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.
Creators: name: Davies, Mary-Ann
name: Kassanjee, Reshma
name: Rosseau, Petro
name: Morden, Erna
name: Johnson, Leigh
name: Solomon, Wesley
name: Hsiao, Nei-Yuan
name: Hussey, Hannah
name: Meintjes, Graeme
name: Paleker, Masudah
name: Jacobs, Theuns
name: Raubenheimer, Peter
name: Heekes, Alexa
name: Dane, Pierre
name: Bam, Jamy-Lee
name: Smith, Mariette
name: Preiser, Wolfgang
name: Pienaar, David
name: Mendelson, Marc
name: Naude, Jonathan
name: Schrueder, Neshaad
name: Mnguni, Ayanda
name: Le Roux, Sue
name: Murie, Katie
name: Prozesky, Hans
name: Mahomed, Hassan
name: Rossouw, Liezel
name: Wasserman, Sean
name: Maughan, Deborah
name: Boloko, Linda
name: Smith, Barry
name: Taljaard, Jantjie
name: Symons, Greg
name: Ntusi, Ntobeko AB
name: Parker, Arifa
name: Wolter, Nicole
name: Jassat, Waasila
name: Cohen, Cheryl
name: Lessells, Richard
name: Wilkinson, Robert J
name: Arendse, Juanita
name: Kariem, Saadiq
name: Moodley, Melvin
name: Wolmarans, Milani
name: Cloete, Keith
name: Boulle, Andrew
name: Affiliations, Western Cape and South African National Departments of Health in collaboration with the National Institute for Communicable Diseases in South Africa
Publisher: name: The Francis Crick Institute
Year: 2022
Subjects: classificationCode: Model organisms
subject: Model organisms
classificationCode: Infectious Disease
subject: Infectious Disease
classificationCode: Human Biology & Physiology
subject: Human Biology &amp; Physiology
classificationCode: Immunology
subject: Immunology
subject: FOS: Clinical medicine

description: OBJECTIVES: 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 a modest reduction in risk of severe hospitalization or death compared to the Delta-driven wave.