaccinated, and if not, WHY not? Were there missed opportunities to vaccinate? Is there a more widespread problem? In addition to the evaluation of disease
control programs, states have other needs for surveillance data. Surveillance
data are also needed to formulate and
evaluate immunization policy. At the national level, we use surveillance
data to formulate national immunization
policy and to evaluate the
effectiveness of immunization programs. We also rely on surveillance data
to evaluate the effectiveness of the
vaccines themselves, and to document
the impact of national immunization efforts. This is especially important
with new vaccines, such the meningococcal conjugate vaccine, and tetanus,
diphtheria, and pertussis vaccine – or TDAP- for adolescents and adults. New
vaccine schedules also require careful surveillance and evaluation. An example
of this is the recent recommendation for influenza vaccination of 6 to 23 month
old children. What we need from our surveillance system depends on where we are
in our disease control program. What we need early in the program or when there
are large numbers of cases is quite different than what we need when the
program is very far along with few cases. Of course, we need to ensure adequate
surveillance for vaccine adverse events for any vaccine currently in use,
regardless of the stage of disease control. We will talk about this part of
surveillance later in the program. Before we have a vaccine for routine use,
the information we need is pretty simple. We need to have a baseline of reported disease. Complete reporting is not essential,
but we do need year to year consistency.
e need national data to represent the epidemiology of the disease prior to the
availability of a vaccine. But during this phase, aggregate reporting of case counts is usually sufficient. When a
new vaccine is recommended for routine use and disease remains common, our goal shifts to monitoring the impact of
the national vaccination efforts. At this point, aggregate reporting of case
counts is still sufficient. When we have extremely good disease control, as we
have now with Haemophilus influenzae type b, we need enhanced surveillance so we can document vaccine impact, evaluate effectiveness, and monitor progress
toward disease elimination. We can use this information to figure out why
the cases that remain continue to occur. With good disease control, we need
detailed information from individual
case investigations, including vaccination
status and laboratory confirmation.
We also need highly specific case
definitions, because we really want to make sure that the cases we are
counting are real cases of the disease. This is the phase when every case
counts. When disease incidence is very low and we are striving for elimination,
the completeness of reporting and the quality of individual case investigations
are very important. At this point, the organism may no longer even be
circulating, and we can use molecular typing methods to help document that, as
you will hear later in this program.
So in summary, surveillance activities must be designed to fit
the public health need. We need baseline data for newly vaccine- preventable
diseases. But we need detailed, individual case investigations when we have
achieved higher levels of disease control through vaccination programs.
GOOD:
Thanks, Bill. We will begin with varicella in just a moment.
SEWARD:
Varicella, or chickenpox, is a common, highly infectious disease.
It has been vaccine preventable since 1995. Before varicella vaccine was
licensed in the
The good news is that vaccination coverage among children is
rising steadily and fewer cases of chickenpox are being reported. As the number
of cases decreases, the need for more complete surveillance increases. Currently,
most of the detailed information about the change in varicella epidemiology,
including reduced disease incidence, comes from active surveillance sites. In
1995, the National Immunization Program and state and local health departments
initiated active surveillance for varicella in three areas of the country-
This overall reduction in varicella since the availability of
the vaccine is not unique to the active surveillance sites. Among the states
that have consistently reported cases through the national notifiable disease
surveillance system – NNDSS- there has also been a significant reduction in
cases compared to the pre-vaccine era.
The epidemiology of varicella has changed in the 10 years since
vaccine licensure. In recent years the number
of varicella cases has leveled off. Although vaccine effectiveness has been
in the expected range of 80 to 85%, outbreaks
have been reported in highly vaccinated school populations. This raises the
issue of whether a second dose of varicella vaccine is needed routinely for
children. As anticipated, the proportion
of cases among vaccinated persons is increasing and the median age of patients is shifting towards
adolescence. So it is now increasingly important to ensure that older
children, adolescents, and adults are vaccinated.
We expect a shift in age to older children, adolescents, and
adults with the implementation of a childhood vaccination program. It is
important to track incidence of disease by age as well as proportions. As
mentioned previously, varicella incidence among adolescence and adults is
declining. Bill?
ATKINSON:
In 2002, the Council of State and Territorial Epidemiologists,
or CSTE, recommended that varicella be included in the National Notifiable
Diseases Surveillance System. States were encouraged to conduct ongoing
varicella surveillance to monitor vaccine impact on morbidity. CSTE
specifically recommended that states establish individual case-based reporting
systems for varicella surveillance by 2005. However, other forms of
surveillance such as case-based reporting in sentinel sites were considered to
be reasonable interim steps toward statewide case reporting. As of November
2005, 19 states have implemented individual case reporting.
Material from vesicular or papular skin lesions, and scabs are a
readily available clinical specimen. Polymerase chain reaction, or PCR, a
direct antigen detection method, is the recommended test for confirmation of
varicella. Direct fluorescent antibody, or DFA, is another direct antigen
detection method. State public health laboratories now have the capacity to
diagnose varicella infection either by PCR or DFA assays. Jane?
SEWARD:
Case-based varicella surveillance will allow us to monitor the
impact of the varicella vaccination program on disease incidence, morbidity,
and mortality. Systematic national case-based varicella surveillance will allow
us to evaluate the effectiveness of our vaccination program and policies. It is
possible that in the future we will need to use the varicella vaccine
differently than we now use it. For example, a second dose of varicella vaccine
is being considered for routine immunization. Case-based reporting will also allow
for implementation of control measures for varicella outbreaks. Because
varicella vaccine coverage is high, disease incidence has been reduced, as
noted in areas from which we have surveillance data. As a result, public health
action is now warranted in response to varicella outbreaks. The investigation of
varicella outbreaks will help determine whether the outbreak is a result of
vaccine failure or failure to vaccinate. However, what is reasonable to do will
of course vary based on the circumstances of the outbreak and the resources
available for control. Regardless, persons with varicella, as well as
unvaccinated children, should be excluded from child care or school during
outbreaks. In June 2005, the ACIP updated its recommendation for the use of
varicella vaccine for outbreak control. ACIP recommended that persons who have
received 1 dose of varicella vaccine receive a second dose during a varicella
outbreak. Guidelines for the investigation and management of varicella
outbreaks are currently being developed at CDC, and have already been developed
by several states. One additional component of varicella surveillance is the
investigation of all varicella deaths. These deaths are a major component of
the remaining burden of disease. Varicella deaths became nationally notifiable
on January 1, 1999. There has been a significant
decline in varicella-related mortality since the prevaccine era. The greatest decline in mortality has occurred
in children 1 to 4 years of age, the group targeted for vaccination. Declines have also been seen in infants,
older children and adolescents, and adults 20 to 49 years of age as a
result of a combination of vaccination and herd immunity effects. From 1998
through 2002, 231 deaths among all age groups, with varicella listed as the
underlying cause, were reported to the
Varicella case-based reporting and death reporting will provide evidence
about programmatic changes that are needed, and will improve varicella control.
We cannot change policy or improve our program for vaccine delivery without
this information. Cynthia?
GOOD:
Thanks Jane. We will talk about measles after this pause.
ATKINSON:
The Healthy People 2010 Objectives for the
Sometimes cases are linked to known importations, but sometimes
it can be very difficult to identify the index case. When the index case cannot
be identified, even with extensive case investigation, we can often link cases
together by comparing the measles VIRUS from cases and demonstrating that they
are closely related. This is called
molecular epidemiology.
