Researchers from Kaiser Permanente Northern California (Oakland) examined 196,929 births and analyzed for associations between influenza and autism spectrum disorder (ASD).

The study sample included 1,400 mothers who had been diagnosed with influenza and 45,231 mothers who had received a flu vaccination during pregnancy. Of all the births, 3,101 children, or 1.6%, were diagnosed with ASD.

The study did not find any association between a risk of ASD in offspring and influenza vaccination during pregnancy.

During the second and third trimesters of pregnancy, the researchers found no association, but the results suggested a very slight association between flu vaccination and ASD in the third trimester. However, the authors emphasize that the association did not prove to be statistically significant after multiple adjustments, indicating that it was due to chance.