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. 2024 Aug 14;53(5):dyae116.
doi: 10.1093/ije/dyae116.

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

Nicola Chiwandire  1 , Sibongile Walaza  1   2 , Anne von Gottberg  1   3 , Nicole Wolter  1   3 , Mignon Du Plessis  1   3 , Fahima Moosa  1   3 , Michelle J Groome  1   3 , Jeremy Nel  4 , Ebrahim Variava  4   5 , Halima Dawood  6 , Mvuyo Makhasi  1   2 , Leora R Feldstein  7 , Perrine Marcenac  8 , Kathryn E Lafond  8 , Aaron M Samuels  8   9 , Cheryl Cohen  1   2
Affiliations

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

Nicola Chiwandire et al. Int J Epidemiol. .

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.

Keywords: COVID-19; SARS-CoV-2; sentinel surveillance; test-negative case control; vaccine effectiveness.

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Conflict of interest statement

C.C. has received grant support from Sanofi Pasteur, US CDC, Wellcome Trust, Programme for Applied Technologies in Health (PATH), Bill & Melinda Gates Foundation and South African Medical Research Council (SA-MRC). S.M. has received an investigational grant from Sanofi Pasteur and funding from the US CDC. A.v.G. and N.W. have received grant support from Sanofi and the Bill & Melinda Gates Foundation. M.G. has received grants from the Bill & Melinda Gates Foundation and South African Medical Research Council. H.D. reports personal fees from Pfizer‐South Africa and conference attendance sponsorship from MSD‐South Africa, Pfizer‐South Africa and Biomiereux‐South Africa. J.N. reports grant support from the Bill & Melinda Gates Foundation and the Wellcome Trust. The remaining authors declare no conflict of interest.

Figures

Figure 1.
Figure 1.
Number of SARS-CoV-2 cases by epidemiological week and SARS-CoV-2 variant among all adult inpatients enrolled in pneumonia surveillance in South Africa, 19 April 2020 to 31 March 2022. The BNT162b2 vaccine is an mRNA COVID-19 vaccine manufactured by Pfizer-BioNTech, and the Ad26.COV2.S vaccine is a viral vector COVID-19 vaccine manufactured by Johnson & Johnson
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