What is the relationship between MMR vaccine and autism in children? What do studies show?

By Al Saint Jacques, MDLinx
Published December 11, 2015

Key Takeaways

Although research has demonstrated that there is no link between the measles-mumps-rubella (MMR) vaccine and autism spectrum disorders (ASD), there are still beliefs that the vaccine causes autism, thus leading to lower vaccination levels. Parents who already have a child with ASD may be especially concerned about vaccinations. A recent trial to report the occurrence of ASD by MMR vaccine status was performed in a large sample of US children who have older siblings with and without ASD. The results showed that vaccination with the MMR vaccine was not associated with increased risk of ASD, regardless of whether older siblings had ASD. These findings indicate that there is no harmful association between MMR vaccine receipt and ASD even among children already at higher risk for ASD, according to a recent report published in the Journal of the American Medical Association.

"We have been studying health outcomes in children with autism spectrum disorders and in their family members for that last 5 years," explained lead author Dr. Anjali Jain of The Lewin Group in Falls Church, Virginia. "We have been able to use a very large claims-based data set in order to study these outcomes. A large database is very important for a condition like ASD because the condition varies so much from child to child. We were partucularly interested in this question because although there is a lot of research suggesting that there is no link between MMR vaccine and ASD, those beliefs continue to persist."

A retrospective cohort study was performed using an administrative claims database associated with a large commercial health plan. Study participants included children continuously enrolled in the health plan from birth to at least 5 years of age during 2001-2012 who also had an older sibling continuously enrolled for at least 6 months between 1997 and 2012.

"For this study, we wanted to compare the risk of developing ASD in children who receive the MMR vaccine compared with those who did not," Dr. Jain noted. "We were particularly interested in assessing this risk in children who had an older sibling with ASD who were thus at increased risk of developing ASD themselves."

Results showed that of 95,727 children with older siblings, 994 (1.04%) were diagnosed with ASD and 1929 (2.01%) had an older sibling who had ASD. Of those with older siblings with ASD, 134 (6.9%) had ASD, vs 860 (0.9%) children with unaffected siblings. MMR vaccination rates (≥1 dose) were 84% (n = 78?564) at age 2 years and 92% (n = 86?063) at age 5 years for children with unaffected older siblings, as opposed to 73% (n = 1409) at age 2 years and 86% (n = 1660) at age 5 years for children with affected siblings.

The researchers noted that MMR vaccine receipt was not associated with an increased risk of ASD at any age. For children with older siblings with ASD, at age 2, the adjusted relative risk (RR) of ASD for 1 dose of MMR vaccine vs no vaccine was 0.76, and at age 5, the RR of ASD for 2 doses compared with no vaccine was 0.56. For children whose older siblings did not have ASD, at age 2, the adjusted RR of ASD for 1 dose was 0.91 and at age 5, the RR of ASD for 2 doses was 1.12.

"We found that there was no harmful association between the receipt of the MMR vaccine and the development of an autism spectrum disorder," Dr. Jain reported. "In the study itself about 1% or just under 1,000 kids were diagnosed with an autism spectrum disorder. The risk of developing an ASD was higher in those kids who had an older sibling with an autism spectrum disorder, but there was no association between the MMR vaccine and ASD irrespective of whether or not the kids had an older sibling with an ASD themselves. The study also confirmed that children who had an older sibling with an autism spectrum disorder were less likely to be vaccinated with the MMR vaccine compared to those kids who had unaffected siblings. Thier vaccination rates were about 10% less than kids with unaffected siblings."

She went on to explain, "we think these results attest to the promise of using big data to address public health questions of importance. We hope to continue this work both for children with autism and their family members as well as potentially for other conditions. We also hope that more funding can be directed toward what does cause autism spectrum disorders."

Other authors in the study included Jaclyn Marshall, MS, and Jonathan P. Kelly, MPP, of The Lewin Group; Ami Buikema, MPH, and Tim Bancroft, PhD, of Optum in Eden Prairie, Minnesota; and Craig J. Newschaffer, PhD, of the AJ Drexel Autism Institute at Drexel University in Philadelphia, Pennsylvania.

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