HONOLULU — When women are given influenza vaccine in their third trimester of pregnancy, their infants receive protection against flu infection, results of a randomized controlled trial of more than 300 pregnant women confirm.
“This is the first randomized controlled trial of maternal immunization with influenza vaccine,” Dr. Mark C. Steinhoff reported at the annual meeting of the Pediatric Academic Societies.
The study was part of the Maternal Gift Study, which involved 340 pregnant women and 331 live births in a middle-class urban population in Bangladesh. Women in the study were randomized to receive either influenza vaccine or pneumococcal conjugate vaccine during their third trimester of pregnancy. For the purposes of this analysis, the investigators used the mother-infant pairs receiving pneumococcal vaccine as the control group (MMWR 2006;55[No. RR-10]:11-12).
The mothers were an average 25 years old, and were vaccinated an average 55 days before giving birth. Ninety-two percent gave birth in a hospital or clinic, 46% by cesarean delivery. The infants averaged just above 3 kg at birth and were breast-fed exclusively an average of 14 weeks.
The trivalent influenza vaccine was associated with a 63% reduction in proven influenza in infants 0-6 months of age and a 30% reduction in all febrile respiratory illnesses in infants and their mothers.
The fact that the influenza vaccine was compared with the pneumococcal vaccine and not with placebo probably resulted in an underestimate of the influenza vaccine's effectiveness, said Dr. Steinhoff of Johns Hopkins University, Baltimore.
Dr. Steinhoff disclosed that he has served on Sanofi's speakers bureau and has received research support from Sanofi-Aventis, Wyeth, and Merck & Co.