Omicron (BA.1) SARS-CoV-2 Variant Is Associated With Reduced Risk of Hospitalization and Length of Stay Compared With Delta (B.1.617.2)

Peralta‐Santos, André; Rodrigues, Eduardo Freire; Moreno, Joana; Ricoca, Vasco; Casaca, Pedro; Fernandes, Eugénia M.; Gomes, João Paulo; Ferreira, Rita; Isidro, Joana; Pinto, Miguel; Borges, Vítor; Vieira, Luı́s; Duarte, Sílvia; Sousa, Carlos; Almeida, José Pedro; Menezes, Luís; Ferreira, Bibiana I.; Matias, Ana Catarina; Pelerito, Ana; Freire, Samanta; Grilo, Teresa; Borges, Cláudia Medeiros; Moutinho, Vera; Leite, Andreia; Kislaya, Irina; Rodrigues, Ana Paula; Leite, Pedro Pinto; Nunes, Baltazar

doi:10.2139/ssrn.4017381

Cited by 23 publications

(21 citation statements)

References 4 publications

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“…In the group of No-Vax patients, in accordance with the epidemiological data in Italy related to the period between November 2021 and February 2022, the Delta variant was more frequently detected in comparison with the Omicron. However, in contrast to the results of a previous study showing a substantially reduced overall severity of the Omicron variant compared to the Delta, in our group of unvaccinated patients, infection by the Omicron variant was associated with a greater severity of respiratory failure and a higher rate of death [ 57 ]. In the group of vaccinated patients, no significant differences were observed in the course of the disease between the Omicron and Delta strains.…”

Section: Discussioncontrasting

confidence: 99%

Evolution of the Clinical Profile and Outcomes of Unvaccinated Patients Affected by Critical COVID-19 Pneumonia from the Pre-Vaccination to the Post-Vaccination Waves in Italy

et al. 2022

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The vaccination campaign and the new SARS-CoV-2 variants may have changed the clinical profile and outcomes of patients admitted to sub-intensive unit care. We conducted a retrospective study aimed to compare the clinical and radiological features of unvaccinated critical COVID-19 patients hospitalized during the last pandemic wave (December 2021–February 2022, No-Vax group) and before starting the vaccination campaign (March–December 2020, Pre-Vax group). The No-Vax group was also compared with vaccinated patients of the same pandemic wave (Vax group). With respect to the Pre-Vax group, the No-Vax group contained a higher percentage of smokers (p = 0.0007) and a lower prevalence of males (p = 0.0003). At admission, the No-Vax patients showed both a higher CT score of pneumonia and a worse severe respiratory failure (p < 0.0001). In the No-Vax group, a higher percentage of deaths occurred, though this was not significant. In comparison with the No-Vax group, the Vax patients were older (p = 0.0097), with a higher Charlson comorbidity index (p < 0.0001) and a significantly lower HRCT score (p = 0.0015). The percentage of deaths was not different between the two groups. The No-Vax patients showed a more severe disease in comparison with the Pre-Vax patients, and were younger and had fewer comorbidities than the Vax patients.

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Section: Discussioncontrasting

confidence: 99%

Evolution of the Clinical Profile and Outcomes of Unvaccinated Patients Affected by Critical COVID-19 Pneumonia from the Pre-Vaccination to the Post-Vaccination Waves in Italy

et al. 2022

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“…Our estimates of hospitalization risk following infection with Delta (HR 2.28 95% CI 1.56-3.34) are similar to those from Scotland (HR 1.85 95% CI 1.39-2.47) (12) and Public Health England (HR 2.61, 95% CI 1.56-4.36) (19). To our knowledge, few studies outside of ours have examined the hospitalization risk of Omicron compared to infection with ancestral lineages, but our estimates of hospitalization risk of Omicron vs Delta are highly similar to those calculated using S-gene target failure (SGTF) data (20)(21)(22). Unlike studies using only SGTF data to identify probable Omicron cases, our study uses genomic sequencing to confirm the variant identity of each case, reducing the risk of misclassification.…”

Section: Discussionmentioning

confidence: 71%

Associations between SARS-CoV-2 variants and risk of COVID-19 hospitalization among confirmed cases in Washington State: a retrospective cohort study

