SARS-CoV-2 seropositivity amongst healthcare workers in South Africa during the Omicron wave: natural infection versus vaccination

Aims Concerns over population-level immunity have been heightened with each successive wave of COVID-19, prompting questions about whether it is primarily derived from vaccination efforts or from previous natural infections with the virus. We wished to determine the seroprevalence of SARS-CoV-2 antibodies among healthcare workers (HCWs) in Pretoria (Tshwane), South Africa, and to establish whether they were derived from vaccination or natural infection.Methods Serum samples were collected from HCWs during the fourth wave of COVID-19 between 1 December 2021 and 13 March 2022. The samples were tested using the Abbott SARS-CoV-2 Spike IgG (S-IgG), IgM (S-IgM) and the SARS-CoV-2 Nucleocapsid IgG (NC-IgG) kits.Results Of the 221 participants, 76% (n=168) were women and 24% (n=53) were men. A total of 96.4% (n=213) of the participants were vaccinated. Natural infection-derived antibodies were detected in 23% (n=51) of participants, and vaccine-derived antibodies in 74% (n=164) of the HCWs.Conclusions Even after three waves of COVID-19, HCWs derived most of their detectable antibodies from vaccination. Vaccination remains an essential tool to protect HCWs and patients from SARS-CoV-2 infection.