Effectiveness of prenatal versus postpartum Tdap vaccination in preventing infant pertussis.

Most severe and fatal cases of pertussis occur in infants <8 weeks of age, before initiation of the primary pertussis vaccine series. Women are recommended to receive Tdap vaccine at the start of the third trimester of each pregnancy to optimize transplacental transfer of antibodies to the fetus. This recommendation was made by the Advisory Committee for Immunization Practices based on immunogenicity data, and no studies in the United States have yet evaluated the effectiveness of this strategy in reducing pertussis incidence in infants.
 We evaluated a cohort of mothers with documented Tdap vaccination histories in the California Immunization Registry (CAIR) to determine if infants whose mothers received Tdap vaccine between 27 and 36 weeks gestation had a lower risk of pertussis <8 weeks of age compared to infants born to women who received Tdap vaccine within 14 days postpartum.
 Tdap vaccination received during 27-36 weeks gestation was found to be 85% (95% CI: 33%-98%) more effective at preventing pertussis in infants <8 weeks of age compared to Tdap vaccination postpartum. Vaccination received between 27-36 weeks gestation was more effective at preventing pertussis in infant than vaccination received during the second trimester.
 Tdap vaccination during 27-36 weeks gestation was 85% more effective than postpartum vaccination at preventing pertussis in infants <8 weeks of age. Efforts should be made by prenatal care providers to provide Tdap vaccine to pregnant women during routine prenatal visits at the earliest opportunity between 27-36 weeks gestation.

Authors:Winter K1, Nickell S2, Powell M2, Harriman K2.
Journal:Clin Infect Dis. 2016