Study Finds No Link Between Flu Vaccine and Autism

Mothers-to-be can soothe their fears about getting a flu shot – a new study shows that there’s no link between receiving a flu vaccine during pregnancy and the child’s risk of being diagnosed with autism later in life.

The large study, led by researchers at Kaiser Permanente in Northern California, tracked the health records of more than 196,000 children born in California between 2000 and 2010. While the researchers noted a 1.6 percent incidence of autism among the children they studied, they failed to find a link between a mother’s flu vaccine and autism rates.

“There was no association between maternal influenza infection anytime during pregnancy and increased [autism spectrum disorder] risk,” wrote the researchers in JAMA Pediatrics.

“This large study is reassuring for expectant mothers. The way we feel people should interpret this is that there is really not any increased risk for autism, and we’re recommending no changes in the vaccine policy,” said Lisa Croen, the study’s lead author.

However, the authors were quick to point out that some statistical variation occurred when mothers received a flu shot during their first trimester.

“There was a suggestion of increased ASD risk among children whose mothers received an influenza vaccination in their first trimester, but the association was not statistically significant after adjusting for multiple comparisons, indicating that the finding could be due to chance,” the study authors wrote.

“These findings do not call for changes in vaccine policy or practice, but do suggest the need for additional studies on maternal influenza vaccination and autism,” they reported.

Focusing on the Health of the Mother and Child

The flu virus often affects pregnant women far more harshly than it does women who are not pregnant, notes the Centers for Disease Control and Prevention (CDC). The flu can lead to “serious problems” for the developing baby, such as premature labor and delivery.

“We know that pregnant women are particularly vulnerable,” Croen said. “There are lots of changes in their immune system and lungs and heart. It’s especially important to protect pregnant women against the flu.”

While the CDC reports that about 50 percent of mothers-to-be received the flu vaccine last year, the health agency encourages more women to receive the flu shot to protect themselves and their child’s health.

Previous studies have suggested a link between infections in pregnant women and the risk of their children developing autism spectrum disorder. “While two previous studies found associations between maternal influenza and increased ASD risk, others did not,” report the study authors.

The researchers note that “animal studies show an association between maternal immune activation during pregnancy and behavioral and brain abnormality in offspring, similar to those observed in children with ASD.”

While this is the first study to investigate the relationship between maternal vaccinations and ASD risk, prior research suggests that avoiding infections is paramount to the child’s health. “Pregnant women are encouraged to get vaccinated against influenza because they face an increased risk of complications from the infection,” the authors report.