The Francis Crick Institute
Tropical Med Int Health - 2022 - Davies - Outcomes of laboratory‐confirmed SARS‐CoV‐2 infection in the Omicron‐driven.pdf (456.29 kB)

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.

Download (456.29 kB)
journal contribution
posted on 2022-06-09, 10:40 authored by Mary-Ann Davies, Reshma Kassanjee, Petro Rosseau, Erna Morden, Leigh Johnson, Wesley Solomon, Nei-Yuan Hsiao, Hannah Hussey, Graeme Meintjes, Masudah Paleker, Theuns Jacobs, Peter Raubenheimer, Alexa Heekes, Pierre Dane, Jamy-Lee Bam, Mariette Smith, Wolfgang Preiser, David Pienaar, Marc Mendelson, Jonathan Naude, Neshaad Schrueder, Ayanda Mnguni, Sue Le Roux, Katie Murie, Hans Prozesky, Hassan Mahomed, Liezel Rossouw, Sean Wasserman, Deborah Maughan, Linda Boloko, Barry Smith, Jantjie Taljaard, Greg Symons, Ntobeko AB Ntusi, Arifa Parker, Nicole Wolter, Waasila Jassat, Cheryl Cohen, Richard Lessells, Robert J Wilkinson, Juanita Arendse, Saadiq Kariem, Melvin Moodley, Milani Wolmarans, Keith Cloete, Andrew Boulle, Western Cape and South African National Departments of Health in collaboration with the National Institute for Communicable Diseases in South Africa Affiliations
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.


Crick (Grant ID: 10218, Grant title: Wilkinson, R FC001218)