Reduced risk of hospitalisation among reported COVID-19 cases infected with the SARS-CoV-2 Omicron BA.1 variant compared with the Delta variant, Norway, December 2021 to January 2022
Lamprini Veneti, Håkon Bøås, Anja Bråthen Kristoffersen, Jeanette Stålcrantz, Karoline Bragstad, Olav Hungnes, Margrethe Larsdatter Storm, Nina Aasand, Gunnar Rø, Jostein Starrfelt, Elina Seppälä, Reidar Kvåle, Line Vold, Karin Nygård, Eirik Alnes Buanes, Robert Whittaker
Abstract
We included 39,524 COVID-19 Omicron and 51,481 Delta cases reported in Norway from December 2021 to January 2022. We estimated a 73% reduced risk of hospitalisation (adjusted hazard ratio: 0.27; 95% confidence interval: 0.20-0.36) for Omicron compared with Delta. Compared with unvaccinated groups, Omicron cases who had completed primary two-dose vaccination 7-179 days before diagnosis had a lower reduced risk than Delta (66% vs 93%). People vaccinated with three doses had a similar risk reduction (86% vs 88%).