Another Study Confirms No Link Between MMR Vaccine, Autism

The measles-mumps-rubella (MMR) vaccine was not associated with autism spectrum disorder (ASD)—even among children at risk for autism by virtue of having an older sibling with autism—in a large sample of privately insured children.

The study, appearing online April 21 in JAMA, joins an already large body of research showing no association between childhood vaccines and autism. Nevertheless, some parents have opted to forego the vaccine with the result that there have been isolated outbreaks of measles.

“Consistent with studies in other populations, we observed no association between MMR vaccination and increased ASD risk among privately insured children,” said lead author Anjali Jain, M.D., of the Lewin Group and colleagues. “We also found no evidence that receipt of either one or two doses of MMR vaccination was associated with an increased risk of ASD among children who had older siblings with ASD. As the prevalence of diagnosed ASD increases, so does the number of children who have siblings diagnosed with ASD, a group of children who are particularly important as they were under-vaccinated in our observations as well as in previous reports.”

They conducted a retrospective cohort study using an administrative claims database associated with a large commercial health plan. Participants included children who had been continuously enrolled in the health plan from birth to at least 5 years of age in the years 2001 to 2012 and also had an older sibling continuously enrolled for at least six months between 1997 and 2012.

They looked at receipt of the MMR vaccine (0, 1, 2 doses) between birth and 5 years of age; and ASD status was defined as two claims with a diagnosis code in any position for autistic disorder or other specified pervasive developmental disorder (PDD) including Asperger’s syndrome or unspecified PDD (according to ICD-9).

Out of 95,727 children in the cohort, 994 (1.04 percent) children had ASD diagnosed during follow-up and 1,929 (2.01 percent) had an older sibling with ASD. There was no statistically significant risk for ASD associated with the MMR vaccine at any age in either group of children—those who did and did not have an older sibling with autism.

“These findings indicate no harmful association between MMR vaccine receipt and ASD even among children already at higher risk for ASD,” the authors state.

Louis Kraus, M.D., chair of the APA Council on Children, Adolescents, and Their Families, told Psychiatric News that the findings are redundant evidence that childhood vaccines are safe. Yet the belief that vaccines may be related to autism has persisted.

“This study further supports that there is no correlation between the MMR vaccine and developing autism,” he said in an interview. “Parents need to consult with their primary care physicians and pediatricians and follow the recommendations of the American Academy of Pediatrics to immunize their children.”

Kraus noted that even relatively small numbers of children who are not vaccinated can diminish “herd immunity”—the protection of the entire population against disease when a large enough proportion of the population is immunized that the spread of disease is impossible even to those who are not immunized.

“It is understandable that with the steady increase in the diagnosis of autism, people look for an environmental fact,” Kraus said. “But the reality is that we have had no research to support an environmental cause, and none at all to link the MMR vaccine to autism.” ■

“Autism Occurrence by MMR Vaccine Status Among U.S. Children With Older Siblings With and Without Autism” can be accessed here.