Prevention of influenza-related illness in young infants by maternal vaccination during pregnancy.

The influenza virus circulates yearly and causes global epidemics. Influenza infection affects all age groups and causes mild to severe illness, and young infants are at particular risk for serious disease. The most effective measure to prevent influenza disease is vaccination; however, no vaccine is licensed for use in infants younger than 6 months old. Thus, there is a crucial need for other preventive strategies in this high-risk age group. Influenza vaccination during pregnancy protects both the mothers and the young infants against influenza infection. Vaccination during pregnancy boosts the maternal antibodies and increases the transfer of immunoglobulin G from the mother to the fetus through the placenta, which confers protection against infection in infants too young to be vaccinated. Data from clinical trials and observational studies did not demonstrate adverse effects to the mother, the fetus, or the infant after maternal influenza vaccination. We present the current data on the effectiveness and safety of influenza vaccination during pregnancy in preventing disease in the young infant.