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Rapid Protective Effects of Early BCG on Neonatal Mortality Among Low Birth Weight Boys: Observations From Randomized
Sofie Biering-Sørensen1,2, Kristoffer Jarlov Jensen1,2,3, Ivan Monterio1
1Projécto de Saúde Bandim, INDEPTH Network, Guinea-Bissau.
Insights
Early Bacille Calmette-Guérin (BCG) vaccination significantly reduces neonatal mortality in boys, particularly within the first week. This BCG vaccine benefit shifts to later weeks for girls, highlighting the importance of timely infant immunization.
Area of Science:
- Immunology
- Neonatal Health
- Public Health
Background:
- Randomized trials demonstrate that the Bacille Calmette-Guérin (BCG) vaccine reduces neonatal mortality in low-weight infants.
- The nonspecific mortality reduction by BCG vaccine is well-documented.
Purpose of the Study:
- To investigate sex-specific differences in the timing of mortality reduction following early BCG vaccination.
- To analyze the impact of BCG on all-cause mortality in neonatal male and female infants.
Main Methods:
- Meta-analysis of data from three randomized controlled trials (RCTs) involving 6583 infants.
- Examination of mortality rate ratios (MRR) for BCG-vaccinated versus control groups, stratified by sex and week of life.
Main Results:
- Boys experienced higher mortality in the first week, with BCG reducing this by threefold (MRR 0.36).
- BCG's protective effect for boys diminished in weeks 2-4 (MRR 0.91).
- Girls showed a limited early effect (MRR 0.85) but a significant reduction in weeks 2-4 (MRR 0.56).
Conclusions:
- Early BCG vaccination provides a critical, immediate survival benefit for male infants, particularly against sepsis.
- The timing of BCG's mortality benefit differs between sexes, underscoring the importance of prompt administration after birth.
Background:
Three randomized trials (RCTs) in low-weight (<2.5 kg) infants have shown that Bacille Calmette-Guérin (BCG) vaccine nonspecifically reduces all-cause mortality in the neonatal period.
Methods:
Using data from 3 RCTs of early BCG (n = 6583) we examined potential sex differences in the timing of the mortality reduction in the neonatal period, presenting metaestimates of the main outcome mortality rate ratios (MRR) for BCG-vaccinated and controls.
Results:
Among controls, boys had a particularly high mortality during the first week after randomization: male-female MRR 2.71 (95% CI, 1.70-4.50). During the first week, BCG had a marked beneficial effect for boys, reducing mortality 3-fold (MRR [BCG/no BCG] = 0.36 [0.20-0.67]). In weeks 2-4 the effect waned for boys (MRR = 0.91 [0.51-1.69]). In girls, the pattern was opposite with a limited effect in the first week (MRR = 0.85 [0.46-1.54]), but a significant reduction in weeks 2-4 (MRR = 0.56 [0.31-1.00]). This was consistent in all 3 trials. Verbal autopsies linked early benefit to fewer sepsis-related deaths among BCG-vaccinated boys.
Discussion:
The marked reduction in mortality in the days after BCG vaccination in boys emphasizes the importance of providing BCG soon after birth.
Trial Registration Numbers:
ClinicalTrials.gov (NCT00146302) and ClinicalTrials.gov (NCT00625482).
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