Pertussis Risk Significantly Lessened With Prenatal Tdap

Prenatal tetanus, diphtheria, acellular pertussis (Tdap) immunization is associated with a significantly reduced rate of pertussis in infants compared with children of unimmunized mothers, according to the results of a recent study.

In order to explore the clinical effectiveness of prenatal Tdap and how the effectiveness varies by gestational age at immunization, researchers conducted a nationwide cohort study of pregnant women who delivered in 2010-2014 and their infants. Insurance claims data were used to identify Tdap recipients and hospitalizations and outpatient visits for pertussis were analyzed in infants until 18 months of age.

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Overall, 675,167 mother-infant pairs were included in the cohort. Among children of mothers who received prenatal Tdap, the rate of pertussis was 43% lower (hazard ratio [HR] 0.57) compared with infants whose mothers did not receive the vaccine either prenatally or postpartum.

Rates were lower among infants whose mothers were vaccinated during the third trimester, while those whose mothers received Tdap at <27 weeks of gestation did not experience reductions.

“Infants of mothers who received prenatal Tdap experienced half the rate of pertussis as compared with infants of unimmunized mothers. These results do not provide evidence to support changing the currently recommended timing of Tdap administration in pregnancy,” the researchers concluded.

—Michael Potts

Reference:

Becker-Dreps S, Butler AM, McGrath LJ, et al. Effectiveness of prenatal tetanus, diphtheria, acellular pertussis vaccination in the prevention of infant pertussis in the U.S. [published online June 11, 2018]. Am J Prev Med. doi: 10.1016/j.amepre.2018.04.013.