Identification of measles virus genotypes allows us
to link apparently sporadic cases to importations, even when the index case cannot
be found. Analysis of the virus is the only method that allows us to
differentiate between vaccine virus and wild-type virus if the suspected case
of measles was recently vaccinated. Of course, as long as measles continues to
occur anywhere in the world, we remain at risk in the
With vaccination coverage now at record high levels, many of the
people who remain susceptible are unvaccinated because of religious or
philosophical exemption. They are likely to have close contact with other
persons who share these beliefs. This sets up a situation where further spread
is very likely. An example of this was a measles outbreak with 34 cases in
The good news is that prompt recognition of the disease, with
appropriate control measures, can limit the spread of measles. So let’s move on
to some guidelines that will help you recognize and contain measles, should you
suspect it. You should suspect measles when you see or hear about a person with
an illness that includes a generalized
rash for 3 days or more, a temperature of 101 degrees Fahrenheit or greater,
which is 38 point 3 degrees centigrade, and either cough, or coryza, or conjunctivitis. Of note, some persons
with measles virus infection, especially those who have received measles
containing vaccine in the past, may have a milder disease with fewer symptoms.
These cases may not meet the clinical case definition and should be lab tested
in the context of an outbreak or if there is epidemiological linkage to a
confirmed case. Jane?
SEWARD:
Generally, a previously susceptible person exposed to either
vaccine or wild type measles virus will first develop an IgM response, followed
by an IgG response. The IgM response, shown here by the purple line, is usually detectable in the first 48 to 72 hours
after onset of rash, and peaks about 2 weeks later. So if the blood specimen is
drawn too early in the course of disease it may be falsely negative and should
be repeated after 72 hours of rash onset.
IgG antibody, shown by the yellow
line, is usually not detectable until later in the illness. IgG peaks later
than IgM, and remains detectable for many years, probably for the rest of the
person’s life. For confirmation of measles, IgG testing requires the
demonstration of a significant rise in measles antibody between the acute and
convalescent specimens, so two specimens are needed. The first serum specimen
should be drawn as soon as possible after rash onset, and at the latest within
7 days after rash onset. The second specimen should be drawn 10 to 30 days
after the first one.
Because tests for IgG require two serum specimens,
and because a confirmed diagnosis cannot be made until the second specimen is
obtained, IgM tests are preferred. However, a negative IgM- even when properly
drawn- does not rule out measles in a previously vaccinated person and acute
and convalescent IgG testing, or virologic testing will be necessary. The serologic test
most commonly performed for measles antibody is an enzyme linked immunoassay,
which is also known as an ELISA or EIA. CDC has developed a highly sensitive
and specific IgM test for measles and has trained personnel from every state
public health laboratory in its use. The CDC IgM test is the preferred
reference serologic test for measles. In addition, efforts should be made to obtain specimens for viral isolation from
all sporadic cases, or from at least some cases in each outbreak. These specimens should be obtained at the time of
the initial investigation, not later after serologic test results are
received. Viral isolates are essential
for tracking the epidemiology -the MOLECULAR epidemiology- of measles now
that we no longer have ongoing indigenous transmission in the
Once community awareness is increased during an outbreak, many
cases of febrile rash illness may be reported as suspected measles. The
magnitude of the outbreak will be exaggerated if these cases are classified as
confirmed in the absence of laboratory confirmation. This is particularly
important as the outbreak is ending. At that point, laboratory confirmation
should be sought on all suspected cases. During a case investigation, it is
important to obtain an accurate and
complete immunization history on all confirmed cases. Measles case
investigations should include complete immunization histories that document all
doses of measles- containing vaccine. Efforts should be made to identify the source of infection for every confirmed
case of measles. Case patients or their care givers should be asked about
contact with other known cases. When no history of contact with a known case
can be elicited, opportunities for exposure to unknown cases should be sought. Such
exposures may occur in schools,
following contact with international visitors, while visiting tourist locations, during air travel or, unfortunately, in
healthcare settings. Unless there is a history of exposure to a known
person with measles, patients or their care givers should be closely questioned
about other exposure settings. The next thing you should do is assess the potential for transmission, and
identify contacts. Transmission is particularly likely in households, schools
and other institutions, such as colleges, prisons, and in healthcare settings.
Contacts of the case patient during the infectious period should be identified.
For measles, the infectious period is from 4 days before to 4 days after onset
of the rash. In general, contacts that have not received two valid doses of
measles containing vaccine on or after the first birthday are considered
susceptible. These contacts may be at risk for infection. These contacts should
be vaccinated- ideally within 72 hours of exposure.
Now that measles is no longer an endemic disease in this
country, importation of measles cases from outside the
GOOD:
Thanks, Jane. We will be back in just a moment to talk about
rubella.
ATKINSON:
In this segment, we are going to discuss rubella. Like measles,
indigenous rubella and congenital rubella syndrome were targeted for
elimination in the
A worldwide rubella epidemic occurred in 1962 through 1965. An
estimated 12 point 5 million cases of rubella o
With rubella epidemics continuing to o
REEF:
Rubella
and congenital rubella syndrome, or CRS, were targeted for elimination in the
ATKINSON
Let’s talk now about rubella case investigation. A mild case of
measles may mimic rubella. Measles virus infection should always be ruled out
by laboratory testing if the diagnosis of rubella is being considered.
Likewise, rubella should always be considered in the evaluation of a febrile
rash illness. If serologic testing for measles is negative, testing for rubella
should always be done. A case of rubella may be laboratory confirmed by isolation of rubella virus; by
demonstrating a significant rise in
serum rubella IgG antibody level by any standard assay; or by the presence of serum rubella IgM antibody.
The laboratory criteria for confirmation of CRS are isolation of rubella virus from the infant; or detection of rubella virus by polymerase chain reaction - PCR- or
serologic confirmation. Many rash illnesses mimic rubella infection, and up
to half of rubella infections may be subclinical. So the only reliable evidence
of acute rubella infection is from the laboratory. Similar to measles a
negative IgM test does not rule out rubella in a vaccinated person. If the index
of suspicion is high, particularly if additional cases occur, obtain virologic
specimens as well.
Surveillance for rubella involves the serologic evaluation of
persons with febrile rash illness, and monitoring for the typical sequelae of
infection during pregnancy. Careful surveillance and continued high vaccination
coverage will help assure that congenital rubella syndrome remains a thing of
the past. Cynthia?
GOOD:
Bill, in the past Latin American has been the source of many
rubella cases imported into the
ATKINSON:
You
are correct that Latin America, particularly
GOOD:
Thanks, Bill. We will come right back to talk about mumps
surveillance.
SEWARD:
Mumps virus can cause illness with an acute onset of
unilateral or bilateral tender, self-limited swelling of the parotid or other
salivary gland, lasting more than 2 days, without other apparent cause. The
number of reported mumps cases in the
The combination measles, mumps, and rubella vaccine
has contributed to the same high coverage rate for mumps as we have already
discussed for measles and rubella. Although mumps is thought to be less
infectious than either measles or rubella, the reported disease rates are much
higher than for the other two diseases. In 2004, 258 mumps cases were reported in contrast to 37 cases of measles
and 10 cases of rubella. 32% of these
cases were among children 1 through 9 years of age. Vaccine history was known for only 87, or 34% of the cases. Of
those, 50, or 57% had received at least
one dose of mumps containing vaccine. Of the 258 cases reported in 2004,
only 95, or 37% were laboratory confirmed. It is very likely that many of the
cases lacking laboratory confirmation are actually not due to infection with
mumps virus. However, we cannot say with certainty because of our poor record
of laboratory testing.
Mumps vaccine is routinely used in only 56% of
countries or areas in the world. Importation of mumps into the
During 2004, a mumps outbreak with 31 cases occurred in a
Confirmed mumps cases are those that are laboratory
confirmed or that meet the clinical case definition and are epidemiologically
linked to a confirmed or probable case. Note that a laboratory confirmed case
does not need to meet the clinical case definition. Acute mumps can be
laboratory confirmed by isolation of
mumps virus in cell culture, detection of mumps virus by PCR, a significant rise in serum mumps IgG
antibody, or the presence of serum
mumps IgM antibody. Serologic testing is the simplest method of confirming
a case of mumps. Remember that as with measles and rubella, mumps IgM may be
transient or missing in individuals who have had any doses of mumps-containing
vaccine. Sera should be collected as soon as possible after symptom onset for
IgM testing or as the acute specimen for IgG seroconversion. Convalescent sera
should be drawn two weeks later.
