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. 2022 Oct 17;226(8):1385-1390.
doi: 10.1093/infdis/jiac161.

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

Martin Šmíd  1   2 , Luděk Berec  2   3   4 , Lenka Přibylová  5 , Ondřej Májek  6   7 , Tomáš Pavlík  6   7 , Jiří Jarkovský  6   7 , Jakub Weiner  1   2 , Tamara Barusová  8   9 , Jan Trnka  10
Affiliations

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

Martin Šmíd et al. J Infect Dis. .

Erratum in

Abstract

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 (≤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.

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

Keywords: COVID-19; Omicron variant; SARS-CoV-2; hospitalization; postinfection immunity; vaccine effectiveness.

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Conflict of interest statement

Potential conflicts of interest. The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

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Supplementary concepts