Omicron (BA.1) SARS-CoV-2 variant is associated with reduced risk of hospitalization a...
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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
André Peralta-Santos, Eduardo Freire Rodrigues, Joana Moreno, Vasco Ricoca, Pedro Casaca, Eugenia Fernandes, View ORCID ProfileJoão Paulo Gomes, Rita Ferreira, Joana Isidro, Miguel Pinto, Vítor Borges, Luís Vieira, Sílvia Duarte, Carlos Sousa, José Pedro Almeida, Luís Menezes, Bibiana I. Ferreira, Ana Matias, Ana Pelerito, Samanta Freire, Teresa Grilo, Cláudia Medeiros Borges, Vera Moutinho, Andreia Leite, Irina Kislaya, Ana Paula Rodrigues, Pedro Pinto Leite, Baltazar Nunes
Abstract
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.
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).
