Vaccine
Safety > Issues of Interest > IBD
FAQs (frequently
asked questions)
about
Measles Vaccine and
Inflammatory
Bowel Disease (IBD)
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At a
glance: There is strong scientific evidence to show that measles
vaccine does not cause inflammatory bowel disease (IBD). CDC
recognizes there is considerable public interest in this issue, and
therefore supports additional research regarding this hypothesis. CDC
is committed to maintaining the safest, most effective vaccine supply
in history. |
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Frequently
Asked Questions |
- What is Inflammatory Bowel Disease (IBD)?
Inflammatory Bowel Disease, also known as IBD, is
a general medical term used to refer to chronic inflammatory diseases of the
intestine.
Two common inflammatory bowel diseases are ulcerative colitis and Crohn's
disease. These chronic illnesses can inflame the gastrointestinal tract causing
bloody diarrhea, abdominal pain, and weight loss. Ulcerative colitis can affect
the entire large intestine or the rectum. Crohn's disease mainly affects short
segments of both the small and large intestine. Although IBD can begin at any
age, it's usual onset is from age 15 to 30 years. IBD is a rare disease with
3-20 new cases recognized per 100,000 persons per year.
Top
- What causes inflammatory bowel disease?
The cause(s) of inflammatory bowel
disease is not known.
There are several unproven theories as to the cause(s) of IBD:
- IBD is known to "run in
families" suggesting a possible inherited, or genetic
cause.
- A possible environmental cause is
suggested because Crohn's disease most often occurs in people who
smoke, are residents of Northern European countries and live in urban
areas.
- Other researchers speculate that the
disease may be caused by an infection or virus.
- Still others believe that the
body's immune system is reacting to unidentified or unknown antigens.
This antigen would cause the immune system to respond inappropriately
against normal intestinal tissue, resulting in chronic inflammation.
Measles, mumps
or rubella virus infection is not known to
cause IBD. The virus that causes measles
disease infects the respiratory system and
then spreads to lymphatic tissue (an important
part of our immune system). During the acute
infection, lymph cells in the gastrointestinal
(GI) tract are infected but whether this
causes chronic inflammation is highly questionable.
One theory speculates that measles virus
may persist in the intestine in certain individuals
and later trigger a chronic inflammatory
infection, however this has not been proven.
Because MMR vaccine contains a very weak
live measles virus it has been suggested
that measles vaccine could cause an inflammatory
process in the intestine. This theory has
not been proven and is speculative. Two types
of scientific data - epidemiological and
pathological - can be studied to look at
a possible link between measles infection
and IBD. However, because conflicting results
have been obtained for both types of data
by different investigators, this link can
not be established.
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- What about studies
that suggest an association between measles vaccine and IBD?
The possibility of an association between measles
virus and chronic inflammatory bowel disease was discussed in a 1998
study by Wakefield and colleagues. The researchers believed they
discovered a new childhood illness that caused bowel disease and
psychiatric problems including behavioral disorders and autism. MMR
vaccine was suggested as a possible cause. The theory is that MMR
vaccine could lead to intestinal inflammation resulting in decreased
absorption by the intestinal tract of essential vitamins and nutrients
which in turn could lead to developmental disorders. An editorial
expressing concerns about the study was also published in the same issue
(Chen 1998). That all patients in the study had bowel disease is not
surprising since all were referred to a department of gastroenterology.
Some of the concerns expressed were that in this small study (12
patients) there is no report of detection of vaccine viruses in
intestinal or brain tissue for any of the patients. Multiple
laboratories using more sensitive and specific tests, have failed to
detect any findings to suggest this. In addition, the GI pathology
should have existed prior to the behavioral symptoms to support their
theory. The researchers reported the onset of GI symptoms was unknown in
5 patients and noted that GI problems occurred after the onset of
behavioral symptoms in another 5 patients.
Two Swedish studies have also suggested a
high risk of Crohn's Disease in those exposed to measles in utero.
However, these studies involved very small numbers of cases, 2 cases in
the first study and 4 in the second study, 2 of which were cases in the
first study (Ekbom et al 1994, Ekbom et al 1996).
In 1995, researchers (Thompson et al.)
suggested in a retrospective cohort study that MMR vaccine might be a risk
factor for Crohn's disease. However, the selection and recall biases and
the differences in data collection in this study were so substantial as to
cast doubt on the validity of the findings.
Another study has reported finding
measles virus proteins and RNA in the intestinal tissue of cases of
Crohn's disease using in situ hybridization and immunologic staining
(Wakefield 1993). However, the validity of this finding was later called
into question when it could not be reproduced by other researchers (see
question #4).
In 2002, researchers (Uhlmann et al.,
2002) found measles virus fragments in the intestines of children with
"new variant" IBD (children with both IBD and developmental
disorder). Scientists looked for the presence of measles virus in the
intestinal tissue of 91 children with new variant IBD and 70
"controls" (children without this type of IBD). The researchers
found measles virus fragments in 75 out of the 91 children with IBD, and
in only 5 of the 70 controls. While this provides evidence for an association
between the presence of measles virus and IBD in children with
developmental disorder, it does not mean that natural measles virus or the
measles component of the MMR vaccine causes IBD or developmental
disorder. A commentary published with the article asserts that the data
could just as easily be interpreted as indicating that the IBD or the
developmental disorder cause the persistence of measles in the intestines
(Morris & Aldulaimi, 2002). In addition, the researchers did not
compare the virus found in the intestines of patients with the virus used
in the vaccine; nor did they provide information regarding whether or not
the children in the study had been previously vaccinated with MMR or had
previously contracted measles disease. The limitations of this study are
further discussed in a letter
written by the Director of CDC’s National Immunization Program to
the UK’s Chief Medical Officer.
