High SARS-CoV-2 Seroprevalence in Lagos, Nigeria with Robust Antibody and Cellular Immune 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 infection and immunity in Africa. Methods: In early 2021, we studied the immune responses in healthcare workers (HCWs) at Lagos University Teaching Hospital ( n = 134) and Oxford-AstraZeneca COVID-19 vaccine recipients from the general population ( n = 116) across five local government areas (LGAs) in Lagos State, Nigeria. Western blots were used to simultaneously detect SARS-CoV-2 spike and nucleocapsid (N) antibodies ( n = 250), and stimulation of peripheral blood mononuclear cells with N followed by an IFN-������ ELISA was used to examine T cell responses ( n = 114). Results: Antibody data demonstrated high SARS-CoV-2 seroprevalence of 72 & BULL;4% (97/134) in HCWs and 60 & BULL;3% (70/116) in the general population. Antibodies directed to only SARS-CoV-2 N, suggesting pre-existing coronavirus immunity, were seen in 9 & BULL;7% (13/134) of HCWs and 15 & BULL;5% (18/116) of the general population. T cell responses against SARS-CoV-2 N ( n = 114) were robust in detecting exposure to the virus, demonstrating 87 & BULL;5% sensitivity and 92 & BULL;9% specificity in a subset of control samples tested. T cell responses against SARS-CoV-2 N were also observed in 83.3% of individuals with N-only antibodies, further suggesting that prior non-SARS-CoV2 coronavirus infection may provide cellular immunity to SARS-CoV-2. Conclusions: These results have important implications for understanding the paradoxically high SARS-CoV-2 infection with low mortality rate in Africa and supports the need to better understand the implications of SARSCoV-2 cellular immunity.