Estimation of vaccine effectiveness against SARS-CoV-2-associated hospitalization using sentinel surveillance in South Africa

• Published in: International journal of epidemiology 2024-08, Vol.53 (5)
• Main Authors: Chiwandire, Nicola, Walaza, Sibongile, von Gottberg, Anne, Wolter, Nicole, Du Plessis, Mignon, Moosa, Fahima, Groome, Michelle J, Nel, Jeremy, Variava, Ebrahim, Dawood, Halima, Makhasi, Mvuyo, Feldstein, Leora R, Marcenac, Perrine, Lafond, Kathryn E, Samuels, Aaron M, Cohen, Cheryl
• Format: Article
• Language: English
• Subjects: Ad26COVS1; Adolescent; Adult; Aged; BNT162 Vaccine; Case-Control Studies; COVID-19 - epidemiology; COVID-19 - prevention & control; COVID-19 Vaccines - immunology; Female; Hospitalization - statistics & numerical data; Humans; Male; Middle Aged; Original; SARS-CoV-2 - immunology; Sentinel Surveillance; South Africa - epidemiology; Vaccine Efficacy; Young Adult
• ISSN: 1464-3685; 0300-5771; 1464-3685
• DOI: 10.1093/ije/dyae116

Abstract Background COVID-19 vaccine effectiveness (VE) studies leveraging systematic surveillance in sub-Saharan Africa are limited. We assessed the effectiveness of two vaccines (Pfizer BNT162b2 and Johnson & Johnson Ad26.COV2.S) against SARS-CoV-2-associated hospitalization in South African adults aged ≥18 years. Methods We conducted a test-negative case-control study using pneumonia surveillance data in South Africa. Inpatients with physician-diagnosed lower respiratory tract infection or suspected COVID-19, testing SARS-CoV-2 positive or negative from June 2021–March 2022, were cases or controls, respectively. Fully vaccinated individuals received one Ad26.COV2.S dose or two BNT162b2 doses ≥14-days before enrollment. VE was estimated using multivariable logistic regression for Delta- and Omicron BA.1/BA.2-predominant periods, stratified by age and HIV status. Results The study included 925 cases and 1890 controls; 38 (4%) cases and 186 (10%) controls were fully vaccinated with BNT162b2, and 30 (3%) cases and 94 (5%) controls with Ad26.COV2.S. The vaccine effectiveness of BNT162b2 against SARS-CoV-2-associated hospitalization over Delta and Omicron BA.1/BA.2 periods was 91% (95% CI: 52%, 98%) and 33% (-16%, 86%), respectively. The vaccine effectiveness of Ad26.COV2.S against hospitalization over Delta and Omicron BA.1/BA.2 periods was 72% (-36% ,94%), and -19% (-130%, 39%), respectively. The vaccine effectiveness of BNT162b2 against hospitalization over the Delta period was 94% (50%, 99%) and 89% (27%, 98%) among adults aged ≥60 years and HIV-uninfected, respectively. Conclusions The BNT162b2 vaccine was effective against SARS-CoV-2-associated hospitalization during the Delta period for adults aged ≥18 years, ≥60 years and those HIV-uninfected. VE for Ad26.COV2.S was inconclusive, potentially due to limited sample size or residual confounding. These findings highlight the utility of sentinel surveillance for estimating VE.