The clinical samples that are acceptable for mumps
virus isolation are throat or nasopharyngeal swabs, urine, and fluid collected
from the buccal cavity. The buccal cavity is the space between the cheek and
teeth. The parotid duct drains in this space near the upper rear molars. Fluid
from this area may yield the best viral sample, particularly when the parotid
gland area just below the ear is massaged for 30 seconds prior to collection of
secretions. Virus may be isolated from the buccal mucosa or urine from 7 days
prior until 9 days after onset of parotitis. Collection of viral samples from
persons suspected of having mumps is strongly recommended. The molecular
characteristics of mumps viruses provides important information that will help
determine whether endemic transmission is still occurring in the
Because the number of cases of mumps reported each
year is low, a detailed investigation should be conducted for EVERY case. The clinical
diagnosis of mumps is unreliable, so all cases of mumps MUST be laboratory
confirmed. In addition to demographic
and clinical data it is important to obtain accurate and complete immunization history. Recent
outbreaks have included many cases who had already received at least one dose
of mumps-containing vaccine. The source
of infection should be identified for each confirmed case of mumps. If
there is no history of contact with a known case, opportunities for exposure to unknown cases should be identified,
so that investigative efforts can be directed to locations of possible
exposure. Finally, potential for further
transmission should be assessed, and contacts of the case-patient during
the infectious period should be identified. For mumps, the infectious period
usually begins 3 days before, but occasionally as early as 7 days before the
onset of parotitis, and lasts until 9 days after symptom onset. Mumps vaccine
should be given to all exposed susceptible persons. Although vaccine has not
been proven to prevent the occurrence of disease when administered after
exposure, it will provide protection for future exposures.
Measles and rubella were eliminated from the
GOOD:
Thanks, Jane. We will be back to discuss hepatitis A
surveillance right after this pause.
ATKINSON:
Hepatitis means inflammation of the liver. Many different
viruses, as well as many environmental toxins, chemicals, and drugs can cause
hepatitis. In this segment of the program we are going to limit our discussion
to hepatitis A, caused by infection with hepatitis A virus, or HAV. The
incidence of hepatitis A has declined since 1995, when the vaccine was
licensed. This decline was due at least in part to programs for routine
vaccination of children. In 2004, about 5 thousand 7 hundred cases of hepatitis
A were reported. This is an incidence rate [N1]of about 2 per 100
thousand population, the lowest incidence ever reported. The true number of
hepatitis A cases is actually much larger than the number officially reported
to CDC, for several reasons. [N2]First, the likelihood of having symptoms with
hepatitis A depends on age. Although most
adults with hepatitis A develop jaundice, the majority of young children either do not have typical symptoms or are
completely asymptomatic. Only people with symptoms of hepatitis A are
reportable to the health department. Second, not everyone with symptoms of hepatitis A goes to a doctor, gets tested
and gets reported. This is because symptoms can be very mild. Mathematical
models have been used to estimate the true number of HAV infections. It is
estimated that on average there were about 112 thousand symptomatic infections each
year during 1980 through 1999. This was more than 4 times the number of
reported cases. [N3]In 2004 when
approximately 57 hundred cases were reported, CDC estimated that there were
actually more than 20 thousand people with symptomatic hepatitis A. The
incidence of hepatitis A is currently lowest among children younger than 5
years of age. In the prevaccine era, the highest incidence rates occurred among
children, but currently rates of disease are similar among children,
adolescents, and adults. After decades of large differences in rates among
racial groups, currently incidence rates are similar across races. Despite
declines in recent years, rates of disease remain higher among Hispanic
children and adults, compared to non-Hispanics.
HAV is transmitted by the fecal
oral route, and is easily transmitted through close personal or sexual contact. HAV is also transmitted through contaminated food or water. Because the
virus is present in the blood during the acute infection, bloodborne transmission is also possible, but is rare. Unlike
hepatitis B, hepatitis A virus infection does not lead to chronic infection.
The incubation period for hepatitis A
averages about 28 days with a range of 15 to 50 days. The most common signs
and symptoms associated with acute hepatitis A include jaundice, fever, malaise, anorexia, and abdominal discomfort. The
illness can be severe and 10 to 20% of
reported cases require hospitalization.[N4] While rarely fatal
in younger persons, the case fatality
rate is approximately 1% among reported cases who are older than 50 years. [N5]Infected people
with either symptomatic or asymptomatic infection can transmit HAV to others.
Hepatitis A virus can be found in the blood and stool of an infected person,
especially in the 2 weeks before onset of illness. Virus is shed in the stool
of people without symptoms as well as those WITH symptoms. Young children
infected with hepatitis A virus play an especially important role in
transmission because they can transmit the virus, but often have no symptoms of
the infection. The most frequently reported risk factors for HAV infection are household or sexual contact with a person who has hepatitis A, and international travel. Other less
commonly reported risk factors include illegal
drug use, and being a man who has
sex with men; however, 45 to 50% of
persons with hepatitis A have no risk factor that can be identified.
Hepatitis A vaccines have been available since 1995. The two licensed vaccines
are available in pediatric and adult formulations and are administered in a two
dose series. The pediatric formulation of both vaccines are licensed for
children 12 months through 18 years of age. These vaccines are highly effective
in preventing disease when given before exposure. Protection lasts at least 12
years, and likely for 20 years or longer. Historically, the areas with the
highest rates of hepatitis A were in the Western and Southwestern regions of
the
WASLEY:
Hepatitis
A vaccines were first introduced in the
SEWARD:
Currently, national surveillance for hepatitis A is for
symptomatic disease only. Hepatitis A disease is reportable in all states.
Asymptomatic cases though should NOT be reported to CDC. The clinical case
definition for acute viral hepatitis is an acute
illness with a discrete onset of symptoms and either jaundice or elevated serum aminotransferase levels. But clinical
information is not sufficient to differentiate a case of acute hepatitis A from
hepatitis of some other type. To tell them apart we need some help from the laboratory. To confirm a case of acute hepatitis A, that case must meet the clinical criteria and MUST also be positive for IgM antibody to hepatitis A virus. IgM
antibody to hepatitis A virus is detectable in virtually all patients with
acute hepatitis A but generally disappears within 6 months of the onset of
symptoms. IgG is the other antibody produced in response to HAV infection. IgG
persists for the person’s lifetime and confers protection against subsequent
infection.
There is one situation when a clinically reported case lacking
serologic information can also be reported as a confirmed case of hepatitis A. That
is when a person with hepatitis A is epidemiologically linked to another person
with laboratory confirmed hepatitis A. By epidemiologic link, we mean household
or sexual contact with a person with confirmed hepatitis A during the 15 to 50
days before the onset of symptoms. To prevent
secondary cases, the two main priorities are to identify whether there are persons at risk of becoming infected by the
case and second, to determine, if possible, the source of infection for the index case. Identification of the
source is important because there may be other people who continue to be at risk
of infection from the same source. Prompt case investigation and follow up with
the case and contacts is important to prevent further spread of hepatitis A.
