Pregnant Mom's Flu Shot Protects Baby

Sept. 17, 2008 -- Pregnant women who get flu shots protect their infants up to age 6 months, a clinical trial shows.

The study, conducted in Bangladesh and led by Mark C. Steinhoff, MD, at Baltimore's Johns Hopkins University, is the first definitive proof that flu vaccines benefit both mother and infant.

"Our study shows that a newborn's risk of infection can be greatly reduced by vaccinating Mom during pregnancy. It's a two-for-one benefit," Steinhoff says in a news release. "Infants under six months have the highest rates of hospitalization from influenza among children in the U.S."

U.S. guidelines advise pregnant women to get flu shots, but only 12% to 13% do. Obstetricians have been slow to pass the recommendation on to women, even though most agree that getting the flu during pregnancy is dangerous.

The study enrolled 340 mothers who had not received a flu shot for at least three years. The study showed that vaccinating pregnant women:

• Cut infants' risk of getting lab-confirmed flu by at least 63%
• Cut both infants' and mothers' risk of respiratory disease with fever by one-third
• Prevented respiratory disease with fever in 14 infants and seven mothers for every 100 women vaccinated
• Prevented one case of lab-confirmed flu for every 16 women vaccinated

A number of factors affected the study, including a shortage of flu tests. But analysis of these factors suggested that, if anything, they led to an underestimation of the true benefit of flu shots for pregnant women.

Infants under age 6 months cannot get a flu shot. And since it takes two shots for full protection, there's a gap during which a child might be vulnerable to the flu.

"Pregnant women should be encouraged to be vaccinated for the flu to protect their infants and themselves," Steinhoff says.

Researchers from the International Center for Diarrheal Disease Research in Dhaka, Bangladesh, and from Emory University in Atlanta also contributed to the study. The study appears in the Sept. 17 Online First issue of TheNew England Journal of Medicine.