Is the Inactivated Influenza Vaccine Safe During Pregnancy?

It is safe for pregnant women to receive both the inactivated influenza vaccine (IIV) and pertussis vaccine at any point during their pregnancy, according to a new study. Doing so does not elevate the risk for adverse birth outcomes.

To reach this conclusion, the researchers compared the birth outcomes for women vaccinated with IIV during their pregnancy with those who had not been vaccinated. In all, data on 8827 participants from the Australian “FluMum” (2012–2015) study were analyzed.

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For this study, adverse birth outcomes were defined as preterm birth, low birthweight at term, and small for gestational age.

With hazard ratios of 1.10 for preterm births, 1.05 for low birthweight at term, and 0.99 for small for gestational age, the participants who had received IIV during pregnancy did not have an elevated risk for an adverse birth outcome compared with those who were not vaccinated during pregnancy.

The researchers then conducted a sensitivity analysis among a subgroup of participants who had received the pertussis vaccination during pregnancy. In doing this, the researchers confirmed that the associations between IIV and adverse outcomes were maintained, with the adjustment for the pertussis vaccination yielding similar results.

There was also no evidence of elevated risk by trimester of IIV.

—Colleen Murphy

Reference:

McHugh L, Marshall HS, Perrett KP, et al. The safety of influenza and pertussis vaccination in pregnancy in a cohort of Australian mother-infant pairs, 2012–2015: the FluMum Study. Clin Infect Dis. 2019;68(3):402-408. https://doi.org/10.1093/cid/ciy517.