There is a viral hepatitis worksheet and report form in the surveillance manual
that can help guide your investigation. The critical data to be collected for a hepatitis A case investigation
includes demographic information
such as age and race; clinical data including
symptoms and the date of disease onset; pertinent laboratory data including serologic testing and liver enzyme levels;
risk factor information; and vaccination status of the case. During
your case investigation, you should also develop a list of any susceptible contacts who require postexposure
prophylaxis. Once you have identified contacts, post exposure prophylaxis
should be offered. This must be given as soon as possible and not more than 14
days after the last exposure. The recommended post exposure prophylaxis for
hepatitis A in susceptible contacts is a single intramuscular dose of immune
globulin, or IG, and hepatitis A vaccine, where appropriate. Postexposure
prophylaxis is recommended for the sexual
and household contacts of a person with hepatitis A. Prophylaxis should be
considered for other close personal
contacts as well. These might include persons who shared illegal drugs with
the case or had ongoing close household like exposures, such as a regular
babysitter. There are other circumstances in which IG prophylaxis might be
used. For example, attendees and
employees of a child care center where a hepatitis A case is identified, or
persons who consumed food handled by a
hepatitis A virus infected food handler, may benefit from IG. For these
types of exposures, the benefit of giving IG will vary, and must be assessed specifically
for each situation. In areas that currently have a routine hepatitis A
vaccination program, hepatitis A vaccine can be given along with IG to contacts
for whom vaccine is recommended. The vaccine and IG may be given
simultaneously, but not in the same syringe as the IG, of course, and not at
the same anatomic site.In addition to identifying the contacts of the case for
postexposure prophylaxis, it is also important to identify- if at all possible-
the SOURCE of exposure for the case. Sources of exposure could most likely
include sexual and household contact with another person with hepatitis A,
illegal drug use, international travel, or consumption of contaminated food.
It is important to determine the sexual history of the case,
including whether they have had multiple sex partners[N8] or are a man who
has sex with other men. For hepatitis A cases, it is important to ask about
these exposures during the 2 to 6 weeks before they became ill.
Coordination of surveillance and immunization activities can
focus appropriate interventions and reduce missed opportunities. In addition,
surveillance data- especially risk factor data- will be important to assess the
effectiveness of vaccination recommendations and to identify additional
populations that should be vaccinated. Strategies
to improve and enhance surveillance should include improved case reporting. Now that
hepatitis A vaccine is recommended for all areas of the country these
recommendations for enhancing surveillance apply to every state. Healthcare providers should be educated
about the importance of reporting all cases of acute hepatitis. Hospitals
and infection control practitioners should report all patients with the
ICD-10 diagnosis code of B 15, the code for acute hepatitis A. Surveillance is
an important tool in hepatitis A disease prevention. Information gained through
surveillance can help prevent spread of disease from cases, and can also help
define vaccination and other prevention strategies. Cynthia?
GOOD:
Thanks, Jane. We will be back to discuss hepatitis B
surveillance right after this.
ATKINSON:
In 2004, about 6 thousand 2 hundred cases
of acute hepatitis B were reported in the
Historically,
acute hepatitis B has been a disease of older adolescents and young adults 15
to 39 years old. However, as vaccination coverage has increased among
adolescents, rates of disease among older adolescents and young adults have
declined. Rates of acute hepatitis B are now highest among persons 25 through 44
years of age. Transmission of hepatitis
B virus, or HBV, requires percutaneous exposure to blood of a person acutely or
chronically infected with HBV. Common risk
factors for infection with hepatitis B virus include sex with multiple partners, injection drug use, and men who have sex
with men. Other risk factors include occupational
exposure to human blood or medical interventions such as surgery, blood
transfusions, or organ transplants. The incubation period for acute hepatitis B
averages 120 days with a range of 45 to 160 days. Infants, children younger than 10 years of age, and immunosuppressed
adults with newly acquired HBV infection are usually asymptomatic. 30 to 50% of older children and adults are
symptomatic. When present, clinical symptoms and signs might include nausea, vomiting, abdominal pain, and
jaundice. Fulminant hepatitis B occurs
with a case fatality rate of zero point 5 to 1%. In adults with normal
immune systems, most – 94 to 98% - recover completely from newly acquired HBV
infection. In infants, young children, and immunosuppressed persons, most newly
acquired HBV infections result in chronic infection. Infants are at greatest
risk with a 90% chance of developing chronic infection if infected at birth.
Although the consequences of acute hepatitis B can be severe, most
of the serious sequelae associated with this disease occur in persons in whom
chronic infection develops. Persons with chronic HBV infection are often initially
asymptomatic. However, chronic liver disease develops in two-thirds of these
persons, and approximately 15 to 25% will die prematurely from cirrhosis or
liver cancer.
Persons with chronic HBV infection are a major reservoir for
transmission of the virus. Any person testing positive for hepatitis B surface
antigen- or HBsAg- is potentially infectious.
Until
recently, national surveillance for hepatitis B included only acute symptomatic
disease, and perinatal hepatitis B. Chronic hepatitis B was added to the list
of nationally notifiable diseases in 2003, to monitor morbidity due to chronic
disease and to guide prevention programs. The case definition for acute hepatitis B includes having clinically compatible symptoms, jaundice or
an elevation in liver enzymes and laboratory confirmation. The case definition for chronic hepatitis B includes only laboratory confirmation because symptoms are not always present. The
preferred test for laboratory
confirmation of a case of acute
HBV infection is a positive test for IgM
antibody to the hepatitis B core antigen. IgM antibody to core antigen is a
good marker for acute hepatitis B because it is generally detectable for only
the first six months after infection. If this test is not available, a positive test for hepatitis B surface
antigen- with a negative test for acute hepatitis A virus infection, if
done-, is sufficient to confirm a diagnosis of acute hepatitis B. ANTIBODY to
hepatitis B surface antigen indicates immunity to hepatitis B virus. Chronic hepatitis B infections are also
confirmed by laboratory criteria. Cases will be hepatitis B surface antigen positive, total anti-hepatitis B core
antibody positive- if the test was done -, and hepatitis B core IgM antibody
negative. Chronic infection can also be confirmed by having two positive HBsAg tests at least 6 months
apart. Perinatal hepatitis B infection is a chronic infection which results
from transmission of the hepatitis B virus from an infected woman to her infant
before, during, or soon after birth. Perinatal
hepatitis B infection is defined as the presence of hepatitis B surface antigen in an infant 1 to 24 months
of age, born in the US or US territories
to a hepatitis B surface antigen positive woman. Since perinatal infections
are almost always asymptomatic, there are no clinical criteria for these cases.
Postexposure
prophylaxis with hepatitis B immune globulin and hepatitis B vaccine MUST be administered
to infants born to HBsAg-positive woman. These infants should be tested for
HBsAg three months after the third dose of vaccine. These cases should
be reported through the national notifiable diseases surveillance system. For
either acute or chronic hepatitis B, in addition to the appropriate demographic
and clinical data, there are two priorities
in conducting case investigations.
First, you should identify
whether there are contacts of the case at risk of becoming infected, and
second, you should determine, if
possible, the source of infection for the index case. Information to be
collected for a hepatitis case investigation should include demographic and clinical data, laboratory data including serologic testing
and liver enzyme levels, risk factor
information, and vaccination status.
Pregnancy status of any HBV infected
woman should be determined to make sure that action is taken to prevent
perinatal transmission to her infant. For acute hepatitis
B, the general recommendation for postexposure prophylaxis is to give hepatitis
B immune globulin, or HBIG, and to begin the hepatitis B vaccine series within
14 days of last exposure. Persons in need of postexposure prophylaxis include sexual contacts of the case and any infant younger than twelve months of age
for whom the case is a primary caregiver. Also persons who have had identifiable percutaneous or permucosal exposure
to the blood of the case should be given prophylaxis. Providing postexposure
prophylaxis to non-sexual household contacts of the case or others with no
clear exposure to blood of the case is not recommended. However, providing
hepatitis B VACCINE to nonsexual household contacts, especially children and
adolescents, is highly recommended.
