Mallah, NarmeenPardo Seco, Jacobo JoséLópez Pérez, Luis RicardoGonzález Pérez, Juan ManuelRosón Calvo, BenignoOtero Barrós, María TeresaDurán Parrondo, CarmenNartallo Penas, VictoriaMirás Carballal, SusanaRodríguez Tenreiro, CarmenRivero Calle, IreneGómez Carballa, AlbertoSalas Ellacuriaga, AntonioMartinón Torres, Federico2022-11-282022-11-282022Environmental Research 215 (2022) 114252http://hdl.handle.net/10347/29474This work was supported by Framework Partnership Agreement between the Consellería de Sanidad de la XUNTA de Galicia and GENVIP-IDIS-2021–2024 (SERGAS-IDIS March 2021; Spain); and consorcio Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CB21/06/00103; F.M-T), DIAVIR (Instituto de Salud Carlos III (ISCIII)/DTS19/00049/Cofinanciado FEDER; Proyecto de Desarrollo Tecnológico en Salud), Resvi-Omics (Instituto de Salud Carlos III (ISCIII)/PI19/01039/Cofinanciado FEDER), BI-BACVIR (PRIS-3; Agencia de Conocimiento en Salud (ACIS)—Servicio Gallego de Salud (SERGAS)—Xunta de Galicia; Spain), Programa Traslacional COVID-19 (ACIS—Servicio Gallego de Salud (SERGAS)—XUNTA de Galicia; Spain) and Axencia Galega de Innovación (GAIN; IN607B 2020/08—XUNTA de Galicia; Spain) [A.S]; and ReSVinext (Instituto de Salud Carlos III (ISCIII)/PI16/01569/Cofinanciado FEDER), Enterogen (Instituto de Salud Carlos III (ISCIII)/PI19/01090/Cofinanciado FEDER), and Axencia Galega de Innovación (GAIN; IN845D 2020/23—Xunta de Galicia; Spain) [F.M-T]Background: Research on the effectiveness of COVID-19 booster-based vaccine schedule is ongoing and real-world data on vaccine effectiveness (VE) in comorbid patients are limited. We aimed to estimate booster dose VE against SARS-CoV-2 infection and COVID-19 severity in the general population and in comorbid patients. Method: A retrospective test-negative control study was undertaken in Galicia-Spain (December 2020–November 2021). VE and 95% confidence interval (CI) were estimated using multivariate logistic regression models. Results: 1,512,415 (94.13%) negative and 94,334 (5.87%) positive SARS-CoV-2 test results were included. A booster dose of COVID-19 vaccine is associated with substantially higher protection against SARS-CoV-2 infection than vaccination without a booster [VEboosted = 87% (95%CI: 83%; 89%); VEnon-boosted = 66% (95%CI: 65%; 67%)]. The high VE was observed in all ages, but was more pronounced in subjects older than 65 years. VE against COVID-19 severity was analyzed in a mixed population of boosted and non-boosted individuals and considerable protection was obtained [VE: hospitalization = 72% (95%CI: 68%; 75%); intensive care unit administration = 83% (95%CI: 78%; 88%), in-hospital mortality = 66% (95%CI: 53%; 75%)]. Boosted comorbid patients are more protected against SARS-CoV-2 infection than those who were non-boosted. This was observed in a wide range of major diseases including cancer (81% versus 54%), chronic obstructive pulmonary disease (84% versus 61%), diabetes (84% versus 65%), hypertension (82% versus 65%) and obesity (91% versus 67%), among others. Conclusions: A booster dose of COVID-19 vaccine increases the protection against SARS-CoV-2 infection and COVID-19 severity in the general population and in comorbid patients.eng© 2022 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).Attribution-NonCommercial-NoDerivatives 4.0 Internacionalhttp://creativecommons.org/licenses/by-nc-nd/4.0/COVID-19 booster vaccine effectivenessComorbiditiesPopulation-based studySARS-CoV-2Spainjournal article10.1016/j.envres.2022.1142520013-9351open access