(RxWiki News) The cause of autism remains a mystery, but new evidence may rule out one possible cause — bringing researchers closer to understanding this disorder.
A new study found that children who received the measles-mumps-rubella (MMR) vaccine in the first years of life did not have an increased risk of autism spectrum disorders (ASD), regardless of whether their siblings had ASD.
"Consistent with studies in other populations, we observed no association between MMR vaccination and increased ASD risk among privately insured children," wrote lead study author Anjali Jain, MD, of the Lewin Group in Falls Church, VA, 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."
This study looked at more than 95,000 US children insured under a large health plan, along with their older siblings. Patients were enrolled in the plan from birth to at least 5 years of age between 2001 and 2012. A little over 2 percent of the children had an older sibling with ASD.
About 1 percent of the children were diagnosed with ASD during follow-up. Those who had older siblings with ASD were diagnosed more often than children whose siblings did not have the disorder.
However, the MMR vaccine was not tied to an increased risk of ASD at any age, Dr. Jain and team found. In fact, MMR vaccination rates for children with older siblings with ASD were lower than those for children from unaffected families.
"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 undervaccinated in our observations as well as in previous reports," Dr. Jain and team wrote.
The Centers for Disease Control and Prevention recommends two doses of MMR vaccine for US children: the first at age 12 to 15 months and the second at age 4 to 6 years.
"Lower vaccination levels threaten public health by reducing both individual and herd immunity and have been associated with several recent outbreaks of measles, with most cases occurring among unvaccinated individuals," Dr. Jain and colleagues noted.
Still, some parents continue to worry. Families with a child affected by autism, a developmental disorder that affects communication and interaction, may be more concerned about reports linking the vaccine to ASD, these researchers noted. Dr. Jain and team said they hoped their findings would allay these fears.
"Controversy seems to follow autism like the tail on a kite," wrote Bryan H. King, MD, of the Seattle Children's Autism Center, in an editorial about this study. "... As long as there are swirling winds, the kite will have a tail, and to be fair, controversy can be a stimulus for progress. These studies move the field forward toward a more focused and productive search for temporal and environmental factors that contribute to autism risk. They also provide information to support families affected by autism — either by allaying concern that MMR vaccine might be harmful or giving parents the knowledge and tools to better understand their child's condition and manage his or her behavior. The field is long overdue for calm weather, and the forecast is increasingly promising."
The study and editorial were published April 21 in JAMA.
The National Institutes of Health and the US Department of Health and Human Services funded this research. Some of the authors received funds from the Lewin Group and Optum.