Download Measles-Mumps-Rubella Vaccine and Autism In recent years there

Measles-Mumps-Rubella Vaccine and Autism
In recent years there has been public concern that there is a link between the MMR vaccine and autism. Review
by the American Academy of Pediatrics and the Institute of Medicine of published and unpublished research
has rejected the hypothesis, but fear of the vaccine continues. This concern is frequently voiced by parents to
their pediatricians.
The bottom line from both the AAP and the Institute of Medicine is clear: the MMR vaccine is NOT the cause
of autism; it cannot be implicated in the apparent increase in children with autism; and there is no scientific or
epidemiologic evidence to support administering these three antigens separately over time to prevent autism.
The etiology of autism remains a medical mystery. Genetic, environmental, infectious, metabolic and
immunologic factors have all been investigated with no clear, single answer. The “immune overload”
hypothesis has been applied broadly to childhood immunizations. It is a widely held belief, despite the fact that
scientific evidence does not support the immunologic basis of such a theory.
The current MMR-autism debate came to the forefront with the publication in the United Kingdom of a small
case series in 1998, in which 8 of 12 children with developmental regression were reported, either by the
parents or referring physicians, to have onset of developmental regression following the administration of MMR
vaccine in 8 of the 12 children. Concern was amplified by extensive media coverage.
Concerned that parent confidence in the MMR vaccine would be diminished, the U.K.’s Medical Research
Council and the Medicines Control Agency reviewed the existing data independently, and both concluded that
there was no evidence to support the hypothesis. Subsequent findings, obtained by studying 300 cases of
autism dating from 1979, are as follows : there was steady increase in the number of cases of children with
autism with no “step-up” when the MMR vaccine was introduced in 1988; vaccine uptake in children with
autism was no different from that in children without autism; there was no difference in age at diagnosis
regardless of vaccination status or timing of vaccination; and there was no evidence that regressive behavior
clustered in the time intervals following vaccination. Subsequent studies from Finland, the U.K. and the United
States demonstrated the same findings.
Despite what appears to be a clear increase in diagnosed cases of autism, this may reflect a broader concept of
autism, detection of cases with normal intelligence, changes in criteria, and increased detection due to better
available services. Special education programs require documentation of an appropriate diagnosis, so this may
contribute to the increasing number of children receiving this diagnosis. Conclusions about changes in the
incidence of autism over time are subject to such factors as population growth, migration flux and changes in
the birth rate making interpretations difficult. In addition, improved methods of detection may account for a
substantial proportion of the increase in diagnoses.
Measles immunization has practically eradicated the disease in the U.S. since the vaccine was introduced in
1963. Most cases of measles in this country have been traced to importation from other countries. Worldwide,
however, measles still accounts for approximately 1 million deaths per year, most in developing countries. It
also accounts for around 10% of mortality worldwide from all causes in children under 5 years of age.
Although measles is now an unusual childhood infection in most of the developed world, outbreaks do occur;
when it does occur, measles can be severe and can cause respiratory complication such as bronchopneumonia
and croup, can acutely infect the gastrointestinal tract leading to diarrhea, dehydration, malabsorption and
malnutrition; acute central nervous system complication include encephalitis.
(Condensed from “Measles-Mumps-Rubella Vaccine and Autism: The Rise (and Fall?) of a Hypothesis” Jason
L. Kastner, MD; and Bruce G. Gellin, MD, MPH ; Pediatric Annals 30:7)