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. 2022 Aug;292(2):377-384.
doi: 10.1111/joim.13504. Epub 2022 May 17.

Adults hospitalized with breakthrough COVID-19 have lower mortality than matched unvaccinated adults

Laura C Myers  1 , Patricia Kipnis  1 , John Greene  1 , Brian Lawson  1 , Gabriel J Escobar  1 , Bruce H Fireman  1 , Nicola P Klein  1 , Vincent X Liu  1
Affiliations

Adults hospitalized with breakthrough COVID-19 have lower mortality than matched unvaccinated adults

Laura C Myers et al. J Intern Med. 2022 Aug.

Abstract

Background: Coronavirus disease 2019 (COVID-19) breakthrough infections are common.

Objective: Evaluate in-hospital mortality of patients with COVID-19 by vaccination status using retrospective cohort study.

Methods: We generated propensity scores for receipt of full vaccination in adults requiring supplemental oxygen hospitalized at Kaiser Permanente Northern California (1 April 2021 to 30 November 2021) with positive severe acute respiratory syndrome coronavirus 2 polymerase chain reaction tests. Optimal matching of fully vaccinated/unvaccinated patients was performed comparing in-hospital mortality.

Results: Of 7305 patients, 1463 (20.0%) were full, 138 (1.9%) were partial, and 5704 (78.1%) were unvaccinated. Fully vaccinated were older than partial or unvaccinated (71.0, 63.0, and 54.0 years, respectively, p < 0.001) with more comorbidities (Comorbidity Point Scores 33.0, 22.0, and 10.0, p < 0.001) and immunosuppressant (11.5%, 8.7%, and 3.0%, p < 0.001) or chemotherapy exposure (2.8%, 0.7%, and 0.4%, p < 0.001). Fewer fully vaccinated patients died compared to matched unvaccinated (9.0% vs. 16.3%, p < 0.0001).

Conclusion: Fully vaccinated patients are less likely to die compared to matched unvaccinated patients.

Keywords: COVID-19; breakthrough infection; hospitalization; mortality; vaccination.

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Conflict of interest statement

Nicola P. Klein reports research support from Pfizer for COVID vaccine trials and from Pfizer, Merck, Sanofi Pasteur, GlaxoSmithKline, and Protein Science (now Sanofi Pasteur) for unrelated research. Gabriel J. Escobar, Vincent X. Liu, and Laura C. Myers report research support from Astra Zeneca unrelated to vaccine research. The other authors have no conflict of interest.

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