A study published Tuesday in JAMA investigated the association between maternal influenza infection and vaccination and the risk of autism spectrum disorder (ASD), and concluded that the association was statistically insignificant after adjusting for confounders.
The large cohort study (196929 children, 3103 of which had ASD) of participants born at Kaiser Permanente in northern California between 2000 and 2010, collected patient data from Kaiser . The researchers investigated the link between either a positive lab for flu or a flu vaccination date during pregnancy, and diagnosis of ASD.
Covariates examined were sex, year of conception, maternal pre pregnancy BMI, maternal age at delivery, maternal education, maternal race, gestational diabetes, maternal asthma, hypertension, autoimmune disease, and allergies.
The covariates of male sex of the baby and preterm birth, as well as older age and high education, asthma, autoimmune disease, gestational diabetes, and hypertension in the mother were all associated with increased risk of ASD diagnosis. Controlling for these covariates, the researchers concluded that maternal influenza or vaccination during pregnancy was not associated significantly with increased risk of ASD diagnosis (irrespective of trimester of infection).
Note: after adjustment, maternal flu vaccination was not associated significantly with ASD risk. Maternal flu infection in the first trimester was associated with an increased risk of ASD. However, after correcting the p-value for the multiple hypotheses using Bonferroni correction, the link between flu infection and ASD risk became insignificant.
The researchers conclude that there are no associations between ASD risk and flu infection during 2nd and 3rd trimester or flu vaccine during pregnancy. They do not advocate changing the current vaccine policy, but they do call for further study of ASD and first trimester infection.