Portal de Periódicos da CAPES

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)

2022; RELX Group (Netherlands); Linguagem: Inglês

10.2139/ssrn.4017381

1556-5068

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

COVID-19 Clinical Research Studies

Introduction: Early reports showed that Omicron (BA.1) SARS-CoV-2 could be less severe. However, the magnitude of risk reduction of hospitalization and mortality of Omicron (BA.1) infections compared with Delta (B.1.617.2) is not yet clear. This study compares the risk of severe disease among patients infected with the Omicron (BA.1) variant with patients infected with Delta (B.1.617.2) variant in Portugal.Methods: We conducted a cohort study in individuals diagnosed with SARS-CoV-2 infection between 1st and 29th December 2021. Cases were individuals with a positive PCR test notified to the national surveillance system. SARS-CoV-2 variants were classified first by whole genomic sequencing (WGS) and, if this information was unavailable, by detecting the S gene target failure. We considered a hospitalization for all the patients admitted within the 14 days after the SARS-CoV-2 infection; after that period, they were censored.T he comparison of the risk of hospitalization between Omicron (BA.1) and Delta (B.1.617.2) VOC was estimated using a Cox proportional hazards model. The mean length of stay was compared using linear regression, and the risk of death between Omicron and Delta patients was estimated with a penalized logistic regression. All models were adjusted for sex, age, previous infection, and vaccination status.Results: We included 15 978 participants aged 16 or more years old, 9 397 infected by Delta (B.1.617.2) and 6 581 infected with Omicron (BA.1). Within the Delta (B.1.617.2) group, 148 (1.6%) were hospitalized, and 16 (0.2%) were with the Omicron (BA.1). A total of 26 deaths were reported, all in participants with Delta (B.1.617.2) infection. Adjusted HR for hospitalization for the Omicron (BA.1) variant compared with Delta (B.1.617.2) was 0.25 (95%CI 0.15 to 0.43). The length of stay in hospital for Omicron (BA.1) patients was significantly shorter than for Delta (confounding-adjusted difference -4.0 days (95%CI -7.2 to -0.8). The odds of death were 0.14 (95% CI 0.0011 to 1.12), representing a reduction in the risk of death of 86% when infected with Omicron (BA.1) compared with Delta (B.1.617.2).Conclusion: Omicron (BA.1) was associated with a 75% risk reduction of hospitalization compared with Delta (B.1.617.2) and reduced length of hospital stay.Funding Information: None. Declaration of Interests: None.Ethics Approval Statement: The genomic surveillance of SARS-CoV-2 in Portugal is regulated by the Assistant Secretary of State and Health Executive Order (Despacho n.º 331/2021 of January 11, 2021). The research on genomic epidemiology of SARS-COV-2 received the clearance of the Ethics Committee of INSA on March 30, 2021.