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Risk reduction of hospitalisation and severe disease in vaccinated COVID-19 cases during the SARS-CoV-2 variant Omicron BA.1-predominant period, Navarre, Spain, January to March 2022
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View Affiliations Hide AffiliationsJesús Castillajcastilc navarra.es
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Members of the Working Group for the Study of COVID-19 in Navarra: Miguel Fernández-Huerta, Carmen Martín, María Eugenia Portillo, Ingrid Estévez, Igberto Tordoya, Delia Quílez, Francisco Lameiro, Ana Isabel Álvaro, Eva Ardanaz, Fernando Baigorria, Aurelio Barricarte, Nerea Egüés, Manuel García Cenoz, Nerea Iriarte, Conchi Moreno-Iribas, Carmen SayónView Citation Hide Citation
Citation style for this article: . Risk reduction of hospitalisation and severe disease in vaccinated COVID-19 cases during the SARS-CoV-2 variant Omicron BA.1-predominant period, Navarre, Spain, January to March 2022. Euro Surveill. 2023;28(5):pii=2200337. https://doi.org/10.2807/1560-7917.ES.2023.28.5.2200337 Received: 08 Apr 2022; Accepted: 12 Sept 2022
Abstract
As COVID-19 vaccine effectiveness against SARS-CoV-2 infection was lower for cases of the Omicron vs the Delta variant, understanding the effect of vaccination in reducing risk of hospitalisation and severe disease among COVID-19 cases is crucial.
To evaluate risk reduction of hospitalisation and severe disease in vaccinated COVID-19 cases during the Omicron BA.1-predominant period in Navarre, Spain.
A case-to-case comparison included COVID-19 epidemiological surveillance data in adults ≥ 18 years from 3 January–20 March 2022. COVID-19 vaccination status was compared between hospitalised and non-hospitalised cases, and between severe (intensive care unit admission or death) and non-severe cases using logistic regression models.
Among 58,952 COVID-19 cases, 565 (1.0%) were hospitalised and 156 (0.3%) were severe. The risk of hospitalisation was reduced within the first 6 months after full COVID-19 vaccination (complete primary series) (adjusted odds ratio (aOR): 0.06; 95% CI: 0.04–0.09) and after 6 months (aOR: 0.16; 95% CI: 0.12–0.21; pcomparison < 0.001), as well as after a booster dose (aOR: 0.06: 95% CI: 0.04–0.07). Similarly, the risk of severe disease was reduced (aOR: 0.13, 0.18, and 0.06, respectively). Compared with cases fully vaccinated 6 months or more before a positive test, those who had received a booster dose had lower risk of hospitalisation (aOR: 0.38; 95% CI: 0.28–0.52) and severe disease (aOR: 0.38; 95% CI: 0.21–0.68).
Full COVID-19 vaccination greatly reduced the risk of hospitalisation and severe outcomes in COVID-19 cases with the Omicron variant, and a booster dose improved this effect in people aged over 65 years.
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