High SARS-CoV-2 seroprevalence in Lagos, Nigeria with robust antibody and cellular responses

Background Early evidence suggested that the impact of the COVID-19 pandemic was less severe in Africa compared to other parts of the world. However, more recent studies indicate higher SARS-CoV-2 infection and COVID-19 mortality rates on the continent than previously documented. Research is needed to better understand SARS-CoV-2 seroprevalence and immunity in Africa. Methods Our collaboration with the Lagos State COVID-19 Taskforce, enabled secondary analyses of immune responses in healthcare workers (HCWs) and Oxford/AstraZeneca COVID-19 vaccine recipients from the general population across 5 local government areas (LGAs) in Lagos State, Nigeria. Western blots were used to simultaneously detect SARS-CoV-2 spike and nucleocapsid (N) antibodies and stimulation of peripheral blood mononuclear cells with N followed by an IFN-{gamma} ELISA was used to examine T cell responses. Findings Antibody data demonstrated high SARS-CoV-2 seroprevalence of 71.6% (96/134) in HCWs and 54.8% (63/115) in the general population. Antibodies directed to only SARS-CoV-2 N, suggesting pre-existing coronavirus immunity, were seen in 10.4% (14/134) of HCWs and 20.0% (23/115) of the general population. T cell data showed that IFN-{gamma} responses against SARS-CoV-2 N were robust in detecting exposure to the virus, demonstrating 87.5% sensitivity and 92.3% specificity. Interpretation These results have important implications for understanding the paradoxical high SARS-CoV-2 infection with low mortality rate in Africa as compared to other parts of the world, as well as for the development of T cell-based diagnostics and vaccines.