COVID - Transmission and Morbidity in Malawi (COVID-TMM)

Early in the COVID-19 pandemic, sub-Saharan Africa was expected to experience devastating morbidity and mortality from SARS-CoV-2. Instead, most countries in the region, including Malawi, reported rates far lower than those seen in Europe and the Americas. This study seeks to understand the biological and immunological factors underlying this unexpected pattern, with a focus on how population-level immune characteristics influence susceptibility to infection, disease severity, transmission, and vaccine responses.

The investigators hypothesize that widespread exposure to malaria and intestinal паразitic infections may shape innate immune responses in ways that reduce the risk of symptomatic COVID-19, potentially through enhanced or tolerogenic immune mechanisms. At the same time, these infections—along with chronic or mild undernutrition, anemia, and micronutrient deficiencies—may impair the acquisition and durability of antibody and cellular immune responses following SARS-CoV-2 infection or vaccination, increasing vulnerability to reinfection or vaccine breakthrough infections.

To test these hypotheses, the study will enroll up to 200 symptomatic SARS-CoV-2 index cases in Malawi, approximately 700 household contacts, and up to 600 vaccinated individuals. Researchers will characterize innate immune phenotypes that distinguish uninfected Malawians from Western controls and assess whether these immune profiles protect against infection or progression to severe disease. Participants who are infected or vaccinated will be followed for up to 18 months to evaluate the development and longevity of antibody responses, memory B cells, and other adaptive immune responses.

Overall, the study aims to clarify how infectious exposures and nutritional factors interact with innate and adaptive immunity to shape COVID-19 outcomes and vaccine effectiveness in sub-Saharan African populations.