Effectiveness of COVID-19 vaccines against Omicron or Delta symptomatic infection and severe outcomes
Open accessPreprint — published as 10.1001/jamanetworkopen.2022.32760 · Paper page
Abstract
Background: The incidence of SARS-CoV-2 infection, including among those who have received 2 doses of COVID-19 vaccines, increased substantially following the emergence of Omicron in Ontario, Canada. Methods: Applying the test-negative study design to linked provincial databases, we estimated vaccine effectiveness (VE) against symptomatic infection and severe outcomes (hospitalization or death) caused by Omicron or Delta between December 6 and 26, 2021. We used multivariable logistic regression to estimate the effectiveness of 2 or 3 COVID-19 vaccine doses by time since the latest dose, compared to unvaccinated individuals. Results: We included 16,087 Omicron-positive cases, 4,261 Delta-positive cases, and 114,087 test-negative controls. VE against symptomatic Delta infection declined from 89% (95%CI, 86-92%) 7-59 days after a second dose to 80% (95%CI, 74-84%) after ≥240 days, but increased to 97% (95%CI, 96-98%) ≥7 days after a third dose. VE against symptomatic Omicron infection was only 36% (95%CI, 24-45%) 7-59 days after a second dose and provided no protection after ≥180 days, but increased to 61% (95%CI, 56-65%) ≥7 days after a third dose. VE against severe outcomes was very high following a third dose for both Delta and Omicron (99% [95%CI, 98-99%] and 95% [95%CI, 87-98%], respectively). Conclusions: In contrast to high levels of protection against both symptomatic infection and severe outcomes caused by Delta, our results suggest that 2 doses of COVID-19 vaccines only offer modest and short-term protection against symptomatic Omicron infection. A third dose improves protection against symptomatic infection and provides excellent protection against severe outcomes for both variants.
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Consistent findings were reached, indicating rapid waning of vaccine protection against symptomatic Omicron infection, consistent with findings of other studies for effectiveness against Omicron infection (with no BA.1/BA.2 subvariant specified).
“Notwithstanding these limitations, consistent findings were reached, indicating rapid waning of vaccine protection against symptomatic Omicron infection that are consistent with findings of other studies for effectiveness against Omicron infection (with no BA.1/BA.2 subvariant specified)42–48.”
From Duration of mRNA vaccine protection against SARS-CoV-2 Omicron BA.1 and BA.2 subvariants in Qatar (2022) · cites this paper as [43]
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References 29 · Cited by 356
Research works printed but not linked: 4
- Sheikh A, Kerr S, Woolhouse M, et al. Severity of Omicron variant of concern and vaccine effectiveness against symptomatic disease: national cohort with nested test negative design study in Scotland. Preprint 2021 [Available from: https://www.pure.ed.ac.uk/ws/portalfiles/portal/245818096/Severity_of_Omicron_variant_of_c oncern_and_vaccine_effectiveness_against_symptomatic_disease.pdf.
- Thompson MG, Natarajan K, Irving SA, et al. Effectiveness of a Third Dose of mRNA Vaccines Against COVID-19-Associated Emergency Department and Urgent Care Encounters and Hospitalizations Among Adults During Periods of Delta and Omicron Variant Predominance - VISION Network, 10 States, August 2021-January 2022. MMWR Morb Mortal Wkly Rep 2022:ePub: 21 January 2022. DOI: http://dx.doi.org/10.15585/mmwr.mm7104e3external. · DOI
- Buchan SA, Chung H, Brown KA, et al. Effectiveness of COVID-19 vaccines against Omicron or Delta infection. medRxiv 2022:2021.12.30.21268565. doi: 10.1101/2021.12.30.21268565
- Pfizer Press Release. Pfizer and BioNTech Provide Update on Omicron Variant 2021 [cited 2021 22 December]. Available from: https://www.pfizer.com/news/press-release/press-release- detail/pfizer-and-biontech-provide-update-omicron-variant.
- Authors
- Buchan, S. A., Chung, H., Brown, K. A., Austin, P. C., Fell, D. B., Gubbay, J. B., Nasreen, S., Schwartz, K. L., Sundaram, M. E., Tadrous, M., Wilson, K., Wilson, S. E., & Kwong, J. C.
- Affiliations
- University of Toronto (CA)
- Institute for Clinical Evaluative Sciences (CA)
- University of Ottawa (CA)
- Marshfield Clinic Research Foundation (US)
- Corresponding author
- Kwong, Jeffrey C.
- ORCID
- Venue
- JAMA Network Open
- Publisher
- openRxiv
- Published
- 2022-01-01
- Volume
- 5
- Issue
- 9
- Pages
- e2232760-e2232760
- ISSN
- 2574-3805 (ISSN-L)
- PMC
- PMC9500552
- OpenAlex
- W4296686923
- Cited by
- 356
- References
- 29
- Citations by year
- 2026: 14 · 2025: 31 · 2024: 67 · 2023: 123 · 2022: 121
- FWCI
- 41.72
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- cc-by
- Locations
- JAMA Network Open (publishedVersion, cc-by)
- medRxiv (acceptedVersion, cc-by-nc-nd)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- Federal Open Science Repository of Canada / Le Dépôt fédéral de science ouverte du Canada (submittedVersion, cc-by)
- SUNY Digital Repository Support (State University of New York System) (submittedVersion, cc-by-nc-nd)
- Funders
- Heart and Stroke Foundation of Canada
- Cancer Care Ontario
- Public Health Agency of Canada (CNF 151944, 151944)
- Public Health Agency
- University of Toronto
- Canadian Immunization Research Network (CNF 151944)
- Canadian Institutes of Health Research (151944, COVID-19, 151944_1)
- Department of Family and Community Medicine, University of Toronto
- Topics
- Health Sciences › Medicine › Infectious Diseases › SARS-CoV-2 and COVID-19 Research
- Physical Sciences › Mathematics › Modeling and Simulation › COVID-19 epidemiological studies
- Health Sciences › Medicine › Infectious Diseases › COVID-19 Clinical Research Studies
- Keywords
- COVID-19 vaccines, vaccine effectiveness, Omicron variant, Delta variant, SARS-CoV-2, symptomatic infection, hospitalization, COVID-19 mortality, booster vaccination, test-negative case-control, Ontario, COVID-19 vaccination policy, vaccine hesitancy, health system capacity
- MeSH terms
- COVID-19, SARS-CoV-2, COVID-19 Vaccines, Adult, Hepatitis D, Female, Humans, Influenza, Human, Influenza Vaccines, Male, Ontario, Case-Control Studies
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