JAMA Logo Influenza vaccines provided to expecting mothers seem to benefit their future children. A recent study suggests that babies of mothers receiving influenza vaccines while pregnant face less risk of been infected with flu or hospitalized for respiratory illnesses in the first six months of life. It is known that infants are more susceptible to complications developed from infection with the influenza virus, but babies can be vaccinated only after the age of 6 months.

The frequency of influenza virus infection in infants is apparently more among babies aged 6 to 12 months than in the first six months of life. However, this risk may be avoided by maternal influenza antibodies acquired transplacentally or through breastfeeding. It was noted that during severe influenza seasons, morbidity and mortality rates among infants younger than 6 months exceed as compared to those of older babies. A non-randomized observational cohort study was triggered on Navajo and White Mountain Apache Indian reservations, where children seemingly have a higher rate of severe respiratory infection than the general population.

Scientists highlight, “Although influenza vaccination is recommended for pregnant women to reduce their risk of influenza complications, these findings provide support for the added benefit of protecting infants from influenza virus infection up to six months, the period when infants are not eligible for influenza vaccination but are at highest risk of severe influenza illness. 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 hospitalization rates among young infants.”

Authors made 1,169 women fill in questionnaires about demographics, vaccination status of all family members and flu risk factors. This group of women had delivered babies during one of the three influenza seasons. Participants provided their blood samples which were evaluated for presence of flu antibody. A second questionnaire was completed by study subjects at the end of flu season. Throughout the study Angelia A. Eick, Ph.D., then of Johns Hopkins Bloomberg School of Public Health, Baltimore, and now of the Armed Forces Health Surveillance Center, Silver Spring, Md., and colleagues closely monitored new influenza-like illnesses. At the time of flu season after birth, 193 infants forming 17 percent were hospitalized for influenza-like illness.

While 412 babies comprising 36 percent reported an outpatient visit for a respiratory cause, 555 children representing 48 percent had no flu or flu-like episodes. It was observed that mothers who were vaccinated shared a 41 percent lower risk of laboratory-confirmed influenza virus infection and a 39 percent decreased threat of hospitalization from influenza-like illness. Blood samples of babies born to mothers who were vaccinated apparently revealed elevated levels of flu antibodies at birth and during 2 to 3 months than babies born to unvaccinated women.

The study is published online and will appear in the February 2011 print issue of Archives of Pediatrics and Adolescent Medicine, one of the JAMA/Archives journals.