Persons
with hepatitis B infection that remain chronically infected should be referred
for clinical follow-up. These persons should be monitored for the development
of chronic liver disease and should be evaluated for treatment. In addition,
they should be advised on ways to prevent transmission of the infection to
others.
In
addition to contact identification for postexposure prophylaxis, it is also
important to identify the source of infection for acute cases. There may be
other people who continue to be at risk of infection from the same source. To
identify the source of infection for
acute hepatitis B infections, ask about exposure
during the previous 6 weeks to 6 months to another person with acute or chronic
HBV infection, injection drug use, occupational exposure to human blood, medical
interventions such as dialysis, blood transfusions, organ transplants or use of blood products. It is also
important to determine the sexual
history of the case, including whether multiple sex partners or men who have
sex with men. Surveillance for hepatitis B is an important public health tool.
Identification and reporting of persons with HBV infection assists public health
professionals in reaching contacts of cases who are at risk of infection so
that vaccination and postexposure prophylaxis can be provided, if appropriate. Surveillance
also helps public health understand the risks for infection, to provide the
appropriate programmatic resources to reduce the rates of acute and chronic
infection in the
GOOD:
Welcome
back to Surveillance of Vaccine Preventable Diseases! We hope you have had time
to take a break and get ready for the second half of the program.
We have a new instructor for this part of today’s program. Dr. John
Moran is the Acting Chief of the Bacterial Vaccine Preventable Diseases Branch
in the National Immunization Program.
GOOD:
High vaccination coverage has led to all time record low levels of
many vaccine preventable diseases- but not pertussis. Pertussis remains endemic
in the
MORAN:
Thank you Cynthia. Pertussis,
or whooping cough, is caused by the bacterium Bordetella pertussis. Pertussis
is characterized by severe paroxysmal coughing sometimes followed by vomiting,
in older adolescents and adults and an inspiratory whoop in infants. Some
adults experience incontinence or rib fracture from forceful coughing.
Pertussis in very young infants can be severe but may not present with the
characteristic cough and whooping. Very young infants can start the illness
with apnea - stopped breathing, and bradycardia - slow heart rate. Infants have
high rates of complications including pneumonia and hospitalization.
During the last 5 years, about 20 deaths due to pertussis have
been reported each year in the United States; most are among infants less than
4 months of age, who are too young to have received 3 doses of pertussis
vaccine, and so are not yet fully protected. This graph shows the number of
reported cases of pertussis by year from 1940 through 2004. Notice the scale of
the vertical axis– 250,000 cases. Between 1940 and 1945, an average of 175
thousand cases and 2700 deaths from pertussis were reported each year. With the
widespread use of pertussis vaccine in the late 1940s, the number of reported
cases began to drop, although not as rapidly as with some other diseases. Periodic
peaks of illness continued every 3 or 4 years. Since 1980, the reported cases
of pertussis have been gradually rising, again with periodic peaks of
illness. Since 2001, the pattern has
changed, with increases in 2002, 2003, and 2004. More than 25 thousand cases
were reported in 2004, the highest number reported since 1959. Although we
usually think of pertussis as a disease of children, we are now recognizing
pertussis in older children, adolescents, and adults more frequently than in
the past. Outbreaks are being reported in middle schools and high schools. This
is probably due to both an increasing awareness of pertussis as a cause of
cough illness in this age group and the increasing availability of sensitive
diagnostic tests, such as DNA polymerase chain reaction – or PCR.
Although infants typically have the most severe cases of
pertussis, older children and adolescents can also have severe illness. Here is
a short video of an adolescent with pertussis.
[UNSCRIPTED VIDEO OF BOY COUGHING, WITH FRENCH VOICEOVER]
ATKINSON:
Protection induced by pertussis vaccines, or by the disease for
that matter, is NOT life long and begins to wane after about 5 years. There
have been outbreaks in high schools where almost all the students had received
4 or 5 doses of pertussis vaccine. In some adolescents the disease is less
severe because they were vaccinated in the past, but these cases can still be
infectious. Other adolescents have classic cases of pertussis, even though they
were previously vaccinated. Because protection does not last, even VACCINATED
children are susceptible to pertussis by early adolescence. In fact, the
proportion of cases reported occurring in persons 10 years of age and older
increased from 20% in 1990 to 67% in 2004. In contrast, outbreaks in elementary
school students are not common- probably because most children get a booster
dose of pertussis vaccine before they start kindergarten.
During May and June, 2005, the Food and Drug Administration
licensed two booster tetanus, diphtheria, and acellular pertussis – Tdap vaccines
– that is capitol T, small d– a– p- for adolescents in the
There are now 3 DIFFERENT diphtheria, tetanus and acellular
pertussis vaccines licensed for use in infants and children. One of these
vaccines also comes in a combination with inactivated polio and hepatitis B
vaccines. The acellular pertussis vaccines for infants and children also differ
from the two new versions of diphtheria, tetanus and acellular pertussis
vaccines licensed for use in adolescents and adults in 2005. The three
pediatric versions contain different
COMPONENTS of the pertussis organism, different
AMOUNTS of these components, and the components
are made by different PROCESSES. Adolescent
and adult versions of the vaccines have reduced quantities of many of the
components compared with the pediatric formulations. With so many different
vaccines, you can see the importance of getting complete vaccine history for
all cases of pertussis, both pediatric and adult. All of the acellular
pertussis vaccines are less likely to cause reactions than the whole-cell
vaccines were. The new vaccines for adolescents and adults have about the same
rates of reactions as the currently recommended tetanus and diphtheria toxoids
vaccines used for booster doses against tetanus.
We now have had more than 10 years of experience with acellular
pertussis vaccines among infants and children, and we know that with those
vaccines immunity wanes after a few years. That is why we see pertussis outbreaks
in high schools. The new Tdap vaccines for adolescents and adults were
developed and are now recommended to provide protection as the immunity from
the childhood series wanes. But how long does protection persist following
acellular pertussis vaccines? Does it matter? Yes it does matter. As with any
vaccine preventable disease, we must monitor disease due to waning immunity –
to identify possibly needed changes or additions to immunization schedules.
How often would booster doses need to be given? It is expected
that additional booster doses of Tdap will be required in the future for adults
although the vaccines are currently approved ONLY for a SINGLE dose. At this
time we are not certain how long protection will last from the booster doses in
adults. But that is important for us to know. Again, you can see that use of
new vaccines in new populations requires careful surveillance, to monitor
vaccine program impact. John?
MORAN:
Now let’s talk about the investigation of a suspected pertussis
case. The diagnosis of pertussis should
be suspected in a person who develops a cough illness that lasts more than 7
days, or if the person has fits, or paroxysms of coughing. Cough is the
hallmark of pertussis. But remember that in very young infants pertussis may
present as apnea, or stopping breathing. When the diagnosis of pertussis is
suspected, appropriate specimens should be obtained for laboratory testing. For
national reporting, there are two different methods by which cases can be
laboratory confirmed. These methods include isolation of Bordetella pertussis from a clinical specimen, or a positive polymerase chain reaction assay,
PCR. Let me repeat that: for laboratory confirmation of pertussis, we need
either isolation of Bordetella pertussis from a clinical specimen, or a
positive PCR test. Direct fluorescent
antibody testing, or DFA, has low sensitivity and variable specificity, and
should NOT be used for laboratory confirmation. Commercial serological
tests for pertussis infection are not standardized, and there is no absolute
association between antibody levels and immunity. Results of serologic testing
are not used for case confirmation for national reporting except in
In addition to being the gold standard for diagnosis of
pertussis, culture is important for another reason. Isolates are the only way
to evaluate for antimicrobial resistance, and are used for molecular typing. PCR can also be used for pertussis
laboratory confirmation. This test is now widely
available, and has been found in many places to be a rapid, sensitive, and specific method for diagnosing pertussis. Unfortunately
some PCR assays have not been completely
reliable. That is why it is very important that cultures continue to be performed, even if PCR tests are used. We
have heard about the importance of obtaining a nasopharyngeal swab for
pertussis culture and PCR, but many of you may not have ever OBTAINED a
nasopharyngeal swab. The quality of the specimen collection is critical to
obtaining a positive test.
