Influenza vaccine in pregnancy: no increase in birth defect risk?

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  • Large observational study shows no increased risk for major structural birth defects in offspring after maternal first trimester inactivated influenza vaccine (IIV) vaccination.

Why this matters

  • Data should provide reassurance for women considering first trimester vaccination.

Study design

  • Observational study.
  • Pregnant women with live-born singletons at 7 Vaccine Safety Datalink sites.
  • Infants followed for 1 y.
  • First trimester IIV exposure defined as receipt before 14 wk of gestation.
  • Primary outcome was presence of 1 or more of more than 50 prespecified major structural birth defects.
  • Funding: CDC.

Key results

  • 425,944 mother–infant pairs, of whom 12% received first trimester IIV (exposed).
  • Ma...