Impact of postpartum influenza vaccination of mothers and household contacts in preventing febrile episodes, influenza-like illness, healthcare seeking, and administration of antibiotics in young infants during the 2012-2013 influenza season.

BACKGROUND Influenza is associated with an increased risk for serious illness, hospitalization, and mortality in infants aged <6 months. However, influenza vaccines are not licensed for administration in this age group. The study evaluated the effectiveness of postpartum influenza vaccination of mothers and household members in infants. METHODS The influenza vaccine was offered to mothers and household members of neonates born or hospitalized in 3 hospitals prior to the 2012-2013 season. Mothers were contacted every 2 weeks during the influenza season, and data regarding the onset of fever and/or respiratory symptoms in infants, healthcare seeking, hospitalization, and administration of antibiotics were collected. RESULTS The study group consisted of 553 mothers who delivered 573 neonates. The influenza vaccine was administered to 841 of 1844 (45.6%) household contacts. Vaccination coverage rates ranged between 41.9% for neonates siblings and 49% for mothers. Five hundred thirty infants were analyzed for vaccine effectiveness. For outcomes in the infant, postpartum maternal vaccination had 37.7% effectiveness against acute respiratory illness (ARI), 50.3% against a febrile episode, 53.5% against influenza-like illness (ILI), 41.8% against related healthcare seeking, and 45.4% against administration of antibiotics. Multiple logistic regression analyses showed that maternal influenza vaccination was significantly associated with a decreased probability for febrile episodes, ARIs, and/or ILIs in infants, related healthcare seeking, and/or administration of antibiotics during the influenza season. Vaccination of other household contacts had no impact. CONCLUSIONS Maternal postpartum vaccination against influenza was associated with a significant reduction of influenza-related morbidity, healthcare seeking, and antibiotic prescription in infants during the influenza season.