Since good technique in obtaining a nasopharyngeal swab is such
an important part of pertussis surveillance, we would like to show you a brief
video on the proper technique for NP swabs. Have a look.
[UNSCRIPTED VIDEO OF MAN OBTAINING A SWAB FROM HIS NOSE]
MORAN:
That video was produced by Dr. Jim Nordin of Health Partners in
GOOD:
Thank you, John. We will be back in a moment to discuss
influenza.
ATKINSON:
Influenza viruses are responsible for respiratory illness in
people of all ages throughout the world. The usual symptoms of uncomplicated
influenza are fever, muscle aches, headache, sore throat, nasal congestion,
cough, and extreme tiredness. Some people can become very ill from influenza.
Influenza can exacerbate underlying chronic diseases, and lead to viral or
bacterial pneumonia. The risk for complications of influenza is highest in
persons 65 years of age and older and in those with chronic health conditions.
In most years, an average of about 36 thousand people in the
In the
Influenza viruses
can spread very rapidly, and have no respect for the borders of states or
countries. As a result, knowledge of influenza virus activity in other
countries is critical.
So, how do we do
influenza surveillance in the
State and local health departments play a vital role
in annual influenza surveillance in numerous ways. State and local health
departments oversee all influenza
surveillance components; enroll and
maintain contact with the influenza sentinel providers; and promote year round surveillance for all
relevant influenza surveillance components. They also report influenza associated pediatric deaths; determine and report the state’s overall weekly estimate of influenza
activity; perform laboratory testing
for influenza and report results to CDC; and submit a subset of influenza isolates to CDC for antigenic
characterization. During an influenza pandemic some surveillance
enhancements might be instituted to improve geographic and demographic coverage,
and increase the amount of detail captured by particular components of the
surveillance system. In particular, we know that it will be necessary to
enhance surveillance by testing more specimens during the early stages of the
pandemic, report data more frequently, and perhaps collect additional data.
State and local health departments will play a critical role in implementation
of these pandemic surveillance enhancements. Cynthia?
GOOD:
Bill, the
possibility of a new pandemic of influenza has been in the news a lot in the last
few months. What can states do to get ready for another pandemic?
ATKINSON:
Yes, there has been
a lot of news about avian and pandemic influenza lately. The increasing spread
of avian influenza is certainly a concern. Fortunately the Department of Health
and Human Services released their long-awaited pandemic influenza plan in
November 2005. This is a very useful document that can help states and
localities prepare for pandemic influenza. We will put a link to the HHS
pandemic plan on our broadcast resources webpage.
GOOD:
Thanks, Bill. We
will be back to discuss Haemophilus influenza surveillance right after this.
MORAN:
Among young
children, invasive disease due to Haemophilus influenzae type b has virtually
disappeared in the last few years. With widespread use of conjugate Haemophilus
influenzae type b vaccines, this disease has changed from the most common cause
of bacterial meningitis in infants, to a medical rarity. The bacterium
Haemophilus influenzae can be either encapsulated
or unencapsulated. The capsule is
composed of polysaccharide, of which there are six antigenically distinct types. The capsular types are designated by the letters a through f.
Nontypable, or unencapsulated strains may also cause invasive disease, but are
generally less virulent than encapsulated strains. Nontypable strains are rare
causes of serious infection among children but are a common cause of ear
infections in children and bronchitis in adults.
Before introduction
of effective vaccines, the type b encapsulated strain, or Hib for short,
accounted for more than 95% of invasive Haemophilus influenzae disease among
children. In the prevaccine era,
there were an estimated 20,000 cases of
invasive Hib disease annually among children less than 5 years of age in
the
Laboratory support
for Haemophilus influenzae serotyping should be readily available through your state
laboratory. For advice on serotyping capability within your state, contact your
state health department.
Other than getting
the isolate for serotyping, what else needs to be done for case investigation?
After you hear about a possible case, you need to review laboratory, hospital,
and other clinical records to obtain the critical information needed on every
case. This includes demographic and
relevant clinical data. Clinical
data needed includes the clinical
syndrome, dates of hospitalization, date of first positive culture, and outcome
of the illness. Results of laboratory testing are critical. The serotype of the isolate, body fluid source
of the isolate, and antibiotic susceptibility are all important. Vaccination status should be obtained
for every case. Since there are several types of Hib vaccines, this means the date, manufacturer, and lot number of
each Hib vaccine dose. This information tells us whether the case occurred as a
result of vaccine failure, or failure to vaccinate. Finally, we need
information on risk factors for Hib
disease. One of the most important of these is whether or not the child
attended childcare and whether the child was premature. If the child attended childcare,
control measures may be needed for other center attendees. How can surveillance
for Hib disease be improved? Hib is a laboratory- based diagnosis and virtually
all cases are hospitalized for the first few days of the illness. As a result,
reporting can be virtually complete if all clinical microbiology laboratories
and all hospitals report the cases that they see.
With so few cases
of Hib disease now occurring, how can we be sure that our surveillance is good
enough to detect the few cases that may still be out there? Remember, only type
b disease is preventable by vaccination. That means that disease that LOOKS like
Hib, but is caused by non- type b strains, is still occurring at the same rate
it always did. Although rates vary in different populations, data from active
surveillance suggest that non-b cases continue to occur at a rate of about 1 or
2 cases per 100 thousand children younger than 5 years of age, per year. If
cases of invasive Haemophilus influenzae disease are being serotyped and
reported among children, and these cases are NOT due to type b, surveillance is
probably good enough to detect type b cases.
If you are not
finding type b cases, but you ARE finding NON-type b cases, that is good
evidence that type b disease is probably not present in your community. This is
an example of a surveillance indicator. We will be talking more about
surveillance indicators later in the program.
Cynthia?
GOOD:
Thank you, John. We
will be back in a moment to discuss pneumococcal surveillance.
ATKINSON:
The heptavalent
pneumococcal conjugate vaccine– PCV7 - was licensed by the Food and Drug
Administration in February 2000. It was made a part of the recommended
childhood immunization schedule in October of that same year. However, because
of vaccine cost and some manufacturing shortages, national coverage rates are
not as high as for the other routinely recommended pediatric vaccines. National
Immunization Survey data for 2004 indicate that national coverage is about 73%,
with coverage in states and metropolitan areas ranging from 44% to higher than 90%.
As with other
vaccine preventable diseases, we need to establish surveillance to monitor the
impact of our vaccination program. Before we talk about what such a program
might look like, a little background on pneumococcal disease. Streptococcus
pneumoniae are gram- positive bacteria.
There are 90 known serotypes. As with other encapsulated organisms, the
polysaccharide capsule is an important virulence factor, and capsular type
specific antibody is protective. Although all serotypes may cause serious
disease, a relatively limited number of serotypes cause the majority of
invasive infections. Overall, the 10 most common serotypes are estimated to
account for about 60% of invasive disease worldwide. But the ranking and
serotype prevalence differs by age group and by geographic area.
