Maternal influenza vaccination during pregnancy protects infants against flu during their first six months of life.
Young children are at higher risk of complications from infection with the influenza virus but are ineligible to be vaccinated until age 6 months.
Angelia A. Eick of the Armed Forces Health Surveillance Center and colleagues conducted a non-randomized observational cohort study on Navajo and White Mountain Apache Indian reservations, where children have a higher rate of severe respiratory infection than the general population.
A group of 1,169 women who delivered babies during one of three influenza seasons completed questionnaires about demographics, vaccination status of all family members and flu risk factors.
A total of 1,160 mother-infant pairs then gave blood samples that were assessed for flu antibody presence. Mothers completed a second questionnaire at the end of the flu season and surveillance was conducted throughout to track new influenza-like illnesses.
During the flu season following their birth, 193 (17 percent) of infants were hospitalised for influenza-like illness, 412 (36 percent) had only an outpatient visit for a respiratory cause and 555 (48 percent) had no flu- or flu-like episodes.
Infants whose mothers were vaccinated had a 41 percent lower risk of laboratory-confirmed influenza virus infection and a 39 percent reduced risk of hospitalisation from influenza-like illness. In addition, those with blood samples available had higher levels of flu antibodies at birth and at 2 to 3 months than babies born to unvaccinated women.
"These findings are particularly relevant with the emergence of 2009 pandemic influenza A (H1N1) virus, which had a substantial impact on pregnant women and high hospitalisation rates among young infants," the authors wrote.
Justin R. Ortiz and Kathleen M. Neuzil of the University of Washington wrote: "The burden of influenza among pregnant women, the excellent safety profile of the vaccine and the reliable immunogenicity of trivalent inactivated influenza vaccine in this group support a recommendation that all pregnant women receive influenza vaccine to decrease complications of influenza disease during their pregnancies."
"The additional benefits of maternal influenza vaccination to the newborn, as demonstrated in the Bangladesh and White Mountain and Apache Navajo communities, should catalyze efforts to improve vaccination rates in countries with existing maternal immunization recommendations," they concluded.
The findings were published in the Archives of Pediatrics and Adolescent Medicine, one of the JAMA/Archives journals.