BACKGROUND: Maternal priming with the Bacille Calmette-Guérin (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.

Original languageEnglish
JournalThe Journal of Infectious Diseases
Issue number11
Pages (from-to)1237-1244
Publication statusPublished - 1. Jun 2023


  • Bacille Calmette-Guerin (BCG) vaccine
  • NICU mortality
  • maternal BCG priming
  • maternal BCG scar
  • nonspecific effects of vaccines
  • perinatal mortality
  • vertical priming


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