Among children younger
than 5 years of age in the
VAN BENEDEN:
CDC’s Active Bacterial Core
Surveillance – or ABCs - is an active, laboratory and population- based
surveillance system for invasive disease due to 6 bacterial pathogens: groups A
and B streptococcus, Haemophilus
influenzae, Neisseria meningitidis,
Streptococcus pneumoniae, and
methicillin-resistant Staphylococcus
aureus, or MRSA. The principal objectives of ABCs are to accurately
measure the incidence of these 6 bacterial pathogens; to determine their
epidemiologic characteristics; to track trends over time; and to provide an
infrastructure for further public health research. ABCs is a core component of
the Emerging Infections Program Network-or EIP – and is conducted at 10 EIP-
sites across the
MORAN:
Data from ABCs have
been invaluable for documenting the burden of invasive pneumococcal disease
among children, and for identifying groups of children at increased risk of
disease. The ABCs data have also been valuable in documenting the impact of
pneumococcal vaccination of children. In fact, since implementation of PCV7
vaccination, the ABCs indicate that rates of invasive pneumococcal disease have
fallen very significantly. In 2004, the rate of invasive pneumococcal disease
in children younger than 2 years was 38 cases per 100 thousand population, down
from 191 cases per 100 thousand population before the vaccine was licensed.
But ABCs only
operates in 9 selected locations. We cannot rely on it to document the impact
of each state’s program for vaccination of children with pneumococcal conjugate
vaccine. To monitor the impact of state’s vaccination programs, each state must
evaluate the impact of invasive pneumococcal disease with time and within
populations. These national data, based on each state’s surveillance, should be
used to look at rates between groups... to see if state programs are
appropriately reaching individuals and groups recommended for vaccination.
Passive surveillance
does not yield the same type of data as the ABCs related to tracking vaccine
impact or projecting real numbers of cases. But each state’s data would allow
comparisons among states to see if funding differences or immunization program
differences are leading to differences in disease rates. This would help identify
inequalities that need to be addressed at the national level. Fortunately, we
have a good model for how to go about doing this from surveillance for
Haemophilus influenzae invasive disease. Invasive disease due to either of
these organisms is a laboratory- based diagnosis. Laboratories usually provide
very complete case reporting. With a requirement for reporting of laboratory-
confirmed cases, and infection control staff backing up that system by
reporting hospitalized cases, national reporting for invasive pneumococcal
disease can be virtually complete. In 1999 the Council of State and Territorial
Epidemiologists voted to make invasive pneumococcal disease among children younger
than 5 years of age nationally notifiable. That is not to say that invasive
disease in older age groups is not important. But our national immunization
program is directed at young children, so that is the focus of our efforts in
surveillance, at least for now. Currently, however, only 31 states and the
District of Columbia have requirements for reporting invasive pneumococcal
disease among children younger than 5 years of age. Once we identify a case of
invasive pneumococcal disease in a child less than five years old, what
information should we collect? We need the core information that should be
collected for every case of vaccine preventable disease, including demographic and clinical data, and risk factors for invasive disease. For
pneumococcal disease risk factors include underlying medical conditions such as
asplenia or HIV infection, and out-of-home childcare. And of course, we are interested
in vaccination history. Most cases
will be among unvaccinated or incompletely vaccinated children. But there will
be cases reported among vaccinated children. These vaccinated cases could
represent vaccine failure -disease caused by a serotype included in the
vaccine. They could also represent disease caused by a serotype NOT included in
the vaccine. Remember that prior to PCV7 implementation, about 20% of invasive
disease in children was caused by serotypes that are not in the vaccine. However,
currently about 80% of invasive disease is caused by nonvaccine serotypes. The
ABCs serotyping study that was set up to monitor possible vaccine failures has
been completed, and in March 2005, CDC and CSTE notified states that serotyping
was no longer available through CDC for this purpose.
To differentiate
vaccine failure in a vaccinated child from disease caused by a serotype not included
in the vaccine, the isolate would have to be serotyped. Unfortunately,
serotyping of pneumococcal isolates is a specialized laboratory procedure that
is currently not commonly performed except by facilities conducting research
studies. CDC laboratorians and epidemiologists, together with their colleagues,
are working to develop a cost-efficient, more routinely available testing
system for serotyping pneumococcal isolates. But what should we do right now? At
this time, the focus of state-based
surveillance should be to compare
state rates to rates elsewhere to see if they are within expected range, and
to compare among populations within the
state to make sure their vaccination programs are reaching all groups
adequately. If states’ rates are increased, the next step would be to determine
the cause. In the special situations of an outbreak or increased rates, the CDC
laboratory may be able to provide serotyping. It is possible that with vaccine-types
going out of circulation, there could be more outbreaks of nonvaccine type
disease. In this situation you should contact the Respiratory Diseases Branch
of the
GOOD:
Thanks, John. We
will be right back to discuss meningococcal disease surveillance.
With the dramatic
reductions in Streptococcus pneumoniae and Haemophilus influenzae, Neisseria
meningitidis has become a leading cause of bacterial meningitis in the
This graph, from the ABCs active
surveillance system, shows rates of all reported meningococcal disease- not
just vaccine serotypes- by age group. The overall rate in the
As with Haemophilus
influenzae and Streptococcus pneumoniae, diagnosis of invasive disease due to
Neisseria meningitidis is based on isolation of the organism from a normally
sterile site. A diagnosis based on culture is quite specific, with infrequent
false positives. With the national requirement for reporting, laboratory
confirmation, and hospital staff reporting cases, reporting can be virtually
complete. Information that should be collected for a case of invasive Neisseria
meningitidis is similar to other diseases we have discussed today. We need the
core data, including demographic,
clinical, and risk factors. We need to know the person’s age and risk
factors because the current vaccine is only recommended routinely for certain age
groups, and for persons with specific risk factors. Vaccination history is important, and laboratory data provides critical information. To determine whether
a case could have been prevented by vaccination, testing must be performed to
determine the serogroup of the isolate. Serogroup testing of Neisseria
meningitidis isolates is performed by hospital and state public health
laboratories. Cases of serogroup A, C, Y, or W-135 in persons eligible for
vaccination may represent either a vaccine failure or a failure to vaccinate.
Cases that are type B are not vaccine preventable. With the licensure of
meningococcal conjugate vaccine, and the new recommendations for its routine
use among adolescents, a new era has begun in the prevention of this terrible
disease. Surveillance will play an important role as we monitor meningococcal
immunization programs and assess progress toward our prevention goals. Cynthia?
GOOD:
Thanks Bill. We
will be right back to discuss the surveillance of vaccine adverse events.
MORAN:
During this program
we have talked about the surveillance of vaccine preventable diseases- why it
is important, and how surveillance differs based on the level of control we
have achieved. But in our business, surveillance for DISEASE is only part of
the story. We also need to perform surveillance for the vaccines themselves-
for vaccine coverage, effectiveness and safety. We focus this section of the
program on the surveillance of adverse events following vaccination. We need to ensure adequate surveillance for
vaccine adverse events for any vaccine currently in use, regardless of the
stage of disease control. But surveillance for adverse events following
vaccination is especially important for newly licensed vaccines. We usually
give vaccines to healthy people- including very young children- and vaccines
often are required by state immunization laws. So vaccines are held to a higher
standard of safety than other medications. But like any medication, no vaccine
is perfectly safe or effective. Some vaccines cause minor adverse events like
local reactions or fever. And, rarely, they can cause serious adverse events,
like seizures, encephalopathy, or severe allergic reactions. But, until vaccine
preventable diseases are eradicated, we will continue to use vaccines. So it is
critical that all of us do everything we can to ensure that vaccines are as
safe as possible and to maintain public confidence in vaccines. To do this, we
need to monitor closely the occurrence of adverse events, evaluate possible
associations, and respond appropriately to those risks. Before licensure,
vaccines undergo extensive testing and
review for safety, immunogenicity, and efficacy. Prelicensure studies usually include unvaccinated comparison- or
control- groups, so we can determine which reactions were actually caused
by the vaccine. However, prelicensure trials include a relatively small number of participants. Usually, the vaccine has
been given to only a few thousand people, and usually they are monitored for a
limited time period. And the studies are often conducted in homogenous populations, meaning groups that
are less diverse than those in which the vaccine is ultimately used. And
finally, because the number of participants is relatively small the sensitivity for detection of uncommon or
rare adverse events before licensure is low. Because of the inherent
limitations of prelicensure testing, we cannot rely on prelicensure studies to
identify all the reactions that may occur once a vaccine is more widely used.
