Usefulness of influenza vaccination during pregnancy to mothers and young infants.

As pregnant women are at increased risk of influenza infection and influenza-related complications, immunization with inactivated influenza vaccine during the influenza season is recommended. Vaccination during pregnancy is considered to provide benefits for both the mothers and their young infants. In 2009, the novel influenza A (H1N1) virus was reported worldwide to be the cause of a widespread outbreak of acute febrile respiratory illness. The efficacy and efficiency of monovalent vaccine against 2009 H1N1 influenza virus during pregnancy has already been confirmed in several studies. This article provides further useful information regarding the persistence of maternal antibodies and the transplacental transfer of antibodies following vaccination by comparison with natural influenza infection.