A massive Danish study out Tuesday adds some of the most convincing evidence yet that parents should not fear vaccinations, as measles cases hit alarming levels around the world.
The measles cluster in Washington State — the worst outbreak in two decades — and elsewhere can be partly blamed on a moral panic among parents who skip vaccinations because they think it’ll result in their kids being diagnosed with autism or other disorders.
But the new study found no connection between the measles vaccination and an increased risk for autism. If anything, unvaccinated kids might be more linked to the developmental disorder, researchers led by epidemiologist Anders Hviid at the Staten Serum Institute in Copenhagen wrote.
The study, published in the Annals of Internal Medicine on Tuesday, collected population data — vaccinations, diagnoses and family history — on 657,461 children born in Denmark from 1999 through the end of 2010. Of those children, 6,517 were diagnosed with autism during the course of the study.
There was no increased risk for autism among children who had received the vaccination, the researchers found. The kids who’d gotten the measles, mumps and rubella (MMR) vaccination appeared 7 percent less likely to be linked with autism than the children who weren’t vaccinated. Children with zero childhood vaccinations were 17 percent more likely to be linked with autism.
However, as previous studies have shown, that might be because parents are less likely to vaccinate their kids after they start showing symptoms of autism. That’s put autistic kids at greater risk for contracting vaccine-preventable diseases like measles.
"The study strongly supports that MMR vaccination does not increase the risk for autism," the authors said. "We believe our results offer reassurance and provide reliable data."
The study wasn’t a controlled experiment on whether vaccinations do or do not cause autism, so there wasn’t a control group — it would be unethical to intentionally forgo vaccinating children for research purposes. Overall, 95 percent of the kids in the study received the MMR vaccine.
But the massive study adds to a growing body of evidence that parents shouldn’t fear vaccinations. Such parents and anti-vaccination groups routinely cite a flawed, retracted 1998 paper that linked autism diagnoses and vaccines. The 1998 study’s author, Andrew Wakefield, is no longer allowed to practice medicine and has become a prominent anti-vaccination activist.
“Despite many subsequent studies not finding an association between MMR vaccine and autism, public concerns regarding a potential link between MMR vaccine and the development of autism have persisted,” researchers with Emory University wrote in an accompanying editorial.
The study also echoed findings discovered through prior research on autism: Kids with autistic siblings are more likely to be diagnosed with the disorder, and it’s more likely to occur in boys. But even among children with increased risk factors, getting the measles vaccine didn’t seem to make a difference, the researchers wrote.
From the start of this year through February 28, more than 200 people have been diagnosed with measles — a once-eradicated virus — across 11 states, according to the U.S. Centers for Disease Control and Prevention. The bulk of the cases are in Vancouver, Washington, near the Oregon border, primarily among children. Since the start of the outbreak, Washington has spent more than $1.2 million trying to contain it. There’s also an ongoing measles outbreak in New York City, where some members of the Orthodox Jewish community claim religious exemptions against vaccinations.
Legislators in D.C. are now moving forward with a bill that would make the measles vaccine mandatory, as people in the state can currently claim “philosophical” exemptions. Hundreds of parents against vaccinations have protested the potential rule change, though.
Cover: Jocelyn Smith cares for her 11-month-old son, Mason, at their home in Camas, Washington, on Wednesday, Jan. 30, 2019. Smith has been afraid to take Mason out of the house during a measles outbreak in southwest Washington because he is too young to receive the measles vaccine. The measles outbreak has sickened 39 people, with 13 more cases suspected, since Jan. 1. (AP Photo/Gillian Flaccus)