. 2023 Apr 17;76(8):1468-1475.

doi: 10.1093/cid/ciac921.

Trends in Cases, Hospitalizations, and Mortality Related to the Omicron BA.4/BA.5 Subvariants in South Africa

Waasila Jassat^{1

2}, Salim S Abdool Karim^{3

4}, Lovelyn Ozougwu^{1

2}, Richard Welch^{1

2}, Caroline Mudara¹, Maureen Masha^{1

2}, Petro Rousseau⁵, Milani Wolmarans⁵, Anthony Selikow⁶, Nevashan Govender¹, Sibongile Walaza^{1

7}, Anne von Gottberg^{1

8}, Nicole Wolter^{1

8}, Pedro Terrence Pisa^{2

9}, Ian Sanne^{2

10}, Sharlene Govender², Lucille Blumberg^{1

2}, Cheryl Cohen^{1

7}, Michelle J Groome^{1

8}; DATCOV Author Group

Affiliations

¹ National Institute for Communicable Diseases, Division of the National Health Laboratory Service, Johannesburg, South Africa.
² Right to Care, Pretoria, South Africa.
³ Centre for the AIDS Programme of Research in South Africa, Durban, South Africa.
⁴ Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA.
⁵ National Department of Health, Pretoria, South Africa.
⁶ Council for Scientific and Industrial Research, Pretoria, South Africa.
⁷ School of Public Health, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa.
⁸ School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
⁹ Department of Human Nutrition and Dietetics, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
¹⁰ Clinical HIV Research Unit, Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.

PMID: 36453094
PMCID: PMC10110264
DOI: 10.1093/cid/ciac921

Trends in Cases, Hospitalizations, and Mortality Related to the Omicron BA.4/BA.5 Subvariants in South Africa

Waasila Jassat et al. Clin Infect Dis. 2023.

. 2023 Apr 17;76(8):1468-1475.

doi: 10.1093/cid/ciac921.

Authors

Affiliations

¹ National Institute for Communicable Diseases, Division of the National Health Laboratory Service, Johannesburg, South Africa.
² Right to Care, Pretoria, South Africa.
³ Centre for the AIDS Programme of Research in South Africa, Durban, South Africa.
⁴ Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA.
⁵ National Department of Health, Pretoria, South Africa.
⁶ Council for Scientific and Industrial Research, Pretoria, South Africa.
⁷ School of Public Health, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa.
⁸ School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
⁹ Department of Human Nutrition and Dietetics, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
¹⁰ Clinical HIV Research Unit, Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.

PMID: 36453094
PMCID: PMC10110264
DOI: 10.1093/cid/ciac921

Abstract

Background: In this study, we compared admission incidence risk and the risk of mortality in the Omicron BA.4/BA.5 wave to previous waves.

Methods: Data from South Africa's SARS-CoV-2 case linelist, national COVID-19 hospital surveillance system, and Electronic Vaccine Data System were linked and analyzed. Wave periods were defined when the country passed a weekly incidence of 30 cases/100 000 population. In-hospital case fatality ratios (CFRs) during the Delta, Omicron BA.1/BA.2, and Omicron BA.4/BA.5 waves were compared using post-imputation random effect multivariable logistic regression models.

Results: The CFR was 25.9% (N = 37 538 of 144 778), 10.9% (N = 6123 of 56 384), and 8.2% (N = 1212 of 14 879) in the Delta, Omicron BA.1/BA.2, and Omicron BA.4/BA.5 waves, respectively. After adjusting for age, sex, race, comorbidities, health sector, and province, compared with the Omicron BA.4/BA.5 wave, patients had higher risk of mortality in the Omicron BA.1/BA.2 wave (adjusted odds ratio [aOR], 1.3; 95% confidence interval [CI]: 1.2-1.4) and Delta wave (aOR, 3.0; 95% CI: 2.8-3.2). Being partially vaccinated (aOR, 0.9; 95% CI: .9-.9), fully vaccinated (aOR, 0.6; 95% CI: .6-.7), and boosted (aOR, 0.4; 95% CI: .4-.5) and having prior laboratory-confirmed infection (aOR, 0.4; 95% CI: .3-.4) were associated with reduced risks of mortality.

Conclusions: Overall, admission incidence risk and in-hospital mortality, which had increased progressively in South Africa's first 3 waves, decreased in the fourth Omicron BA.1/BA.2 wave and declined even further in the fifth Omicron BA.4/BA.5 wave. Mortality risk was lower in those with natural infection and vaccination, declining further as the number of vaccine doses increased.

Keywords: COVID-19; Omicron BA.4; Omicron BA.5; hospital admissions; mortality.

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Conflict of interest statement

Potential conflicts of interest. S. S. A. K. reports grants or contracts unrelated to this work and paid to institution from the National Institutes of Health, South African Medical Research Council Cooperative Agreement, National Research Foundation/DST, USAID/Right to Care Cooperative agreement, the IQRAA Trust, and EDCTP; an unpaid role as a member of the World Health Organization (WHO) Science Council; a paid role as a member of the Bill and Melinda Gates Foundation (BMGF) Scientific Advisory Committee (meeting honorarium paid to author); and an unpaid role as vice-president of the International Science Council. C. C. reports grants or contracts unrelated to this work and paid to institution from the US Centers for Disease Control and Prevention (CDC), Wellcome Trust, Sanofi Pasteur, PATH, BMGF, and SA-Medical Research Council. A. v. G. reports grants unrelated to this work and paid to institution from the BMGF, Sanofi, CDC, WHO AFRO, Fleming Fund SEQAFRICA, SA MRC, the Solidarity Fund for Innovative Projects, NIH training grant, and ASLM PGI and a role as chair for the National Advisory Group for Immunisation. I. S. reports an institutional grant unrelated to this work from NIH DAIDS–WITS Helen Joseph Hospital CRS. M. J. G. reports grants or contracts unrelated to this work and paid to institution from the South African Medical Research Council and BMGF. N. W. reports grants paid to institution and unrelated to this work from the BMGF, Sanofi, and CDC. R. W. reports shareholding with Adcock Ingram Holdings Ltd, Dischem Pharmacies Ltd, Discovery Ltd, Netcare Ltd, and Aspen Pharmacare Holdings Ltd. S. W. reports grants unrelated to this work and paid to institution from the BMGF, Sanofi, CDC, and Welcome Trust. W. J. reports grants or contracts related to a long coronavirus disease 2019 study, paid to institution, from the BMGF. All remaining authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

Figures

**Figure 1.**
The 7-day moving average of daily severe acute respiratory syndrome coronavirus 2 cases and admissions.

See this image and copyright information in PMC

References

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Trends in Cases, Hospitalizations, and Mortality Related to the Omicron BA.4/BA.5 Subvariants in South Africa

Affiliations

Trends in Cases, Hospitalizations, and Mortality Related to the Omicron BA.4/BA.5 Subvariants in South Africa

Authors

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Abstract

Conflict of interest statement

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