Estimating the health impact of vaccination against ten pathogens in 98 low-income and middle-income countries from 2000 to 2030: a modelling study

Abstract

Background: The past two decades have seen expansion of childhood vaccination programmes in low-income and middle-income countries (LMICs). We quantify the health impact of these programmes by estimating the deaths and disability-adjusted life-years (DALYs) averted by vaccination against ten pathogens in 98 LMICs between 2000 and 2030.

Methods: 16 independent research groups provided model-based disease burden estimates under a range of vaccination coverage scenarios for ten pathogens: hepatitis B virus, Haemophilus influenzae type B, human papillomavirus, Japanese encephalitis, measles, Neisseria meningitidis serogroup A, Streptococcus pneumoniae, rotavirus, rubella, and yellow fever. Using standardised demographic data and vaccine coverage, the impact of vaccination programmes was determined by comparing model estimates from a no-vaccination counterfactual scenario with those from a reported and projected vaccination scenario. We present deaths and DALYs averted between 2000 and 2030 by calendar year and by annual birth cohort.

Findings: We estimate that vaccination of the ten selected pathogens will have averted 69 million (95% credible interval 52-88) deaths between 2000 and 2030, of which 37 million (30-48) were averted between 2000 and 2019. From 2000 to 2019, this represents a 45% (36-58) reduction in deaths compared with the counterfactual scenario of no vaccination. Most of this impact is concentrated in a reduction in mortality among children younger than 5 years (57% reduction [52-66]), most notably from measles. Over the lifetime of birth cohorts born between 2000 and 2030, we predict that 120 million (93-150) deaths will be averted by vaccination, of which 58 million (39-76) are due to measles vaccination and 38 million (25-52) are due to hepatitis B vaccination. We estimate that increases in vaccine coverage and introductions of additional vaccines will result in a 72% (59-81) reduction in lifetime mortality in the 2019 birth cohort.

Interpretation: Increases in vaccine coverage and the introduction of new vaccines into LMICs have had a major impact in reducing mortality. These public health gains are predicted to increase in coming decades if progress in increasing coverage is sustained.

Funding: Gavi, the Vaccine Alliance and the Bill & Melinda Gates Foundation.

Figure 1

Vaccine coverage across the ten pathogens considered Vaccine coverage, calculated as the mean number of vaccines received per child born in a specific year, is shown for 2000 (A), 2010 (B), and 2019 (C). The colour scale shows the expected number of vaccines received per child in each country. (D) Routine vaccine coverage for each pathogen, from 2000 to 2019, averaged across all 98 countries, except for Japanese encephalitis, Neisseria meningitidis serogroup A, and yellow fever, which were averaged across the 16, 26, and 32 endemic countries for those pathogens, respectively. The average was obtained by dividing total vaccine doses by the total eligible population. PCV=pneumococcal conjugate vaccine.

Figure 2

Estimates of disease-specific deaths by calendar year, from 2000 to 2030, across 98 countries, for reported and projected vaccine coverage and counterfactual (no vaccination) coverage Lines show estimates of deaths for the two scenarios, for all ages. The corresponding shaded areas show the 95% credible intervals (2·5% and 97·5% quantiles). The grey shaded parts show the area where the 95% credible intervals for the two scenarios overlap. PCV=pneumococcal conjugate vaccine.

Figure 3

Estimates of deaths averted by vaccination in 98 countries (A) Estimates of death averted by calendar year (summing across all ages) and pathogen. (B) Estimates of deaths averted by year of birth (summing across lifetime) and pathogen. (C) Proportion of lifetime deaths due to the ten pathogens considered in the no-vaccination counterfactual scenario that are predicted to be averted by vaccination, by country, across 2000–19 birth cohorts. PCV=pneumococcal conjugate vaccine.