1. Outcomes of laboratory-confirmed SARS-CoV-2 infection in the Omicron-driven fourth wave compared with previous waves in the Western Cape Province, South Africa
- Author
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Davies, M-A, Kassanjee, R, Rosseau, P, Morden, E, Johnson, L, Solomon, W, Hsiao, N-Y, Hussey, H, Meintjes, G, Paleker, M, Jacobs, T, Raubenheimer, P, Heekes, A, Dane, P, Bam, J-L, Smith, M, Preiser, W, Pienaar, D, Mendelson, M, Naude, J, Schrueder, N, Mnguni, A, Roux, SL, Murie, K, Prozesky, H, Mahomed, H, Rossouw, L, Wasserman, S, Maughan, D, Boloko, L, Smith, B, Taljaard, J, Symons, G, Ntusi, N, Parker, A, Wolter, N, Jassat, W, Cohen, C, Lessells, R, Wilkinson, RJ, Arendse, J, Kariem, S, Moodley, M, Vallabhjee, K, Wolmarans, M, Cloete, K, Boulle, A, and Wellcome Trust
- Subjects
Model organisms ,Adult ,Male ,sub-Saharan Africa ,2ND WAVES ,COVID-19 Vaccines ,Omicron ,Immunology ,VARIANT ,Infectious Disease ,1ST ,Article ,1117 Public Health and Health Services ,Cohort Studies ,South Africa ,Young Adult ,COVID-19 Testing ,Seroepidemiologic Studies ,Tropical Medicine ,Humans ,prior infection ,Public, Environmental & Occupational Health ,Human Biology & Physiology ,Science & Technology ,Clinical Laboratory Techniques ,SARS-CoV-2 ,FOS: Clinical medicine ,Public Health, Environmental and Occupational Health ,COVID-19 ,vaccination ,immunity ,Infectious Diseases ,Delta ,Western Cape and South African National Departments of Health in collaboration with the National Institute for Communicable Diseases in South Africa Affiliations ,Parasitology ,Female ,Life Sciences & Biomedicine - Abstract
Objectives: We aimed to compare COVID-19 outcomes in the Omicron-driven fourth wave with prior waves in the Western Cape, the contribution of undiagnosed prior infection to differences in outcomes in a context of high seroprevalence due to prior infection, and whether protection against severe disease conferred by prior infection and/or vaccination was maintained. Methods: In this cohort study, we included public sector patients aged ≥20 years with a laboratory confirmed COVID-19 diagnosis between 14 November-11 December 2021 (wave four) and equivalent prior wave periods. We compared the risk between waves of the following outcomes using Cox regression: death, severe hospitalization or death and any hospitalization or death (all ≤14 days after diagnosis) adjusted for age, sex, comorbidities, geography, vaccination and prior infection. Results: We included 5,144 patients from wave four and 11,609 from prior waves. Risk of all outcomes was lower in wave four compared to the Delta-driven wave three (adjusted Hazard Ratio (aHR) [95% confidence interval (CI)] for death 0.27 [0.19; 0.38]. Risk reduction was lower when adjusting for vaccination and prior diagnosed infection (aHR:0.41, 95% CI: 0.29; 0.59) and reduced further when accounting for unascertained prior infections (aHR: 0.72). Vaccine protection was maintained in wave four (aHR for outcome of death: 0.24; 95% CI: 0.10; 0.58). Conclusions: In the Omicron-driven wave, severe COVID-19 outcomes were reduced mostly due to protection conferred by prior infection and/or vaccination, but intrinsically reduced virulence may account for an approximately 25% reduced risk of severe hospitalization or death compared to Delta.
- Published
- 2022