ArticleClinical infectious diseases : an official publication of the Infectious Diseases Society of America2023
Relative Virulence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Among Vaccinated and Unvaccinated Individuals Hospitalized With SARS-CoV-2.
Article in Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 2023. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 14 papers.
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Who cites it
14 citing papers in PubMed.
- COVID-19 vaccination and use of antibiotics in COVID-19 patients: a systematic review and meta-analysis.Infection prevention in practice · 2025Review
- Derivation and validation of a point-based forecasting tool for SARS-CoV-2 critical care occupancy: a population-based modeling study.Lancet regional health. Americas · 2025Article
- Impact of adjustment for differential testing by age and sex on apparent epidemiology of SARS-CoV- 2 infection in Ontario, Canada.BMC infectious diseases · 2025Article
- Booster vaccines dose reduced mortality in hospitalized COVID-19 patients requiring oxygen supplementation: Evidence from the Beijing Omicron outbreak.Human vaccines & immunotherapeutics · 2024Article
- Impact of community mask mandates on SARS-CoV-2 transmission in Ontario after adjustment for differential testing by age and sex.PNAS nexus · 2024Article
- Comparative analysis of clinical characteristics of COVID-19 among vaccinated and unvaccinated patients in a major treatment facility in Ghana.Ghana medical journal · 2023Article
- Integrated Management Systems (IMS) to Support and Sustain Quality One Health Services: International Lessons from the COVID-19 Pandemic by the IMIA Primary Care Working Group.Yearbook of medical informatics · 2023Article
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- The COVID-19 Vaccination Coverage in ICU Patients with Severe COVID-19 Infection in a Country with Low Vaccination Coverage-A National Retrospective Analysis.Journal of clinical medicine · 2023Article
- The Impact and Progression of the COVID-19 Pandemic in Bulgaria in Its First Two Years.Vaccines · 2022Article
- Predicting COVID-19 disease severity from SARS-CoV-2 spike protein sequence by mixed effects machine learning.Computers in biology and medicine · 2022Article
- SARS-CoV-2 Vaccination in Solid-Organ Transplant Recipients.Vaccines · 2022Review
- Effect of intermediate/high versus low dose heparin on the thromboembolic and hemorrhagic risk of unvaccinated COVID-19 patients in the emergency department.BMC emergency medicine · 2022Article
Corrections and comments
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Authors and funding
5 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundThe rapid development of safe and effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a singular scientific achievement. Confounding due to health-seeking behaviors, circulating variants, and differential testing by vaccination status may bias analyses toward an apparent increase in infection severity following vaccination.
methodsWe used data from the Ontario, Canada, Case and Contact Management Database and a provincial vaccination dataset (COVaxON) to create a time-matched cohort of individuals who were hospitalized with SARS-CoV-2 infection. Vaccinated individuals were matched to up to 5 unvaccinated individuals based on test date. Risk of intensive care unit (ICU) admission and death were evaluated using conditional logistic regression.
resultsIn 20 064 individuals (3353 vaccinated and 16 711 unvaccinated) hospitalized with infection due to SARS-CoV-2 between 1 January 2021 and 5 January 2022, vaccination with 1, 2, or 3 doses significantly reduced the risk of ICU admission and death. An inverse dose-response relationship was observed between vaccine doses received and both outcomes (adjusted odds ratio [aOR] per additional dose for ICU admission, 0.66; 95% confidence interval [CI], .62 to .71; aOR for death, 0.78; 95% CI, .72 to .84).
conclusionsWe identified decreased virulence of SARS-CoV-2 infections in vaccinated individuals, even when vaccines failed to prevent infection sufficiently severe to cause hospitalization. Even with diminished efficacy of vaccines against infection with novel variants of concern, vaccines remain an important tool for reduction of ICU admission and mortality.
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