Romanin V, Acosta AM, del Valle Juarez M, et al. - Given that in Argentina, in response to experiencing its highest pertussis incidence and mortality rates of the last decade (60% of deaths were among infants aged < 2 months), a dose of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine was recommended for all pregnant women at ≥ 20 weeks of gestation, researchers investigated the effectiveness of maternal Tdap vaccination in preventing pertussis among infants aged < 2 months in Argentina in this matched case-control evaluation. From September 2012 to March 2016, they included 71 pertussis cases from 6 hospital sites and 300 controls in the analysis. Vaccination during pregnancy was reported among mothers of 49% of case-patients and 78% of controls. Findings support the efficacy of Tdap vaccination during pregnancy in preventing pertussis in infants aged < 2 months in Argentina; a similar effect was observed when administered during the second or third trimester of pregnancy.