Influenza Vaccine Safety Considerations during Pregnancy or while Breastfeeding

Table of Contents

Background

Influenza (flu) during pregnancy is more likely to cause illness that results in hospitalization. Influenza also may be harmful for the developing baby. A common influenza sign can be fever, which has been associated in some studies with neural tube defects and other adverse outcomes for a developing baby. Getting vaccinated while pregnant can also help protect a baby from influenza after birth (because antibodies are passed to a developing baby during pregnancy). When you get an influenza vaccine while pregnant or breastfeeding, your body develops antibodies against influenza that are shared with your baby through breast milk.

An influenza vaccine is the best protection against influenza

Getting an influenza vaccine is the first and most important action a person can take to protect against influenza and its potentially serious complications. If you are pregnant, you should get an injectable influenza vaccine (shot) and not the nasal spray influenza vaccine. A 2013 study showed that during the 2010–2011 and 2011–2012 influenza seasons vaccination reduced the risk of influenza during pregnancy by up to 50%. These results are consistent with the general range of estimated influenza vaccine effectiveness among adults 18-64 years. A 2018 study showed that getting an influenza shot during pregnancy reduced the risk of being hospitalized with influenza by an average of 40%. Getting an influenza shot during pregnancy also helps to protect babies from influenza illness for the first several months after their birth, when they are too young to get vaccinated. A list of recent studies is available at benefits of influenza vaccination during pregnancy. September and October are generally good times to be vaccinated each year. Early vaccination during July and August also can be considered during the third trimester of pregnancy.

CDC’s Advisory Committee on Immunization Practices (ACIP) and the American College of Obstetricians and Gynecologists recommend that all adults receive an annual influenza vaccine. If you are or will be pregnant during influenza season, you should receive an inactivated influenza vaccine (you should not receive a live attenuated influenza vaccine during pregnancy) as soon as it is available. Influenza shots have been given to millions of women during their pregnancies for more than 50 years with an excellent safety record. There is substantial evidence that influenza shots are safe during pregnancy for mom and baby. CDC and ACIP recommend influenza vaccination during any trimester of pregnancy.

Getting an influenza vaccine while pregnant does not increase the risk of miscarriage or stillbirth

CDC’s Vaccine Safety Datalink (VSD) project conducted one of the largest studies examining influenza vaccination and risk of miscarriage. The study covered three influenza seasons (2012–2013, 2013–2014, 2014–2015), looking for any increased risk for miscarriage among those who had received an influenza vaccine during their pregnancy. The study found no increased risk of miscarriage associated with influenza vaccination during pregnancy. This study was a follow-up to a previous smaller study that suggested pregnant women who received H1N1-containing influenza vaccine two years in a row might have an increased risk of miscarriage. The more recent results from this larger study showed that influenza vaccination was safe for pregnant women and their unborn babies and support the current ACIP recommendation for influenza vaccination at any time during pregnancy. Another study in the VSD (Panagiotakopoulos et al. 2020

Studies

Earlier studies that support the safety of influenza vaccination during pregnancy include:

Reviews of reports to the Vaccine Adverse Event Reporting System
(VAERS) (Moro et al, 2011
and Moro et al, 2017
A study using VSD data (Irving et al, 2013
) found no increased risk of miscarriage among pregnant women who received influenza vaccines in the 2005–06 or 2006–07 flu seasons.
A large study using VSD data (Kharbanda et al, 2013
) found no increased risk for adverse obstetric events such as chorioamnionitis, pre-eclampsia, or gestational hypertension among pregnant women who received an influenza vaccine from 2002 to 2009 when compared to pregnant women who were not vaccinated.
A VSD study (Nordin et al, 2014
) compared pregnant women who received an influenza vaccine during the 2004-05 and 2008-09 influenza seasons with an equal number who did not. The study found that rates of premature delivery or small for gestational age infants were the same for both groups.
A large August 2017 study using VSD data
found that the babies of women vaccinated during their first trimester had no increased risk of major birth defects.