Prospective cohort study to evaluate Lassa fever incidence, Lassa fever symptoms, and co-infection with malaria in West Africa

Since the isolation of the Lassa mammarenavirus (LASV) in 1969, the disease has continued to cause seasonal morbidity and mortality. 300'000 annual infections are estimated in West Africa, making LASV a primary cause of haemorrhagic fever worldwide. A crucial step to assess the feasibility and prepare for potential future Lassa vaccine efficacy trials is to gather epidemiological data on the background rates of infection and disease due to LASV in endemic areas, because incidence & spatial distribution of Lassa Fever (LF) is likely to be significantly underestimated based on existing data, due to gaps in diagnostics, surveillance and access to health services. The aim of this project, "Prospective Multi-site cohort study to estimate the incidence of infection and disease due to Lassa Fever Virus in westafrican countries", is to conduct epidemiological cohort study that will assess LF disease and LASV incidence to determine the feasibility of future Phase IIb or III clinical trials for assessing the efficacy of LF vaccine or therapeutic candidates. Strategic aims are to

1. provide information on prevalence and incidence and to inform the design of future studies,
2. Identify sites, 
3. Assess and strengthen the site and investigator capability and capacity.

Objective

For each Lassa-endemic country participating in the study, separately :

1. to assess the incidence rate of symptomatic confirmed LF ;
2. to estimate the incidence rate of LASV infection.

This study aims to assess the incidence of Lassa fever (LF) disease and Lassa virus (LASV) infection, including when stratified by site, age, sex, and most recent previous LASV serostatus, and to differentiate LF from malaria symptomology. Addressing these emergent knowledge gaps will inform the design and feasibility of future late-stage clinical trials for assessing the efficacy, immunogenicity, and/or safety of LF vaccine candidates. This study will further strengthen site and investigator capability and capacity, building on existing capacity sustained throughout the initial ENABLE Lassa Research programme from 2020 to 2024, to facilitate the conduct of future clinical trials.