Population-level risk factors related to measles case fatality: a conceptual framework based on expert consultation and literature review

Abstract

AbstractIntroductionA better understanding of population-level factors related to measles case fatality is needed to estimate measles mortality burden and impact of interventions such as vaccination. This study aimed to develop a conceptual framework of mechanisms associated with measles case fatality ratios (CFRs) and assess the scope of evidence available for related indicators in the published literature.MethodsUsing expert consultation, we developed a conceptual framework of mechanisms associated with measles CFR and identified population-level indicators potentially associated with each mechanism. We then conducted a literature review by searching PubMed on October 31, 2021 to determine and classify the scope of evidence for the indicators identified by expert consultation. Studies were included if they contained evidence of an association between an indicator and measles CFR and were excluded if they were from non-human studies or reported non-original data.ResultsExpert consultation identified five mechanisms in a conceptual framework of factors related to measles CFR: health system access and care-seeking behaviors, health system quality, measles control and epidemiology, nutritional status, and risk of secondary infection. Thirty-seven measurable population-level indicators were identified by expert consultation as proxies for the mechanisms. We identified 3772 studies for review and found 49 studies showing at least one significant association with CFR for 15 indicators and only non-significant associations for 5 indicators. Inadequate data were available to evaluate the remaining 17 indicators. A randomized controlled trial provided evidence for a relationship between vitamin A treatment and measles CFR. Average household size, educational attainment, first-dose coverage of measles-containing vaccine, human immunodeficiency virus prevalence, second-dose coverage of measles-containing vaccine, stunting prevalence, surrounding conflict, travel time to major city or settlement, travel time to nearest health care facility, under-five mortality rate, underweight prevalence, vitamin A deficiency prevalence, and wasting prevalence had quantitative observational level evidence. Level of health care available had qualitative evidence of a relationship with measles CFR.ConclusionTo reduce uncertainty in measles CFR estimation, population-level factors representative of underlying mechanisms associated with CFR could be used. Our study used expert consultation and literature review to provide additional insights and a summary of the available evidence of these underlying mechanisms and indicators that could inform future estimations of measles CFR.