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- Is there scientific
evidence to show there is no association between measles vaccine and IBD?
There is strong scientific evidence (both
epidemiological and laboratory) to show there is no association between
measles vaccine and inflammatory bowel disease.
A population-based study conducted by the
CDC in collaboration with four large HMO's, part of the Vaccine Safety
Datalink Project, concluded that there was no evidence that vaccination
with MMR or other measles-containing vaccines, or the the age of
vaccination early in life, was associated with an increased risk for the
the development of IBD (Davis et al, 2001). Using a case-control design,
the study compared patients diagnosed with IBD and those without IBD, and
looked at the vaccination history of MMR vaccine and the timing of
vaccinations. Vaccination with MMR or other measles-containing vaccines,
or the timing of vaccination early in life, did not increase the risk for
IBD.
Researchers in the UK (Frombonne &
Chakrabarti, 2001) conducted a study to test the idea that a new form, or
"new variant," of Inflammatory Bowel Disease (IBD) exists which
is a combination of developmental regression and gastrointestinal symptoms
occurring shortly after MMR immunization. Information on 96 children (95
immunized with MMR) who were born between 1992 and 1995 and were diagnosed
with pervasive developmental disorder were compared with data from 2
groups of autistic patients (one group of 98 born before MMR was ever used
and one group of 68 who were likely to have received MMR vaccine). No
evidence was found to support a new syndrome of MMR-induced autism. For
instance, the researchers found that there were no differences between
vaccinated and unvaccinated groups with regard to when their parents first
became concerned about their child’s development. Similarly, the rate of
developmental regression reported in the vaccinated and unvaccinated
groups was not different; therefore, there was no suggestion that
developmental regression had increased in frequency since MMR was
introduced. Of the 96 children in the first group, no inflammatory bowel
disorder was reported.
Another group of researchers in the UK
(Taylor et al., 2002) also examined whether MMR vaccination is associated
with bowel problems and developmental regression in children with autism,
looking for evidence of a "new variant" form of IBD/autism. The
study included 278 cases of children with autism and 195 with atypical
autism (cases with many of the features of childhood autism but not quite
meeting the required criteria for that diagnosis, or with atypical
features such as onset of symptoms after the age of 3 years). The cases
included in this study were born between 1979 and 1998. The proportion of
children with developmental regression or bowel symptoms did not change
significantly from 1979 to 1988, a period which included the introduction
of MMR vaccination in the UK in 1988. No significant difference was found
in rates of bowel problems or regression in children who received the MMR
vaccine before their parents became concerned about their development,
compared with those who received it only after such concern and those who
had not received the MMR vaccine. The findings provide no support for an
MMR associated "new variant" form of autism and further evidence
against involvement of MMR vaccine in the initiation of autism.
Four other epidemiologic studies have
failed to confirm the possible association between measles virus and
inflammatory bowel disease. Nielsen et al. (1998) examined all possible
cases of measles in pregnant women admitted to a Copenhagen hospital from
1915-1966. None of the offspring of the 25 identified women had developed
Crohn's disease. In their case-control studies, Jones et al (1997) and
Feeney et al (1997) found no association between IBD and measles infection
or measles vaccine, respectively. In 1995, Hermon-Taylor compared the
incidence of Crohn's disease in England and Wales with measles infection,
including information after the introduction of measles vaccine. No
association was found.
In another study, researchers used the
same laboratory methodology as Wakefield et al. (1993), and could not
identify any measles virus in patients with IBD, although they did find
the presence of other viral and bacterial agents (Liu et al., 1995).
Several other research groups using more sensitive and specific tests (polymerase
chain reaction, PCR) have not found any evidence of measles virus RNA in
the gastrointestinal tissues of patients with Crohn's Disease or
ulcerative colitis (Haga 1996, Iizuka 1995, Afzal 1998).
Top
- What does CDC
recommend for measles-mumps-rubella (MMR) vaccine?
The CDC continues to recommend two doses of MMR vaccine
for all persons; for children, the first dose is recommended at 12-15
months of age and the second dose is recommended at 4-6 years of age.
MMR vaccine protects children against dangerous, even deadly, diseases.
For instance, one out of 30 children with measles gets pneumonia. For
every 1,000 children who get the disease, one or two will die from it.
Thanks to vaccines, we have few cases of measles in the U.S. today.
However, the disease is extremely contagious and each year dozens of
cases are imported from abroad into the U.S., threatening the health of
people who have not been vaccinated and those for whom the vaccine was
not effective.
Although the risk of Inflammatory Bowel
Disease (IBD) is higher for those who have relatives with IBD, there are
no data to suggest that measles vaccine will increase or decrease this
risk. Measles vaccine is recommended for children with a family history of
IBD unless there is another specific reason not to vaccinate (for example,
in persons who are very ill and are not able to fight infections).
Top
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