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Protection by Vaccines and Previous Infection Against the Omicron Variant of Severe Acute Respiratory Syndrome Coronavirus 2

Publication at Faculty of Physical Education and Sport, First Faculty of Medicine, Third Faculty of Medicine |
2022

Abstract

Effectiveness of vaccines and postinfection immunity against the Omicron variant of SARS-CoV-2 is significantly lower than against the Delta variant. The probability of a severe outcome is substantially lower for the Omicron variant compared to Delta.

Background The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evades immunity conferred by vaccines and previous infections. Methods 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.

Results A recent (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.

Conclusions Recent vaccination still brings substantial protection against severe outcome for Omicron.