A new study, using insurance records for nearly 96,000 U.S. children, found no link between the measles - mumps – rubella (MMR) vaccine and autism – even among children who are at an increased genetic risk.
Experts are hoping that this study, along with several other studies on the risks of autism and the MMR vaccine, will reassure parents that the vaccine is safe.
While the original 1998 study associating the vaccine with autism has been found fraudulent, many parents continue to worry that the vaccine could be a trigger for autism; particularly parents that already have a child with autism.
"Research has shown that parents of kids with autism spectrum disorders are more likely to delay vaccinating their younger children," said Dr. Bryan King, an autism researcher at the University of Washington, in Seattle.
"Basically, they wait until the developmental dust has settled, and it looks like their child will be unaffected (by autism)," said King, who wrote an editorial published with the study.
Health officials are concerned that children who do not receive the MMR vaccine are putting other children at risk for serious diseases. They point to the recent measles outbreaks as one example. So far this year, 162 people have been sickened across 16 states and Washington D.C. according to the U.S. Centers for Disease Control and Prevention (CDC).
Scientists are working hard to find out why there has been an increase in autism over the last decade. It's known that genes make certain children more vulnerable to autism -- that's why kids with an affected older sibling are at higher-than-average risk. But environmental factors also have to play a role, experts believe.
Based on years of research, the MMR vaccine is not that trigger, according to health experts. "Every study that's looked at this, through every strategy they've used, has found no signal," King said.
According to King, it's natural for parents with a child who has autism to want to reduce their younger kids' risk.
"Everyone believes there have to be environmental factors contributing to the exponential rise we've seen in ASDs," he said. "But we don't understand what those factors are yet."
Researchers are finding clues, though. And more and more, they suspect that prenatal brain development is the critical period, King said.
The new findings are based on insurance records for nearly 96,000 U.S. children with an older brother or sister; 2 percent had an older sibling with an autism spectrum disorder.
Of the children with an affected sibling, 7 percent had an autism spectrum disorder themselves, compared to just under 1 percent of other kids. There was no evidence, though, that the MMR vaccination raised the risk of autism in either group of children, Jain said.
Among kids with an affected sibling, those who'd received one MMR dose by age 2 were actually one-quarter less likely to be diagnosed with an autism spectrum disorder, the study found. The odds were even lower among those who'd received two doses by age 5.
The study did not reveal any evidence that the MMR vaccine offered any protective influence over autism, only that it was not associated with an increase of risk for autism.
More studies are in the works to find the source of autism. Environmental factors are playing a key role in many of those studies as well as genetic links.
It’s understandable that parents would worry about vaccinations of any kind having a negative effect on their child, but more and more studies confirm that the MMR vaccine is one that parents can eliminate from their list of concerns.
This study was reported in the April 21 issue of the Journal of the American Medical Association.