Prevalence of influenza A and B antibodies in pregnant women and their offspring.

BACKGROUND Influenza is associated with substantial morbidity and mortality in pregnant women and neonates, but few countries offer annual influenza vaccination with the inactivated vaccine to all women who are, or intend to become, pregnant. OBJECTIVES To provide seroepidemiological information on influenza A and B antibodies in pregnant women and their offspring in Germany. STUDY DESIGN Anti-influenza antibodies were determined using commercially available enzyme-linked immunosorbent assays (ELISA) on serum obtained from 209 women and their newborns at delivery. RESULTS The prevalence of antibodies against influenza A virus was 93.8% [89.6-96.6%] in the mothers and 96.7% [93.2-98.6%] in the newborns. The prevalence of antibodies against influenza B virus was 42.1% [35.3-49.1%] in the mothers and 78.5% [72.3-83.8%] in their newborns, which was a significant difference. The antibody concentrations against both influenza A and influenza B viruses were significantly lower in mother than in their newborns. CONCLUSIONS Because of active placental transport of IgG antibodies, neonates have higher prevalence and/or concentrations of influenza A and B virus-specific antibodies induced by natural infections than their mothers. Considering these serological findings, especially the lower prevalence of maternal antibody against influenza B virus, annual influenza vaccination may improve the protection of pregnant women and their offspring against influenza.