For that, we rely on postlicensure surveillance, which is the continuous
monitoring of vaccine safety in the general population after licensure. The National Childhood Vaccine Injury Act
was passed in 1986. This law required
that healthcare providers who administer vaccines and vaccine manufacturers
report certain serious adverse events following specific vaccinations. The
Act stipulates that the vaccines, the
adverse events, and the time of occurrence of the adverse event after
vaccination be reported. It also requires that any event listed in the
manufacturer’s package insert as a contraindication to subsequent doses of the
vaccine be reported. The Vaccine Adverse Event Reporting System, or VAERS, is a
national passive surveillance system that was established to provide a single
system for the collection and analysis of reports of adverse events following
vaccination. CDC and the FDA work
together on the system. The VAERS form, shown here, is included in the surveillance
manual. It can also be downloaded from the VAERS website. Healthcare providers
can complete and submit paper report forms, or may choose to submit a web-based
report. Additional report forms, assistance in completing the form, or answers
to other questions about VAERS are available 24 hours a day by dialing the
toll-free number 800-822-7967. You
can also Email VAERS at inf@vaers.org.
The objectives of
VAERS are to detect previously
unrecognized reactions to vaccines, to
detect increases or decreases in previously reported events, to detect pre-existing conditions that may
predispose to adverse events, and to
detect vaccine lots with unusual numbers and types of reported reactions.
The Food and Drug Administration reviews reports of death and other serious
events each week and conducts analyses of reports by vaccine lots. CDC conducts
additional analyses as needed to address specific vaccine or adverse event
concerns, and to evaluate trends in reporting. VAERS has limitations. It only
contains reports of people who experienced specific health events following a dose
of vaccine. The system does not contain information on ALL people who were
vaccinated, so it cannot be used to
estimate the rates of adverse events. It also cannot be used to determine whether the event was actually caused by
the vaccine. Analysis of VAERS data is intended to identify patterns of
adverse events that occur following the vaccine. However, population based
databases, such as the Vaccine Safety Datalink – or V-S-D, must also be used to
evaluate whether these events are causally associated with vaccine, or occurred
coincidentally. The VSD is a collaborative project involving CDC and several
large managed-care organizations and contains medical and immunization
information on more than seven million people. The postlicensure vaccine safety
monitoring system in the
GOOD:
Thanks, John. We
will be back in a moment to discuss surveillance indicators.
ATKINSON:
We rely on
surveillance to monitor the effectiveness of our immunization programs. But how
can we monitor the effectiveness or quality of our surveillance? We have
already talked about the difficulties of doing surveillance when the disease
for which we are doing surveillance is rare. How do we know if there were no
cases because there really WERE no cases, or because no one was looking? We
rely on surveillance indicators to monitor the quality of national
surveillance. We have already talked about the critical elements that need to
be collected during investigation of cases of vaccine preventable diseases.
These include demographic information, relevant clinical and laboratory data,
and vaccination status. Monitoring whether or not these data are reported lets
us track the quality of case investigation, and we do this routinely. But that
does not tell us whether or not zero cases reported REALLY means zero disease
or infection. This year in the
KROGER
Surveillance is a
critical component of public health.
ROUSH
National
surveillance for vaccine-preventable diseases traditionally relies on passive
reporting, which is often incomplete. In spite of this limitation, national
surveillance data are useful for routine surveillance because they are used
primarily for monitoring trends in disease occurrence rather than in response
to individual cases. However, for diseases with very few remaining cases, as
with most of the vaccine preventable diseases, surveillance data must be very
complete. Every case counts. We need to know whether zero reported cases means
that there is really no disease. Surveillance indicators have been developed to
assess the quality of national surveillance - that is, the ability of our surveillance
system to identify all cases, if and when they are present. In addition,
surveillance must be specific enough to exclude non-cases by adequate case
investigation and laboratory testing.
KROGER
How long have we
been using surveillance indicators for vaccine preventable diseases?
ROUSH
Methods to monitor
surveillance quality were first developed in 1988 by the Pan American Health
Organization as part of the polio eradication effort in the
KROGER
Indigenous
transmission of measles and rubella has been eliminated in the
ROUSH
Yes, we do.
Surveillance indicators for measles and rubella are quite similar. Both include
completeness of data, timeliness of reporting, proportion of cases that are
laboratory confirmed, and the proportion of chains of transmission that have an
imported source. If our surveillance system can identify imported cases of
measles and rubella, we have confidence that the system could identify
indigenous cases, too, if they were present. For rubella, we also measure the
proportion of cases among women of child-bearing age with known pregnancy
status. For measles, we measure the proportion of chains of transmission for
which a clinical specimen is submitted for virus isolation.
KROGER
That makes sense.
Is there a measles surveillance indicator related to cases that were ruled out
through case investigation?
ROUSH
Yes. Discarded
measles-like illness – or MLI - surveillance was established in 1997 to
document the ability of the
KROGER
Are there
surveillance indicators for any other vaccine preventable diseases?
ROUSH
Yes. We have also
developed indicators for Haemophilus influenzae and pertussis surveillance. For
Haemophilus influenzae, we measure the timeliness and completeness of case
information for children younger than 5 years of age, including vaccination history
and serotype. We can also track the incidence of non-type b disease among
children younger than 5 years of age. Based on active surveillance data, we
expect 1 or 2 cases of NON-type b Haemophilus influenzae per 100 thousand
children per year. So, if no cases of NON-type b disease are being found,
surveillance for type b disease may be inadequate. For pertussis, we measure
completeness of data for vaccination history and duration of cough, as well as
the proportion of cases that are laboratory confirmed or epidemiologically
linked to another confirmed case. We are working with federal and state
partners to develop surveillance indicators for other vaccine preventable
diseases as well, including mumps, varicella, and meningococcal disease.
KROGER
ROUSH
My pleasure.
ATKINSON:
These are a few
approaches to monitoring the quality of surveillance. We do surveillance to monitor the quality of
our immunization program. We use surveillance INDICATORS to monitor the quality
of our surveillance. With the incidence of many of the vaccine preventable
diseases at all time record lows, we CANNOT be sure that zero means zero unless
we can document that someone is looking.
GOOD:
This brings us to
the close of this edition of Surveillance of Vaccine Preventable Diseases.
Before we say goodbye, a comment about any unanswered questions you may have. If
you have any questions about disease surveillance procedures, case
investigation, or the availability of laboratory support, you should FIRST
contact your state immunization program. They will be able to answer most of
your surveillance questions. You can use the Internet to Email questions,
comments, or requests to the National Immunization Program. Our Email address
is nipinfo@cdc.gov. Throughout this
program we have mentioned several immunization resources, including the
Surveillance Manual. You will find links to these and much more on the National
Immunization Program website at www.cdc.gov/nip. Click on the Healthcare
Professional tab, and go to the Education and Training section. There you will
find a link to Broadcast Updates and Resources. Finally, if you would like to
find out more about upcoming Public Health Training Network courses, visit the
PHTN website at www.cdc.gov/phtn. Thank you for joining us today. It has been
our pleasure to bring this program to you. Goodbye
###
[N1]?1.9
[N2]Where did this “half with symptoms” come from? I don’t know how it could be true -% with symptoms completely dependent on age distribution.
[N3]I’ve left this at symptomatic cases, but of course the number for total infections is much higher.
[N4]The proportion is quite a bit higher, especially these days – do you want to use the% in the current surveillance report, at least as the upper end of a range?
[N5]What is the source for this?
[N6]What map are you planning to show here?
[N7]We should have another map here that shows this.
[N8]We ask about multiple sex partners???