Influenza Vaccine Immunogenicity: Pregnancy and Postpartum

Despite recommendations that all pregnant women receive influenza immunization, vaccination rates remain low, and the response to this vaccine during pregnancy has not been well studied. Investigators report immunogenicity rates for pregnant women at a single academic center during influenza seasons from October 2006 through January 2010.

Overall, 239 pregnant women received the trivalent vaccine, the 2009 monovalent vaccine against pandemic H1N1 influenza, or both. Blood was drawn before vaccination and 4 to 8 weeks after vaccination. Seroconversion was defined as at least a fourfold rise in hemagglutination inhibition geometric mean titers, and seroprotection as a hemagglutination inhibition titer of 1:40 or higher. The rates of seroconver…