A scoping review on the associations and potential pathways between malnutrition and measles

Amid a measles resurgence worldwide, many affected regions also find themselves in circumstances of conflict, humanitarian or political crises, climate extremes, ongoing pandemic challenges, income inequality and economic downturns. Those contextual factors have driven increases in worldwide undernourishment over the past year. The overlap and frequent occurrence of those socio-structural determinants in fragile geographies is worrying as a synergistic relationship between measles and malnutrition has been reported. A scoping review was conducted to map current evidence and identify research gaps on the association between malnutrition and measles. Sixty-seven studies were retained following a search of multiple databases, snowballing and consultations with experts. Studies reported on a measure of association, a relationship, or potential mechanisms behind the link between malnutrition and measles. Overall, there was evidence of a positive correlation between undernutrition and reported measles incidence and mortality. All studies reviewed found an association between vitamin A deficiency and increased likelihood of incident measles, measles-related complications and measles-related deaths. Available evidence also suggested that therapeutic vitamin A can significantly reduce the odds of measles-related mortality, and preventative vitamin A can reduce reported measles incidence. Little data shed light on potential pathways behind malnutrition and measles. Inconsistent variable definitions (i.e. malnutrition and measles cases) across studies precluded calculating a cumulative effect size, and findings may be impacted by uncontrolled confounding factors. This scoping review reinforces the hypothesis of a synergistic relationship between measles and malnutrition and highlights the need for an integrated approach to the delivery of malnutrition interventions and measles prevention and control. In addition, further robust studies are needed to better define pathophysiological targets for interventions and allow for stronger inferences to policy making. Future research should also consider using a standardized approach to defining malnutrition and measles to ensure comparability of outcomes across studies. ### Competing Interest Statement ICTT had a remunerated internship with the Early Childhood Nutrition Unit of the United Nations Children's Fund (UNICEF) to initiate this study, and a research contract with the World Health Organization (WHO) to complete and publish it. CG and AI contributed to the design of the study and its overarching goals, and to the research and analysis methodology. CG, POC and AI contributed to the review of the manuscript. ### Funding Statement This scoping review was initiated as part of a remunerated internship with the Early Childhood Nutrition Unit of the United Nations Children's Fund (UNICEF) and was completed within a research contract funded by the World Health Organization (WHO). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present work are contained in the manuscript.