Under-reporting of COVID-19 and the limited information about circulating SARS-CoV-2 variants remain major challenges for many African countries. We analyzed SARS-CoV-2 infection dynamics in Addis Ababa and Jimma, Ethiopia, focusing on reinfection, immunity, and vaccination effects. We conducted an antibody serology study spanning August 2020 to July 2022 with five rounds of data collection across a population of 4723, sequenced PCR-test positive samples, used available test positivity rates, and constructed two mathematical models integrating this data. A multivariant model explores variant dynamics identifying wildtype, alpha, delta, and omicron BA.4/5 as key variants in the study population, and cross-immunity between variants, revealing risk reductions between 24% and 69%. An antibody-level model predicts slow decay leading to sustained high antibody levels. Retrospectively, increased early vaccination might have substantially reduced infections during the delta and omicron waves in the considered group of individuals, though further vaccination now seems less impactful.
GrantsAddis Ababa Health Bureau Bavarian State Ministry of Sciences, Research and the Arts (Bayerisches Staatsministerium) Bundesministerium fr Bildung und Forschung (Federal Ministry of Education and Research) EU Volkswagenstiftung Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) University of Bonn - Free State of Bavaria Jimma Medical Center, Oromia Regional Health Bureau Germany Ministry of Education and Research