| Vaccines are responsible for the control of many infectious diseases that were once
common in this country. However, the viruses and bacteria that cause vaccine-preventable
disease and death still exist and can be passed on to people who are not protected by
vaccines. Vaccine-preventable diseases have a costly impact, resulting in doctor visits,
hospitalizations, and premature deaths. Sick children can also cause parents to lose
time from work.
Polio
- Polio virus causes acute paralysis that can lead to permanent physical disability
and even death. Before polio vaccine was available, 13,000 to 20,000 cases of
paralytic polio were reported each year in the United States. These annual epidemics
of polio often left thousands of victims--mostly children--in braces, crutches,
wheelchairs, and iron lungs. The effects were life-long.
- Development of polio vaccines and implementation of polio immunization programs
have eliminated paralytic polio caused by wild polio viruses in the U.S. and the
entire Western hemisphere.
- In 1999, as a result of global immunization efforts to eradicate the disease,
there were about 2,883 documented cases of polio in the world. In 1994, wild polio
virus was imported to Canada from India, but high vaccination levels prevented it
from spreading in the population.
Measles
- Before measles immunization was available, nearly everyone in the U.S. got
measles. An average of 450 measles-associated deaths were reported each year between
1953 and 1963.
- In the U.S., up to 20 percent of persons with measles are hospitalized. Seventeen
percent of measles cases have had one or more complications, such as ear infections,
pneumonia, or diarrhea. Pneumonia is present in about six percent of cases and
accounts for most of the measles deaths. Although less common, some persons with
measles develop encephalitis (swelling of the lining of the brain), resulting in
brain damage.
- It is estimated that as many as one of every 1,000 persons with measles will die
in the U.S. In the developing world, the rate is much higher, with death occurring
in about one of every 100 persons with measles.
- Measles is one of the most infectious diseases in the world and is frequently
imported into the U.S. In 1997-2000, most cases were associated with international
visitors or U.S. residents who were exposed to the measles virus while traveling
abroad. More than 90 percent of people who are not immune will get measles if they
are exposed to the virus.
- According to the World Health Organization (WHO), nearly 900,000 measles-related
deaths occurred among persons in developing countries in 1999. In populations that
are not immune to measles, measles spreads rapidly. If vaccinations were stopped,
each year, 2.7 million measles deaths worldwide could be expected.
- In the U.S., widespread use of measles vaccine has led to a greater than 99
percent reduction in measles compared with the pre-vaccine era. If we stopped
immunization, measles would increase to pre-vaccine levels.
Haemophilus influenzae type b (Hib) Meningitis
- Before Hib vaccine became available, Hib was the most common cause of bacterial
meningitis in U.S. infants and children. Before the vaccine was developed, there
were approximately 20,000 invasive Hib cases annually. Approximately two thirds of
the 20,000 cases were meningitis, and one-third were other life-threatening invasive
Hib diseases, such as bacteria in the blood, pneumonia, or inflammation of the
epiglottis. About one of every 200 U.S. children under 5 years of age got an
invasive Hib disease. Hib meningitis killed 600 children each year, and left many
survivors with deafness, seizures, or mental retardation.
- Since introduction of conjugate Hib vaccine in December 1987, the incidence of Hib
has declined by 98 percent. From 1994-1998, fewer than 10 fatal cases of invasive
Hib disease were reported each year.
- This preventable disease was a common, devastating illness as recently as 1990;
now, most pediatricians just finishing training have never seen a case. If we were
to stop immunization, we would likely soon return to the pre-vaccine numbers of
invasive Hib disease cases and deaths.
Pertussis (Whooping Cough)
- Since the early 1980s, reported pertussis cases have been increasing, with peaks
every 3-4 years; however, the number of reported cases remains much lower than
levels seen in the pre-vaccine era. Compared with pertussis cases in other age
groups, infants who are 6 months old or younger with pertussis experience the
highest rate of hospitalization, pneumonia, seizures, encephalopathy (a degenerative
disease of the brain), and death. From 1990 to 1996, 57 persons died from pertussis;
49 of these were less than 6 months old.
- Before pertussis immunizations were available, nearly all children developed
whooping cough. In the U.S., prior to pertussis immunization, between 150,000 and
260,000 cases of pertussis were reported each year, with up to 9,000
pertussis-related deaths.
- Pertussis can be a severe illness, resulting in prolonged coughing spells that can
last for many weeks. These spells can make it difficult for a child to eat, drink,
and breathe. Because vomiting often occurs after a coughing spell, infants may lose
weight and become dehydrated. In infants, it can also cause pneumonia and lead to
brain damage, seizures, and mental retardation.
