By November 2021, after the third wave of severe acute respiratory syndrome coronavirus 2 infections in South Africa, seroprevalence was 60% in a rural community and 70% in an urban community. High seroprevalence before the Omicron variant emerged may have contributed to reduced illness severity observed in the fourth wave.
Keywords: COVID-19; SARS-CoV-2; case-to-infection ratio; coronavirus disease; fatality-to-infection ratio; hospitalization-to-infection ratio; respiratory infections; seroprevalence; severe acute respiratory syndrome coronavirus 2; vaccine-preventable diseases; viruses; zoonoses.