Estimates of case-fatality ratios of measles in low-income and middle-income countries: a systematic review and modelling analysis

Background In the 21st century, increases in immunisation coverage and decreases in under-5 mortality have substantially reduced the global burden of measles mortality. However, the assessment of measles mortality burden is highly dependent on estimates of case-fatality ratios for measles, which can vary according to geography, health systems infrastructure, prevalence of underlying risk factors, and measles endemicity. With imprecise case-fatality ratios, there is continued uncertainty about the burden of measles mortality and the effect of measles vaccination. In this study, we aimed to update the estimations of case-fatality ratios for measles, to develop a prediction model to estimate case-fatality ratios across heterogeneous groupings, and to project future case-fatality ratios for measles up to 2030. Methods We did a review of the literature to identify studies examining measles cases and deaths in low-income and middle-income countries in all age groups from 1980 to 2016. We extracted data on case-fatality ratios for measles overall and by age, where possible. We developed and examined several types of generalised linear models and determined the best-fit model according to the Akaike information criterion. We then selected a best-fit model to estimate measles case-fatality ratios from 1990 to 2015 and projected future case-fatality ratios for measles up to 2030. Findings We selected 124 peer-reviewed journal articles published between Jan 1,1980, and Dec 31,2016, for inclusion in the final review-85 community-based studies and 39 hospital-based studies. We selected a log-linear prediction model, resulting in a mean case-fatality ratio of 2.2% (95% CI 0.7-4.5) in 1990-2015. In community-based settings, the mean case-fatality ratio was 1.5% (0.5-3.1) compared with 2.9% (0.9-6.0) in hospital-based settings. The mean projected case-fatality ratio in 2016-2030 was 1.3% (0.4-3.7). Interpretation Case-fatality ratios for measles have seen substantial declines since the 1990s. Our study provides an updated estimation of case-fatality ratios that could help to refine assessment of the effect on mortality of measles control and elimination programmes. Copyright 2019 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.