- The newer pertussis vaccine (acellular or DTaP) has been available in the United
States since 1991 and has been recommended for exclusive use since 1998. These
vaccines are effective and associated with fewer mild and moderate adverse reactions
when compared with the older (whole-cell DTP) vaccines.
- During the 1970s, widespread concerns about the safety of the older pertussis
vaccine led to a rapid fall in immunization levels in the United Kingdom. More than
100,000 cases and 36 deaths due to pertussis were reported during an epidemic in the
mid 1970s. In Japan, pertussis vaccination coverage fell from 80 percent in 1974 to
20 percent in 1979. An epidemic occurred in 1979 that resulted in more than 13,000
cases and 41 deaths.
- Pertussis cases occur throughout the world. If we stopped pertussis immunizations
in the U.S., we would experience a massive resurgence of pertussis disease. A very
recent study found that, in eight countries where immunization coverage was reduced,
incidence rates of pertussis surged from 10 to 100 times the rates in countries
where vaccination rates were sustained.
Rubella (German Measles)
- While rubella is usually mild in children and adults, up to 90 percent of infants
born to mothers infected with rubella during the first trimester of pregnancy will
develop congenital rubella syndrome (CRS), resulting in heart defects, cataracts,
mental retardation, and deafness.
- In 1964-1965, before rubella immunization was used routinely in the U.S., there
was an epidemic of rubella that resulted in an estimated 20,000 infants born with
CRS, as well as 2,100 neonatal deaths and 11,250 miscarriages. Of the 20,000 infants
born with CRS, 11,600 were deaf, 3,580 were blind, and 1,800 were mentally retarded.
- Due to the widespread use of rubella vaccine, only 6 CRS cases were provisionally
reported in the U.S. in 2000. Because many developing countries do not include
rubella in the childhood immunization schedule, many of these cases occurred in
foreign-born adults. Since 1996, greater than 50 percent of the reported rubella
cases have been among adults. Since 1999, there have been 40 pregnant women infected
with rubella.
- If we stopped rubella immunization, immunity to rubella would decline and rubella
would once again return, resulting in pregnant women becoming infected with rubella
and then giving birth to infants with CRS.
Varicella (Chickenpox)
- Chickenpox is always present in the community and is highly contagious. Prior to
the licensing of chicken pox vaccine in 1995, almost all persons in the U.S. had
suffered from chickenpox by adulthood. Chickenpox was responsible for an estimated 4
million cases each year, including 11,000 hospitalizations and 100 deaths.
- Chickenpox is usually mild, but may be severe in some infants, adolescents, and
adults. Some people who get chickenpox have also suffered from complications, such
as secondary bacterial infections, loss of fluids (dehydration), pneumonia, and
central nervous system involvement. In addition, only persons who have had
chickenpox in the past can get shingles, a painful inflammation of the nerves. There
are about 300,000 cases of shingles that occur each year when inactivated chickenpox
virus is activated in people who have had chickenpox in the past.
- Vaccine coverage among children 19-35 months was 67 percent in 2000.
Hepatitis B
- More than 2 billion persons worldwide have been infected with the hepatitis B
virus at some time in their lives. Of these, 350 million are life-long carriers of
the disease and can transmit the virus to others. One million of these people die
each year from liver disease and liver cancer.
- National studies have shown that about 12.5 million Americans have been infected
with hepatitis B virus at some point in their lifetime. One and one quarter million
Americans are estimated to have chronic (long-lasting) infection, of whom 20 percent
to 30 percent acquired their infection in childhood. Chronic hepatitis B virus
infection increases a person�s risk for chronic liver disease, cirrhosis, and
liver cancer. About 5,000 persons will die each year from hepatitis B-related liver
disease resulting in over $700 million medical and work loss costs.
- The number of new infections per year has declined from an average of 450,000 in
the 1980s to about 80,000 in 1999. The greatest decline has occurred among children
and adolescents due to routine hepatitis B vaccination.
- Infants and children who become infected with hepatitis B virus are at highest
risk of developing life-long infection, which often leads to death from liver
disease (cirrhosis) and liver cancer. Approximately 25 percent of children who
become infected with life-long hepatitis B virus would be expected to die of related
liver disease as adults.
- CDC estimates that one-third of the life-long hepatitis B virus infections in the
United States resulted from infections occurring in infants and young children.
About 16,000 - 20,000 hepatitis B virus infected women give birth each year in the
United States. It is estimated that 12,000 children born to hepatitis B virus
infected mothers were infected each year before implementation of infant
immunization programs. In addition, approximately 33,000 children (10 years of age
and younger) of mothers who are not infected with hepatitis B virus were infected
each year before routine recommendation of childhood hepatitis B vaccination.
Diphtheria
- Diphtheria is a serious disease caused by a bacteria. This germ produces a
poisonous substance or toxin, which frequently causes heart and nerve problems. The
death rate is 5 percent to 10 percent, with higher death rates (up to 20 percent) in
the very young and the elderly.
