Jassat, WaasilaKarim, Salim S. AbdoolOzougwu, LovelynWelch, RichardMudara, CarolineMasha, MaureenRousseau, PetroWolmarans, MilaniSelikow, AnthonyGovender, NevashanWalaza, sibongileVon Gottberg, AnneWolter, NicoleGroome, Michelle J.Pisa, Pedro TerrenceSanne, IanGovender, SharleneCohen, CherylGroome, Michelle J.2024-04-242024-04-242023-04-15Jassat, W., Karim, S.S.A., Ozougwu, L. et al. 2023, 'Trends in cases, hospitalizations, and mortality related to the Omicron BA.4/BA.5 subvariants in South Africa', Clinical Infectious Diseases, vol. 76, no. 8, pp. 1468-1475. https://DOI.org/10.1093/cid/ciac921.1058-4838 (print)1537-6591 (online)10.1093/cid/ciac921http://hdl.handle.net/2263/95743BACKGROUND : 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.en© The Author(s) 2022. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence.Hospital admissionsMortalityOmicron BA.4Omicron BA.5.COVID-19 pandemicCoronavirus disease 2019 (COVID-19)Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)SDG-03: Good health and well-beingHealth sciences articles SDG-03SDG-03: Good health and well-beingArticle