Safety of influenza vaccination during pregnancy.
The purpose of this study was to evaluate the safety of influenza vaccine that is administered in the second or third trimester of gestation. A retrospective electronic database search of 5 influenza seasons (July 1, 1998, to June 30, 2003) was performed at a large multispecialty clinic in Houston, Texas. Immunization rates were calculated, and outcomes of pregnancy were compared between a cohort of healthy women who received influenza vaccine and a control group of healthy unvaccinated women who were matched by age, month of delivery, and type of medical insurance. Among 7183 eligible mother-infant pairs, only 252 pregnant women (3.5%) received the influenza vaccine. Women with medical insurance were more likely to be vaccinated, although the rates for women with chronic underlying conditions were similar to those of healthy women, regardless of insurance status. The mean gestational age at the time of influenza vaccination was 26.1 weeks (range, 14-39 weeks). No serious adverse events occurred within 42 days of vaccination, and there was no difference between the groups in the outcomes of pregnancy (including cesarean delivery and premature delivery) and infant medical conditions from birth to 6 months of age. Influenza vaccine that was administered in the second or third trimester of gestation was safe in this study population.