The findings of new research ease concerns about the potential pregnancy risks of the flu vaccine, indicating that children exposed before birth face no greater risk of having developing autism.
In a study published this wee in the medical journal JAMA Pediatrics, researchers with Kaiser Permanente found no significant association between the flu vaccines during pregnancy and autism.
Researchers followed nearly 200,000 children born at Kaiser Permanente Northern California from January 1, 2000, to December 31, 2010. The children were born at a gestational age of at least 24 weeks.
Data on the mothers’ flu infection and flu vaccination was taken from the date of conception to their delivery date from Kaiser inpatient and outpatient databases. Any flu infections in the mothers were confirmed with positive influenza lab test results.
Autism spectrum disorder (ASD) diagnoses were recorded in electronic medical records on at least two occasions anytime from birth through June 2015.
Nearly 1,400 mothers received a flu diagnosis and about 45,000, or 23%, received flu vaccinations during pregnancy in 2000. In 2010, about 58% of mothers received flu vaccines. The average ages of vaccinated and unvaccinated women was 31 and 30 respectively.
A total of 3,100 children, or 1.6 percent, were diagnosed with autism spectrum disorder. Overall, researchers said maternal flu and flu vaccination was not associated with increased autism risk.
Researchers did indicate flu vaccines received in the first trimester was the only period associated with increased autism risk. But, study authors emphasized the link was not statistically significant and could be “due to chance,” as it was simply a “suggestion of increased ASD risk.”
Flu vaccines received in the second and third trimester were not associated with increased autism risk at all during this study.
Prior studies have suggested both genetic and environmental factors linked with increased autism risk. In recent years, concerns over vaccines and a link to autism have gained a significant amount of media attention. As a result, more studies have been launched to focus on possible links between autism and other causes.
However, much of the concern regarding the association between autism and vaccines came from a now-discredited study published in 1998 by Dr. Andrew Wakefield, who has been accused of having falsified data to make it appear that there was a connection.
Wakefield was stripped of his medical license in 2010 and his study was retracted and deemed a fraud, however, concerns over a connection between autism and vaccines persist.
Some studies have shown an association between maternal infections, maternal fever and autism risk. Many researchers were focused on the connection as flu infection and flu vaccination are associated with immune system activation.
This is the first study to investigate flu vaccine during pregnancy and autism risk. Previous studies have focused on vaccines received by children at an early age.