Infants born to mothers who received the influenza (flu) vaccine while pregnant are nearly 50% less likely to be hospitalised for the flu than infants born to mothers who did not receive the vaccine while pregnant, according to a new collaborative study by researchers at Wake Forest Baptist Medical Centre and colleagues.
The Advisory Committee on Immunisation Practices (ACIP) recommends influenza vaccination for anyone older than six months, but specifically singles out target groups, including pregnant women, who have a greater risk of influenza-related complications.
"It is recommended that all pregnant women receive the influenza vaccine during pregnancy because it is known that pregnant women have increased morbidity and mortality during pregnancy and in the immediate postpartum period if they get the flu," said Katherine A. Poehling, M.D., MPH., an associate professor of paediatrics and lead author on the study. "We also know that mothers pass antibodies through the placenta to the baby. This study showed us that receiving the influenza vaccine during pregnancy not only protects the mother, but also protects the baby in the early months of life."
The study, which is the first population-based, laboratory-confirmed study to demonstrate this benefit, appears in the American Journal of Obstetrics & Gynecology.
Infants at high risk
Infants less than six months of age have the highest rates of flu hospitalisation among all children, Poehling explained, yet the influenza vaccine is not licensed for or effective in infants that young.
So Poehling and colleagues sought to assess whether receiving the vaccine during pregnancy would provide some protection for the newborn baby.
The researchers analysed data collected by the Centres for Disease Control and Prevention-funded New Vaccine Surveillance Network over the course of seven flu seasons between 2002 and 2009, before the H1N1 pandemic. The data included information about 1,510 babies who had been hospitalised with fever, respiratory symptoms, or both within the first six months of life and had undergone laboratory testing for influenza infection.
Risk almost cut in half
The investigators found that infants born to mothers who received the influenza vaccine during pregnancy were 45% to 48% less likely to be hospitalised with laboratory-confirmed influenza.
"Similar findings have been published from other studies, but they've been published in general journals or journals about paediatrics and infectious diseases," Poehling said. "Where the information is published really does make a difference because paediatricians need to know about it, but it's even more important that the doctors taking care of pregnant women – obstetricians and gynaecologists (OB/GYNs) – know it, too. Paediatricians have been vaccinating children for a long time, but vaccine recommendations for OB/GYNs have changed over the last decade, so everyone is having to learn new recommendations and adjust. This is a relatively new activity for OB/GYNs." - (EurekAlert!, June 2011)