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Another large study finds no link between autism and vaccines — even among high-risk children

An analysis of all the data found that the children with an older sibling with autism were more likely to develop the condition — whether or not they were vaccinated.

Autism Occurrence by MMR Vaccine Status Among US Children

Yet another large study has found no link between the measles-mumps-rubella (MMR) vaccine and autism — even among children who have a higher-than-average risk for developing the neurological disorder.

Whether this study’s findings will help persuade parents who fear that vaccinations, especially MMR, can cause autism remains to be seen. In recent years, those fears have led some parents to reject vaccinations for their children — a trend that health officials say has resulted in an increasing number of outbreaks of potentially dangerous childhood diseases. One such outbreak began at Disneyland last December and sickened at least 117 people (by mid-April) in the United States, as well as several dozen more in Canada and Mexico.

This new study was conducted to address the concerns that some parents with a child affected by autism have about vaccinating younger siblings, who are at an increased genetic risk of developing the disorder. Surveys have shown that such parents are often reluctant to have the younger siblings vaccinated, fearing that a vaccine may have contributed to the older child’s autism. The authors of the new study, which was published Tuesday in JAMA, wanted to see if there is any basis for that fear.

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The answer is no.

“Taken together, some dozen studies have now shown that the age of onset of [autism spectrum disorder, or ASD] does not differ between vaccinated and unvaccinated children, the severity or course of ASD does not differ between vaccinated and unvaccinated children, and now the risk of ASD recurrence in families does not differ between vaccinated and unvaccinated children,” wrote Dr. Bryan H. King, a professor of psychiatry and behavioral sciences (and an autism specialist) at the University of Washington, in an editorial accompanying the study. 

A large database

For the study, researchers analyzed data collected from the health insurance records of almost 96,000 privately insured U.S. children born between 2001 and 2007. All the children had older siblings, for which health insurance data was also available.

By age 5, some 92 percent of the children without an older sibling with autism had received the MMR vaccine. That compared with 86 percent of the children who did have an affected older sibling.

The records also revealed that about 1 percent of the 96,000 children (994) were diagnosed with autism by age 5, and about 2 percent (1,929) had an older sibling diagnosed with the condition. Among this latter group of high-risk children, about 7 percent were diagnosed with autism themselves.

Key findings

An analysis of all the data found that the children with an older sibling with autism were more likely to develop the condition — whether or not they were vaccinated. 

Specifically, autism developed in 8.6 percent (23 of 269) of the high-risk children who weren’t vaccinated, compared to 3.8 percent (30 of 796) of the high-risk children who received two doses of the MMR vaccine.

Among the children not at high risk, 7,735 remained unvaccinated at age 5, and 56 of them (0.7 percent) were diagnosed with the condition. That compared to 244 of 45,568 children (0.5 percent) who received two MMR doses.

And, yes, this data does appear to show that the risk of developing autism was actually lower among the children — particularly the at-risk ones — who received the MMR vaccine. The authors caution, however, against interpreting that finding as suggesting that the vaccine is protective against autism. It could be, they write, that “parents who notice social or communication delays in their children decide to forestall vaccination.”

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‘No harmful association’

The study’s findings should be reassuring to all parents, not just those with high-risk children.

“We found that there was no harmful association between the receipt of the MMR vaccine and the development of an autism spectrum disorder,” said Dr. Jain Anjali, the study’s lead author and a pediatrics and health services researcher with the Lewin Group, in a video released by JAMA.

“We think these results attest to the promise of using big data to address public health questions of importance,” she added. “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 research funding can be directed at finding out what does cause autism spectrum disorders.”

The study can be read in full on the JAMA website. The study was funded by the National Institutes of Health and the U.S. Department of Health and Human Services. The Lewin Group is a health care consulting company associated with Minnesota-headquartered United HealthCare. According to its website, the Lewin Group “has established firm principles for preserving the integrity and editorial independence of work we deliver.” Its clients, however, include pharmaceutical companies as well as federal and state governments. That fact will undoubtedly be used by people skeptical of the effectiveness and safety of vaccines to discredit the study’s findings. That’s unfortunate, for this appears to be a well-designed study. 

JAMA news report on the study