Previous issues of
have addressed the safety of MMR vaccines, with strong evidence that there is no
link between MMR and autism or between MMR and inflammatory bowel disease. But
because concerns were so strong, it is valuable to return to the subject when even
more powerful evidence concerning connections between MMR and childhood illness
becomes available. Two more studies provide additional reassurance.
Measles vaccines and inflammatory bowel disease
This study  was conducted in the USA on the populations of four health
maintenance organisations as part of a vaccine safety programme coordinated by the
Centres for Disease Control and Prevention. In each of the HMOs trained medical
abstractors reviewed medical records using a standardised instrument. Cases were
individuals enrolled since birth (1958 was the earliest date) to 1989. Consistent
criteria were used for definite and probable diagnosis of Crohn's disease, ulcerative
colitis, or unspecified irritable bowel disease. This involved diagnosis by a
gastroenterologist, with signs and symptoms and a diagnostic test for irritable bowel
disease. Five controls were selected for each case, matched by sex, HMO and birth
year. Dates of vaccination, type of vaccine, and date of diagnosis were also
There were 155 cases of irritable bowel disease, with 152 definite or probable
cases. Seven cases had no discernible onset date, two were of unspecified disease,
and one was vaccinated when older than 10 years, leaving 142 cases and 432 controls
Most had been vaccinated. Figure 1 shows the percentages vaccinated with MMR, with a
measles-containing vaccine (MCV) or who were not vaccinated. The age at IBD diagnosis
ranged from under five years to over 25 years (Figure 2).
Figure 1: Type of vaccine used
Figure 2: Age at diagnosis of IBD
The risk of inflammatory bowel disease was the same for vaccinated or
unvaccinated people, split by type of vaccine or Crohn's disease or ulcerative
colitis. There was an average of about 140 months between vaccination and
diagnosis for cases and vaccination and control reference date for controls. Only
1% of cases developed inflammatory bowel disease within a year of vaccination and
only 1% of controls developed inflammatory bowel disease within a year of
Looking at whether children were vaccinated before 12 months, between 12 and 18
months, or after 18 months showed no difference in the risk of developing
inflammatory bowel disease.
Autism, MMR and GP visits
A UK study examined the rates of GP consultation before and after MMR
vaccination in children who became autistic and in controls . It used the
Doctor's Independent Network, a computerised database covering a million patients
in 127 practices providing lifelong medical histories for children remaining with
the practice from birth.
There were 79 cases with a diagnosis of autism, but one was immunised with MMR
after autism was diagnosed, and seven were never immunised. That left 71 cases
for analysis, with four controls chosen for each matched by age, sex, month of
immunisation and practice.
There was no difference in the number of visits in the two months (Figure 3) or
six months (Figure 4) before or after MMR vaccination for cases or controls.
Figure 3: GP visits and vaccination - 2 months
Figure 4: GP visits and vaccination - 6 months
These are two excellent studies. They were both conducted on defined
populations. They examined clinically important issues, either defined diagnosis
of inflammatory bowel disease, or visits to GPs that could reflect a change in
parental concern. In neither case was there any link with MMR vaccination.
One of the papers  has a superb discussion of methodological issues and
history of the linkage between concern over MMR safety and the evidence. Both
explain why the fears arose out of methodologically flawed studies.
Parents, and their physicians, can be reassured that high quality studies
conducted around the world continue to demonstrate that there is no link between
MMR and autism or inflammatory bowel disease. The weight of evidence on the
safety of MMR is now rather large. The evidence in support of a link is
A further thought is that there may just be the germ of an interesting paper or
thesis in all this, examining the chronology of the scare in relation to the
evidence available. There are lessons to be learned, certainly by news reporters,
certainly by editors of learned journals and their peer reviewers, and probably
by providers of healthcare. Disproving a negative is always going to be
difficult, but knowing that good efficacy and safety assessment measures are in
place for early warning is of major public importance.
- RL Davis et al. Measles-mumps-rubella and other measles-containing vaccines
do not increase the risk of inflammatory bowel disease. Arch Pediatr Adolesc
Med 2001 155: 354-359.
- S DeWilde et al. Do children who become autistic consult more often after
MMR vaccination? British Journal of General Practice 2001 51: 226-227.
- see also
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