Is early measles vaccination associated with stronger survival benefits than later measles vaccination?”

Description

Abstract:

Background. A recent WHO review concluded that there is evidence of beneficial non-specific effects of measles vaccine (MV), the vaccine reducing mortality by more than can be explained by preventing measles infections. Previous studies have suggested that early MV is more beneficial than late MV. We tested whether early MV before 9 months of age is associated with lower mortality than MV given after 9 months of age.
Methods. Bandim Health Project follows children under 5 years of age through a Health and Demographic Surveillance System with biannual visits in rural Guinea-Bissau. The present study included children from 6 to 36 months of age, who had their vaccination card inspected between January 1st 1999 and May 15th 2006. We examined their mortality until the next time their vaccination card could be inspected or for a maximum of 6 months. Mortality rates were compared in Cox proportional-hazards models with age as underlying time, providing mortality rate ratios (MRR) for measles-vaccinated versus measles-unvaccinated children overall and by age at vaccination.
Results. Among the 14,815 children (31,730 observations), 70% had received MV and 30% had not. MV was associated with better survival compared with being measles unvaccinated: MRR: 0.76 (95% CI: 0.63-0.91). Children vaccinated before 9 months of age had a MRR of 0.68 (0.53-0.87), MV between 9 and 11 months was associated with a MRR of 0.77 (0.62-0.96) and for MV after 12 months the MRR was 0.86 (0.67-1.11). The beneficial effect of age at vaccination was stronger and significant for girls but not for boys. Censoring the deaths caused by measles infection did not alter the conclusions.
Conclusion. MV is associated with a lower mortality. MV before 9 months of age was associated with a larger survival advantage for girls.