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Effectiveness of Coronavirus Disease 2019 Vaccines Against Hospitalization and Death in Canada: A Multiprovincial, Test-Negative Design Study
Nasreen, Sharifa
Febriani, Yossi Velásquez García, Héctor Alexander Zhang, Geng Tadrous, Mina Buchan, Sarah A Righolt, Christiaan H Mahmud, Salaheddin M Janjua, Naveed Zafar Krajden, Mel
Febriani, Yossi
Velásquez García, Héctor Alexander
Zhang, Geng
Tadrous, Mina
Buchan, Sarah A
Righolt, Christiaan H
Mahmud, Salaheddin M
Janjua, Naveed Zafar
Krajden, Mel
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Journal Title
Clinical Infectious Diseases
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Term and Year
Publication Date
2022-08-17
Type
Book Title
Publication Volume
76
Publication Issue
4
Publication Begin
640
Publication End
648
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ciac634.pdf
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Abstract
Background: A major goal of coronavirus disease 2019 (COVID-19) vaccination is to prevent severe outcomes (hospitalizations and deaths). We estimated the effectiveness of messenger RNA (mRNA) and ChAdOx1 COVID-19 vaccines against severe outcomes in 4 Canadian provinces between December 2020 and September 2021.
Methods: We conducted this multiprovincial, retrospective, test-negative study among community-dwelling adults aged ≥18 years in Ontario, Quebec, British Columbia, and Manitoba using linked provincial databases and a common study protocol. Multivariable logistic regression was used to estimate province-specific vaccine effectiveness against COVID-19 hospitalization and/or death. Estimates were pooled using random-effects models.
Results: We included 2 508 296 tested participants, with 31 776 COVID-19 hospitalizations and 5842 deaths. Vaccine effectiveness was 83% after a first dose and 98% after a second dose against both hospitalization and death (separately). Against severe outcomes, effectiveness was 87% (95% confidence interval [CI], 71%-94%) ≥84 days after a first dose of mRNA vaccine, increasing to 98% (95% CI, 96%-99%) ≥112 days after a second dose. Vaccine effectiveness against severe outcomes for ChAdOx1 was 88% (95% CI, 75%-94%) ≥56 days after a first dose, increasing to 97% (95% CI, 91%-99%) ≥56 days after a second dose. Lower 1-dose effectiveness was observed for adults aged ≥80 years and those with comorbidities, but effectiveness became comparable after a second dose. Two doses of vaccines provided very high protection for both homologous and heterologous schedules and against Alpha, Gamma, and Delta variants.
Conclusions: Two doses of mRNA or ChAdOx1 vaccine provide excellent protection against severe outcomes.
Citation
Nasreen S, Febriani Y, Velásquez García HA, Zhang G, Tadrous M, Buchan SA, Righolt CH, Mahmud SM, Janjua NZ, Krajden M, De Serres G, Kwong JC. Effectiveness of Coronavirus Disease 2019 Vaccines Against Hospitalization and Death in Canada: A Multiprovincial, Test-Negative Design Study. Clin Infect Dis. 2023 Feb 18;76(4):640-648. doi: 10.1093/cid/ciac634. PMID: 35974428; PMCID: PMC9384799.