Quantifying child mortality reductions related to measles vaccination

Abstract

Background: This study characterizes the historical relationship between coverage of measles containing vaccines (MCV) and mortality in children under 5 years, with a view toward ongoing global efforts to reduce child mortality.

Methodology/principal findings: Using country-level, longitudinal panel data, from 44 countries over the period 1960-2005, we analyzed the relationship between MCV coverage and measles mortality with (1) logistic regressions for no measles deaths in a country-year, and (2) linear regressions for the logarithm of the measles death rate. All regressions allowed a flexible, non-linear relationship between coverage and mortality. Covariates included birth rate, death rates from other causes, percent living in urban areas, population density, per-capita GDP, use of the two-dose MCV, year, and mortality coding system. Regressions used lagged covariates, country fixed effects, and robust standard errors clustered by country. The likelihood of no measles deaths increased nonlinearly with higher MCV coverage (ORs: 13.8 [1.6-122.7] for 80-89% to 40.7 [3.2-517.6] for ≥95%), compared to pre-vaccination risk levels. Measles death rates declined nonlinearly with higher MCV coverage, with benefits accruing more slowly above 90% coverage. Compared to no coverage, predicted average reductions in death rates were -79% at 70% coverage, -93% at 90%, and -95% at 95%.

Conclusions/significance: 40 years of experience with MCV vaccination suggests that extremely high levels of vaccination coverage are needed to produce sharp reductions in measles deaths. Achieving sustainable benefits likely requires a combination of extended vaccine programs and supplementary vaccine efforts.

Figure 1. Estimated changes in measles-specific mortality rates for children under 5 years old with increasing MCV coverage.

Shown in the graph is the percentage change in measles-specific mortality rates in children under 5 years associated with increasing MCV coverage to 90% (Panel A), 95% (Panel B), and 99% (Panel C) from different starting MCV coverage levels (solid colored bars – interquartile ranges; black vertical lines – 5th to 95th percentile ranges).