Investigating cross-reactive antibodies to SARS-CoV-2 in pre-pandemic African samples

The SARS-CoV-2 pandemic had a profound global impact, yet Africa exhibited significantly lower infection and mortality rates compared to other continents. This study explores the hypothesis that pre-existing immunity may have contributed to this phenomenon. While factors like demographics, lifestyle, and climate have been previously discussed, the potential role of crossreactive immunity remains underexplored. We examined pre-pandemic sera collected in 2019 and 2003 from populations in Zimbabwe to assess levels of IgG and IgM antibodies that might crossreact with SARS-CoV-2, particularly those targeting the spike protein. Using Rapid Detection Tests (RDT) and ELISA assays, we investigated the prevalence and levels of these antibodies, hypothesizing that prior exposure to other human coronaviruses or pathogens, may have provided cross-protection against SARS-CoV-2. Our findings shed light on the immunological landscape in Zimbabwe prior to the COVID-19 pandemic, contributing valuable insights into the possible epidemiological factors that shaped Africa's response to the virus.