In years past, pregnancy was also a contraindication to flu vaccine but, today, the CDC recommends flu vaccine for all pregnant women.
Initially, most influenza vaccines were classified as Category B or C drugs, which meant that adequate and well-controlled studies on pregnant women had not been conducted and it was not known whether these vaccines could cause fetal harm when administered to a pregnant woman or if they could affect reproduction capacity.
In 2015, the FDA removed pregnancy categories due to concerns of confusion and oversimplification and replaced it with the Pregnancy and Lactation Labeling Rule. This rule affects all influenza vaccine products submitted for approval after June 30, 2015. As new language is phased in, information on risks associated with vaccinating while pregnant will appear in 8.1 of each vaccine’s package insert under Risk Summary. NVIC encourages consumers read this information carefully prior to receiving a vaccine.
Prior to the FDA licensing of all influenza vaccines, drug companies did not test the safety and effectiveness in pregnant women and little data is available on biological responses to these vaccines that could affect pregnancy and birth outcomes.
Pregnant women should also be aware that the multi-dose flu vaccine contains thimerosal, which is a mercury derivative. Mercury is toxic to the brain and has been found to be associated with brain damage and developmental delays in babies whose mothers were exposed to high levels of mercury during pregnancy.
In December 2016, Congress signed the 21st Century Cures Act into law. This new law protects vaccine manufacturers from lawsuits in civil court if an FDA licensed vaccine given to a pregnant woman causes the injury or death of her unborn child in the womb. As a result, policies relating to compensating vaccine injuries sustained by an unborn child in the womb are being developed.
In 2017, a CDC funded study reported that women vaccinated in the early part of their pregnancy with a flu vaccine containing the pandemic H1N1 (H1N1pdm09) strain and who also had been previously vaccinated the prior season with a H1N1pdm09-containing flu vaccine had a greater risk of miscarriage in the first four weeks following vaccination. The CDC conducted further research among women who were pregnant during the 2012-2013 through 2014-2015 flu seasons and eligible to receive the flu vaccine. This study, which contradicted their previous findings, reported that the influenza vaccine did not cause miscarriages in the women evaluated in the study.
