Background: To determine the non-specific effects of diphtheria, tetanus and pertussis (DTP) vaccination and sex on mortality before 30 months of age among those who received Bacille Calmette Guerin (BCG) vaccine in a high mortality area.
Methods: This analysis used a longitudinal study of child survival monitoring the use of primary care services, morbidity and mortality in Metro Cebu, The Philippines. Participants included 14 537 children under 30 months of age who received a BCG vaccination from July 1988 to January 1991. The main outcome measure was all-cause mortality.
Results: Mortality before 30 months of age was 57% lower among BCG-vaccinated children who received DTP vaccination than BCG-vaccinated children who did not receive DTP vaccination {hazard ratio (HR) for vaccinated vs unvaccinated 0.43 [95% confidence interval (CI) 0.21-0.88]}. Females had lower mortality rates [HR = 0.19 (0.04-0.86), P = 0.03] than males among DTP-unvaccinated children. The protective effect of DTP vaccination was more pronounced in males [HR 0.32 (0.14-0.73)] than in females [HR 0.86 (0.18-4.23)]. DTP vaccination increased (interaction term P = 0.08) the female-to-male mortality ratio to 0.76 (0.52-1.12).
Conclusions: Among BCG-vaccinated children under 30 months of age, DTP vaccination is associated with improved survival. The increased female-male mortality ratio is associated with reduced mortality among males following DTP vaccination rather than increased mortality among female children.