Immunizing pregnant women against influenza confers passive protection to their infants but only through the first 8 weeks of life, according to the largest randomized trial of seasonal influenza vaccination during pregnancy (Nunes MC et al. JAMA Pediatr. doi:10.1001/jamapediatrics.2016.0921 [Published online July 5, 2016]).
This study was a secondary analysis of a randomized, placebo-controlled clinical trial on the safety, immunogenicity, and infant and maternal efficacy of trivalent inactivated influenza vaccine (IIV3) during pregnancy (Madhi SA et al. N Engl J Med. 2014;371:918-931). For the secondary analysis, investigators assessed the duration of vaccine efficacy against confirmed influenza in 1026 infants born to women immunized with IIV3 and 1023 infants born to women who received placebo.
Slomski A. Limited Infant Protection From Maternal Influenza Immunization. JAMA. 2016;316(8):809. doi:10.1001/jama.2016.10786