Becker-Dreps S, et al. - Researchers determined the clinical effectiveness of prenatal tetanus, diphtheria, acellular pertussis (Tdap), and assessed if the effectiveness varies by gestational age at immunization. In this nationwide cohort study of pregnant women with deliveries in 2010–2014 and their infants, they identified Tdap receipt by the pregnant women, and hospitalizations and outpatient visits for pertussis in their infants until the infants reached 18 months of age via analyzing commercial insurance claims data in 2016–2017. Compared with infants of unimmunized mothers, infants of mothers who received prenatal Tdap experienced half the rate of pertussis. Hence, changing the currently recommended timing of Tdap administration in pregnancy is not supported.