- In the 1920s, diphtheria was a major cause of illness and death for children in
the U.S. In 1921, a total of 206,000 cases and 15,520 deaths were reported. With
vaccine development in 1923, new cases of diphtheria began to fall in the U.S.,
until in 2000 when only one case was reported.
- Although diphtheria is rare in the U.S., it appears that the bacteria continues to
get passed among people. In 1996, 10 isolates of the bacteria were obtained from
persons in an American Indian community in South Dakota, none of whom had classic
diphtheria disease. There has been one death reported in 2000 from clinical
diphtheria caused by a related bacteria.
- There are high rates of susceptibility among adults. Screening tests conducted
since 1977 have shown that 41 percent to 84 percent of adults 60 and over lack
protective levels of circulating antitoxin against diphtheria.
- Although diphtheria is rare in the U.S., it is still a threat. Diphtheria is
common in other parts of the world and with the increase in international travel,
diphtheria and other infectious diseases are only a plane ride away. If we stopped
immunization, the U.S. might experience a situation similar to the Newly Independent
States of the former Soviet Union. With the breakdown of the public health services
in this region, diphtheria epidemics began in 1990, fueled primarily by persons who
were not properly vaccinated. From 1990-1999, more than 150,000 cases and 5,000
deaths were reported.
Tetanus (Lockjaw)
- Tetanus is a severe, often fatal disease. The bacteria that cause tetanus are
widely distributed in soil and street dust, are found in the waste of many animals,
and are very resistant to heat and germ-killing cleaners. From 1922-1926, there were
an estimated 1,314 cases of tetanus per year in the U.S. In the late 1940s, the
tetanus vaccine was introduced, and tetanus became a disease that was officially
counted and tracked by public health officials. In 2000, only 41 cases of tetanus
were reported in the U.S.
- People who get tetanus suffer from stiffness and spasms of the muscles. The larynx
(throat) can close causing breathing and eating difficulties, muscle spasms can
cause fractures (breaks) of the spine and long bones, and some people go into a coma
and die. Approximately 30 percent of reported cases end in death.
- Tetanus in the U.S. is primarily a disease of adults, but unvaccinated children
and infants of unvaccinated mothers are also at risk for tetanus and neonatal
tetanus, respectively. From 1995-1997, 33 percent of reported cases of tetanus
occurred among persons 60 years of age or older and 60 percent occurred in patients
greater than 40 years of age. The National Health Interview Survey found that in
1995, only 36 percent of adults 65 or older had received a tetanus vaccination
during the preceding 10 years.
- Worldwide, tetanus in newborn infants continues to be a huge problem. Every year,
tetanus kills 300,000 newborns and 30,000 birth mothers who were not properly
vaccinated. Even though the number of reported cases is low, an increased number of
tetanus cases in younger persons has been observed recently in the U.S. among
intravenous drug users, particularly heroin users.
- Tetanus is infectious, but not contagious, so unlike other vaccine-preventable
diseases, immunization by members of the community will not protect others from the
disease. Because tetanus bacteria are widespread in the environment, tetanus can
only be prevented by immunization. If vaccination against tetanus were stopped,
persons of all ages in the U.S. would be susceptible to this serious disease.
Mumps
- Before the mumps vaccine was introduced, mumps was a major cause of deafness in
children, occurring in approximately 1 in 20,000 reported cases. Mumps is usually a
mild viral disease.
- However, rare conditions such as swelling of the brain, nerves, and spinal cord
can lead to serious side effects, such as paralysis, seizures, and fluid in the
brain.
- Serious side effects of mumps are more common among adults than children. Swelling
of the testes is the most common side effect in males past the age of puberty,
occurring in up to 20 percent to 50 percent of men who contract mumps. An increase
in miscarriages has been found among women who develop mumps during the first
trimester of pregnancy.
- An estimated 212,000 cases of mumps occurred in the U.S. in 1964. After vaccine
licensure in 1967, reports of mumps decreased rapidly. In 1986 and 1987, there was a
resurgence of mumps with 12,848 cases reported in 1987. Since 1989, the incidence of
mumps has declined, with an estimated total of 327 cases in 2000. This recent
decrease is probably due to the fact that children have received a second dose of
mumps vaccine (part of the two-dose schedule for measles, mumps, rubella or MMR) and
the eventual development of immunity in those who did not gain protection after the
first mumps vaccination.
- If we were to stop vaccination against mumps, we could expect the number of cases
to climb back to pre-vaccine levels, since mumps is easily spread among unvaccinated
persons.
CDC, National Immunization Program: http://www.cdc.gov/nip
Last updated: August 2001
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