Bibliografie

(eng): The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evades immunity conferred by vaccines and previous infections. We used a Cox proportional hazards model and a logistic regression on individual-level population-wide data from the Czech Republic to estimate risks of infection and hospitalization, including severe states. A recent (≤2 months) full vaccination reached vaccine effectiveness (VE) of 43% (95% confidence interval [CI], 42%–44%) against infection by Omicron compared to 73% (95% CI, 72%–74%) against Delta. A recent booster increased VE to 56% (95% CI, 55%–56%) against Omicron infection compared to 90% (95% CI, 90%–91%) for Delta. The VE against Omicron hospitalization of a recent full vaccination was 45% (95% 95% CI, 29%–57%), with a recent booster 87% (95% CI, 84%–88%). The VE against the need for oxygen therapy due to Omicron was 57% (95% CI, 32%–72%) for recent vaccination, 90% (95% CI, 87%–92%) for a recent booster. Postinfection protection against Omicron hospitalization declined from 68% (95% CI, 68%–69%) at ≤6 months to 13% (95% CI, 11%–14%) at >6 months after a previous infection. The odds ratios for Omicron relative to Delta were 0.36 (95% CI, .34–.38) for hospitalization, 0.24 (95% CI, .22–.26) for oxygen, and 0.24 (95% CI, .21–.28) for intensive care unit admission. Recent vaccination still brings substantial protection against severe outcome for Omicron.