Mortality Risk Among Frail Neonates and Maternal BCG Vaccine Scar Status: Observational Study From Guinea-Bissau

Mortality rates by 6 weeks of age tended to be reduced among neonates born to mothers who had a BCG vaccine scar, compared with those born to mothers with no BCG scar. Background Maternal priming with the Bacille Calmette-Guerin (BCG) vaccine has been associated with reduced offspring mortality rates. We investigated this association in a cohort of frail neonates. Methods We performed an observational study within a randomized BCG trial conducted at the neonatal intensive care unit (NICU) in Guinea-Bissau from 2015 to 2017. At NICU admission and after informed consent, the maternal scar status was evaluated by visual inspection before neonates were randomized 1:1 to receive BCG + oral polio vaccine immediately or at hospital discharge. Stratified by maternal scar status, we assessed overall in-hospital and postdischarge mortality rates through 42 days of age in Cox proportional hazards models providing adjusted mortality rate ratios (aMRRs). Results Overall, 62% of mothers (903 of 1451) had a BCG vaccine scar. During NICU admission, the mortality risk was 1.7% (15 of 903) for neonates born to mothers with a scar versus 3.3% (18 of 548) for those born to mothers with no scar; the aMRR for maternal scar versus no scar was 0.53 (95% CI, .26-1.05), 0.39 (95% CI, .13-1.05) for unvaccinated and 0.70 (95% CI, .26-1.87) for vaccinated neonates. Conclusions This small study indicates that maternal BCG vaccine might be associated with reduced all-cause NICU mortality rate. If confirmed elsewhere, this finding would have substantial ramifications for global health.