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Background: As Omicron became the dominant variant in South Africa, little is known about the severity of its clinical presentation. We describe the clinical severity of patients hospitalised with SARS-CoV-2 infection during the first four weeks of the Omicron-dominated fourth wave and compare this to the first four weeks of the Betadominated second and Delta-dominated third waves in Gauteng Province.
Methods: Polymerase chain reaction and antigen positive SARS-CoV-2 case data were collated daily from laboratory reports. Data on hospital admissions were collected through an active surveillance programme established specifically for COVID-19. In addition to descriptive statistics, post-imputation random effect multivariable logistic regression models were used to compare disease severity in the three wave periods. Severe disease was defined as one or more of acute respiratory distress, supplemental oxygen, mechanical ventilation, high/intensive care or death.
Results: There were 41,046, 33,423, and 133,551 SARS-CoV-2 cases in the second, third and fourth waves respectively. About 4.9% of cases were admitted to hospital during the fourth wave compared to 18.9% and 13.7% during the second and third waves (p<0.001). During the fourth wave, 28.8% of admissions were severe disease compared to 60.1% and 66.9% in the second and third waves (p<0.001). Admitted patients in the omicron-dominated fourth wave were 73% less likely to have severe disease than patients admitted during the delta-dominated third wave (adjusted odds ratio [aOR] 0.27, 95% confidence interval [CI] 0.25-0.31).
Conclusion: The proportion of cases admitted was lower and those admitted were less severe during the first four weeks of the Omicron-dominated fourth wave in Gauteng province of South Africa. Since any combination of a less-virulent virus, comorbidities, high immunity from prior infection(s) or vaccination may be important contributors to this clinical presentation, care should be taken in extrapolating this to other populations with different co-morbidity profiles, prevalence of prior infection and vaccination coverage.
Preprint to be published in The Lancet available (Dec. 29, 2021):
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3996320
