SARS-CoV-2 Seroprevalence after Third Wave of Infections, South Africa

Abstract

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.

Figure

Severe acute respiratory syndrome coronavirus 2 seroprevalence at each blood collection, by age group, in a rural community (A) and urban community (B), South Africa, March 2020–November 2021. Baseline blood draw (BD1) collected July 20–September 17, 2020; second draw (BD2), September 21 – October 10, 2020; third draw (BD3), November 23–December 12, 2020; fourth draw (BD4), January 25–February 20, 2021; fifth draw (BD5), March 22–April 11, 2021; sixth draw (BD6), May 20–June 9, 2021; seventh draw (BD7), July 19–August 5, 2021; eighth draw (BD8), September 13–25, 2021; ninth draw (BD9), November 15–27, 2021. Error bars represent 95% credible intervals. Seroprevalence estimates adjusted for sensitivity and specificity of assay.