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[Preprint]. 2022 Jan 12:2022.01.12.22269148.
doi: 10.1101/2022.01.12.22269148.

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

Mary-Ann Davies  1   2   3 , Reshma Kassanjee  2 , Petro Rosseau  4 , Erna Morden  1   3 , Leigh Johnson  2 , Wesley Solomon  4 , Nei-Yuan Hsiao  5   6 , Hannah Hussey  1   3 , Graeme Meintjes  7   8 , Masudah Paleker  1   9 , Theuns Jacobs  1 , Peter Raubenheimer  7   8 , Alexa Heekes  1   2 , Pierre Dane  1   2 , Jamy-Lee Bam  1 , Mariette Smith  1   2 , Wolfgang Preiser  6   10 , David Pienaar  11 , Marc Mendelson  7   8 , Jonathan Naude  12 , Neshaad Schrueder  13   14 , Ayanda Mnguni  15 , Sue Le Roux  7   8 , Katie Murie  16 , Hans Prozesky  13   14 , Hassan Mahomed  9   17 , Liezel Rossouw  16 , Sean Wasserman  7   8 , Deborah Maughan  7   8 , Linda Boloko  7   8 , Barry Smith  7   8 , Jantjie Taljaard  13   14 , Greg Symons  7   8 , Ntobeko Ntusi  7   8 , Arifa Parker  13   14 , Nicole Wolter  18 , Waasila Jassat  18 , Cheryl Cohen  18   19 , Richard Lessells  20 , Robert J Wilkinson  21   22   22 , Juanita Arendse  16 , Saadiq Kariem  16 , Melvin Moodley  1 , Krish Vallabhjee  16 , Milani Wolmarans  4 , Keith Cloete  16 , Andrew Boulle  1   2   3
Affiliations

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

Mary-Ann Davies et al. medRxiv. .

Update in

  • 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.
    Davies MA, Kassanjee R, Rousseau P, Morden E, Johnson L, Solomon W, Hsiao NY, Hussey H, Meintjes G, Paleker M, Jacobs T, Raubenheimer P, Heekes A, Dane P, Bam JL, Smith M, Preiser W, Pienaar D, Mendelson M, Naude J, Schrueder N, Mnguni A, Le Roux S, Murie K, Prozesky H, Mahomed H, Rossouw L, Wasserman S, Maughan D, Boloko L, Smith B, Taljaard J, Symons G, Ntusi NAB, Parker A, Wolter N, Jassat W, Cohen C, Lessells R, Wilkinson RJ, Arendse J, Kariem S, Moodley M, Wolmarans M, Cloete K, Boulle A; Western Cape and South African National Departments of Health in collaboration with the National Institute for Communicable Diseases in South Africa Affiliations. Davies MA, et al. Trop Med Int Health. 2022 Jun;27(6):564-573. doi: 10.1111/tmi.13752. Epub 2022 May 10. Trop Med Int Health. 2022. PMID: 35411997 Free PMC article.

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.

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Figures

Figure 1:
Figure 1:
Daily new cases (7 day moving average) by days since start of each wave in Khayelitsha sub-district, Cape Town, South Africa.
Figure 2:
Figure 2:
Adjusted hazard ratio for associations between a) vaccination and b) prior diagnosed infection and different severe COVID-19 outcomes adjusted for patient characteristics, subdistrict, vaccination, and prior diagnosed infection using Cox regression.
See this image and copyright information in PMC

References

    1. Scott L, Hsiao N-y, Moyo S, Singh L, Tegally H, Dor G, et al. Track Omicron’s spread with molecular data. Science. 2021;374(6574):1454–5. - PubMed
    1. Viana R, Moyo S, Amoako DG, Tegally H, Scheepers C, Althaus CL, et al. Rapid epidemic expansion of the SARS-CoV-2 Omicron variant in southern Africa. medRxiv. 2021: - PMC - PubMed
    1. Cele S, Jackson L, Khan K, Khoury DS, Moyo-Gwete T, Tegally H, et al. SARS-CoV-2 Omicron has extensive but incomplete escape of Pfizer BNT162b2 elicited neutralization and requires ACE2 for infection. MedRxiv. 2021. doi: 10.1101/2021.12.19.21268028. Accessed 31 December 2021. - DOI
    1. Pearson CAB, Silal SP, Li MWZ, Dushoff J, Bolker BM, Abbott S, et al. Bounding the levels of transmissibility and immune evasion of the Omicron variant in South Africa. MedRxiv. 2021. doi: 10.1101/2021.12.19.21268038. Accessed 31 December 2021. - DOI
    1. Pulliam JRC, van Schalkwyk C, Govender N, von Gottberg A, Cohen C, Groome MJ, et al. Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa. MedRxiv. 2021. doi: 10.1101/2021.11.11.21266068. Accessed 16 December 2021. - DOI - PMC - PubMed

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