Flu vaccine during pregnancy – unrelated to autism

There has been a general misconception that flu vaccine during pregnancy was not safe. Whether this was based on the general concerns about vaccines or something specific is difficult to determine. One of the worries was that getting a flu vaccine during pregnancy may cause a higher risk of autism in the baby.

We have tons of data that show us that vaccines are not related to autism spectrum disorder. Now we have another robust, large scale research study that establishes that autism is not link to flu vaccine during pregnancy.

Flu vaccine during pregnancy – the research


A team of researchers at Kaiser Permanente, an integrated health management consortium, published a new study in JAMA Pediatrics that attempted to answer, in part, whether there was any increased risk of autism after a mother received the flu vaccine during pregnancy. Kaiser is valuable to vaccine research since it manages all aspects of health of insured individuals allowing for easy access to short- and long-term data post vaccine. This is real epidemiological research as opposed to using a phone survey to obtain unsupported comments from parents.

The study examined the health records of nearly 200,000 children who were born at Kaiser Permanent facilities in Northern California between 2000 and 2010. They found that 3,101, or about 1.6%, had been diagnosed with autism through 2015. The age of diagnosis was between 2 and 15 years of age.

Since all of these children were diagnosed within the Kaiser system, we can make a reasonable assumption that the diagnostic criteria were reasonably consistent across all patients.

The researchers then looked at mothers’ health records to determine whether they had been diagnosed with flu or been given a flu vaccine. They found that less than 1% of these women contracted the flu, while about 23% received the flu vaccine while pregnant.

The researchers found the following:

  • Receiving the flu vaccine while pregnant does not appear to increase the risk of the baby being diagnosed with autism in later on.
  • Getting the flu while pregnant also does not appear to be linked with autism.
  • The rate of flu vaccination of pregnant women grew from 6% (wow) in 200 to 58% in 2010.

To be fair, the study did find a slight increase in risk of autism when mothers had a flu shot during the first trimester of pregnancy. If the risk would be assumed to be 16 out of 1000 births, then the increased risk of flu vaccine during the third trimester would be approximately 19 out of 1000. However, the error could be due to chance given the small numbers of children in that group and the multiple hypotheses the study tested. Since anti-vaccine types love to cherry pick data, I would predict that this will become a “thing,” except for the statistical fact that it is not a thing at all.

In case you were wondering, there were no effects were found during the second and third trimesters.

This study focused on the risks of autism from the flu or flu vaccine. One could conclude, from this data, that getting the flu vaccine or not would have little effect on the autism rate, which seems to be supported by the data. So why get the vaccine at all? Because contracting influenza has a negative outcome on other aspects of pregnancy:

Thanks to Andrew Wakefield, we have a evidence-free obsession with vaccines and autism. This wonderful study could have been used to look at other maternal outcomes to provide us with more data to convince mothers to get the flu vaccine during pregnancy. Instead, we have to continue to waste good research dollars chasing every possible angle to refute the crackpot hypothesis that vaccines are related to autism spectrum disorder.



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The Original Skeptical Raptor
Chief Executive Officer at SkepticalRaptor