Paredes

Lunn

Famulare

et al. 2021

Preprint

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Background: The COVID–19 pandemic is now dominated by variant lineages; the resulting impact on disease severity remains unclear. Using a retrospective cohort study, we assessed the risk of hospitalization following infection with nine variants of concern or interest (VOC/VOI). Methods: Our study includes individuals with positive SARS–CoV–2 RT PCR in the Washington Disease Reporting System and with available viral genome data, from December 1, 2020 to July 30, 2021. The main analysis was restricted to cases with specimens collected through sentinel surveillance. Using a Cox proportional hazards model with mixed effects, we estimated hazard ratios (HR) for the risk of hospitalization following infection with a VOC/VOI, adjusting for age, sex, and vaccination status. Findings: Of the 27,814 cases, 23,170 (83.3%) were sequenced through sentinel surveillance, of which 726 (3.1%) were hospitalized due to COVID–19. Higher hospitalization risk was found for infections with Gamma (HR 3.17, 95% CI 2.15–4.67), Beta (HR: 2.97, 95% CI 1.65–5.35), Delta (HR: 2.30, 95% CI 1.69–3.15), and Alpha (HR 1.59, 95% CI 1.26–1.99) compared to infections with an ancestral lineage. Following VOC infection, unvaccinated patients show a similar higher hospitalization risk, while vaccinated patients show no significant difference in risk, both when compared to unvaccinated, ancestral lineage cases. Interpretation: Infection with a VOC results in a higher hospitalization risk, with an active vaccination attenuating that risk. Our findings support promoting hospital preparedness, vaccination, and robust genomic surveillance.

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“…The patients admitted during the Omicron wave placed less demand on oxygen supplies, ventilators and ICU beds than patients in the previous waves. Early reports from other countries also suggest reduced severity among hospital admissions in the Omicron wave (15,16).…”

Section: Discussionmentioning

confidence: 94%

Clinical severity of COVID-19 patients admitted to hospitals during the Omicron wave in South Africa

Jassat

Karim

Mudara

et al. 2022

Preprint

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Background: Clinical severity of patients hospitalised with SARS-CoV-2 infection during the Omicron (fourth) wave was assessed and compared to trends in the D614G (first), Beta (second), and Delta (third) waves in South Africa. Methods: Weekly incidence of 30 laboratory-confirmed SARS-CoV-2 cases/100,000 population defined the start and end of each wave. Hospital admission data were collected through an active national COVID-19-specific surveillance programme. Disease severity was compared across waves by post-imputation random effect multivariable logistic regression models. Severe disease was defined as one or more of acute respiratory distress, supplemental oxygen, mechanical ventilation, intensive-care admission or death. Results: 335,219 laboratory-confirmed SARS-CoV-2 admissions were analysed, constituting 10.4% of 3,216,179 cases recorded during the 4 waves. In the Omicron wave, 8.3% of cases were admitted to hospital (52,038/629,617) compared to 12.9% (71,411/553,530) in the D614G, 12.6% (91,843/726,772) in the Beta and 10.0% (131,083/1,306,260) in the Delta waves (p<0.001). During the Omicron wave, 33.6% of admissions experienced severe disease compared to 52.3%, 63.4% and 63.0% in the D614G, Beta and Delta waves (p<0.001). The in-hospital case fatality ratio during the Omicron wave was 10.7%, compared to 21.5%, 28.8% and 26.4% in the D614G, Beta and Delta waves (p<0.001). Compared to the Omicron wave, patients had more severe clinical presentations in the D614G (adjusted odds ratio [aOR] 2.07; 95% confidence interval [CI] 2.01-2.13), Beta (aOR 3.59; CI: 3.49-3.70) and Delta (aOR 3.47: CI: 3.38-3.57) waves. Conclusion: The trend of increasing cases and admissions across South Africa's first three waves shifted in Omicron fourth wave, with a higher and quicker peak but fewer admitted patients, who experienced less clinically severe illness and had a lower case-fatality ratio. Omicron marked a change in the SARS-CoV-2 epidemic curve, clinical profile and deaths in South Africa. Extrapolations to other populations should factor in differing vaccination and prior infection levels.

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Omicron (BA.1) SARS-CoV-2 Variant Is Associated With Reduced Risk of Hospitalization and Length of Stay Compared With Delta (B.1.617.2)

Cited by 23 publications

References 4 publications

Evolution of the Clinical Profile and Outcomes of Unvaccinated Patients Affected by Critical COVID-19 Pneumonia from the Pre-Vaccination to the Post-Vaccination Waves in Italy

Evolution of the Clinical Profile and Outcomes of Unvaccinated Patients Affected by Critical COVID-19 Pneumonia from the Pre-Vaccination to the Post-Vaccination Waves in Italy

Associations between SARS-CoV-2 variants and risk of COVID-19 hospitalization among confirmed cases in Washington State: a retrospective cohort study

Clinical severity of COVID-19 patients admitted to hospitals during the Omicron wave in South Africa

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