Despite over a decades’ worth of research that have found no association between the measles vaccine and autism, some parents still refuse to immunize their children. Well, here’s a new study from the Journal of the American Medical Association (JAMA) that says, again, there’s no link. And this time, they looked at insurance claims for more than 95,000 children, some of whom have older siblings with autism spectrum disorders (ASD).
As of April 17, there are 162 measles cases in 19 states and Washington D.C. this year. Almost three-fourths of these are linked to the Disneyland outbreak in California, with initial exposures taking place this past December. Many of the people who got measles were unvaccinated, though not all by choice—such as infants too young to receive the measles-mumps-rubella (MMR) vaccine. The U.S. Centers for Disease Control and Prevention (CDC) recommends two doses for all children. The first dose can be administered as early as 12 months of age, and the second should be given when the kid is between 4 and 6 years old. Together, the two doses are 97 percent effective.
A team led by Anjali Jain of healthcare consulting firm The Lewin Group in Virginia sorted through records from the Optum Research Database, which included health-plan participants living throughout the country. They focused on 95,727 children with older siblings. Of these children, just over 1 percent have been diagnosed with ASD, while 2 percent have older siblings with ASD. There were 134 children with autism whose siblings also have autism. Children with older siblings who have autism are sometimes thought to have an increased risk themselves. And because parents who have a child with ASD may be especially wary of vaccinations, it was particularly important to look at these younger siblings, Jain tells the Wall Street Journal.
The team also looked at MMR vaccination rates. By the time they were 2 years old, 84 percent of children with unaffected older siblings had been vaccinated, and by the time they were 5 years old, 92 percent had received at least one shot. On the other hand, of the children whose older siblings have autism, 73 percent were vaccinated by age 2, and 86 percent were vaccinated by age 5.
The researchers then calculated and compared the relative risk of ASD for all of the nearly 96,000 children, at ages 2 and again at 5, and for no vaccine versus 1 and 2 vaccine doses. The results are very number heavy, but their conclusion is this: Receiving the MMR vaccine did not increase the children's risk of ASD, regardless of whether or not the older siblings have it.