What Parents Should Know About Measles-Mumps-Rubella (MMR) Vaccine and Autism
Q. What is autism?
Q. What causes autism?
The causes of autism are not known for certain. Most experts agree that autism is a condition that begins before birth. The current theory favored by many experts is that autism is a genetically based disorder. Studies of people with autism have identified abnormalities in brain structures that develop in the first few weeks of gestation (that is, while the fetus is in the womb).
Q. What is being done to make sure that vaccines stay safe?
The Centers for Disease Control and Prevention, the National Institutes of Health and the Food and Drug Administration continue to conduct studies to further ensure the safety of vaccines.For more information about immunizations, access the National Center for Immunization and Respiratory Diseases from the Centers for Disease Control and Prevention: http://www.cdc.gov/vaccines (Exit Site)
Q. Arent measles, mumps and rubella relatively harmless illnesses?
Q. Why should we still vaccinate against measles when cases are so uncommon?
Q. What are the complications of measles vaccination?
Q. Is there a link between measles vaccination and autism?
Q. What about Dr. Andrew Wakefields research claiming a link between MMR and autism?
Dr Wakefield's 1998 paper is simply a description of 12 children who were referred to his clinic because of diarrhea or abdominal pain. The 12 children also had a history of normal development followed by loss of certain skills. When a history was taken, questions were asked about MMR immunizations that had been administered as many as 9 years earlier and the relationship of these vaccines to onset of loss of skills. From these data, involving a small sample of children, Wakefield proposed an association between immunization and autism. Any association with MMR was based on parental recall about events that occurred many years earlier, instead of objective data. Further, in four of the 12 cases, the behavioral disorders predated the bowel symptoms, which refutes Wakefields own theory that bowel dysfunction (caused by MMR) causes autism. There was clearly selection bias as the children already had gastrointestinal symptoms. And there was no control group, a critical omission that casts further doubt on the findings. This was not a scientific paper but rather a description of parental recall from a skewed population of children referred to Wakefields clinic.
Replication of findings is a standard of good science. If research findings can be reproduced in a separate setting, it affirms those findings. Dr. Wakefields original research showed measles virus in Crohn's patients. He shared these specimens with his colleagues at Royal Free Hospital in London, who were then unable to find the measles virus using even more sensitive methods. Many other scientists examined intestinal biopsies of Crohn's patients and could not find measles virus. Wakefield's findings could not be replicated. His study was later retracted from the Lancet, where it was initially published.
Dr. Wakefields 2002 paper in the Journal of Molecular Pathology is also critically flawed. It claimed that 75 of 91 children with autism were found to have measles virus genome in intestinal biopsy tissue as compared with only 5 of 70 control patients. But we know that after the vaccine is given, the virus is likely to be taken up by specific immune cells and carried throughout the body (including the intestine). To determine if MMR is associated with autism, one must determine if the finding is specific for children with autism. Put differently, the control group must match the group of autistic children for immunization status and for the length of time between their MMR vaccine and their biopsy. This critical information was omitted from the paper.
A study by respected
researchers, published this year in the British Medical Journal, found
no rise in incidence of autism in children who received MMR as compared
to those who did not. The authors also showed that in autistic children,
the age at which a child received MMR did not affect the age at which
the diagnosis of autism was made. They also demonstrated that in the
years after the MMR vaccine was introduced in the United Kingdom, there
was no increase in autism rates in comparison to the years before the
vaccine was available.
A panel of experts
convened in June 2000, by the Academy, concluded in its report that
"separate administration of measles, mumps and rubella vaccines
to children provides no benefit over administration of the combination
MMR vaccine and would result in delayed or missed immunizations."
There is no scientific reason for or benefit to separating the vaccines. By separating them, we are putting children (and pregnant women who may be exposed to them) at increased risk by extending the amount of time they go unvaccinated.
This means that
pediatricians can and should feel confident using MMR vaccine and recommending
it for their patients, and parents can feel confident about it as well.
Last Updated: 3/18/2013