ArticleClinical infectious diseases : an official publication of the Infectious Diseases Society of America2022
Two-Dose Severe Acute Respiratory Syndrome Coronavirus 2 Vaccine Effectiveness With Mixed Schedules and Extended Dosing Intervals: Test-Negative Design Studies From British Columbia and Quebec, Canada.
Article in Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. An erratum has been issued. Cited by 105 papers, 7 of them syntheses that pooled it.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
105 citing papers in PubMed, 7 syntheses or guidelines pooled it, 136 citations in OpenAlex.
- Prior infections and effectiveness of SARS-CoV-2 vaccine in test-negative studies: a systematic review and meta-analysis.American journal of epidemiology · 2024Pooled it
- Evaluation of Waning of SARS-CoV-2 Vaccine-Induced Immunity: A Systematic Review and Meta-analysis.JAMA network open · 2023Pooled it
- Long-term effectiveness of COVID-19 vaccines against infections, hospitalisations, and mortality in adults: findings from a rapid living systematic evidence synthesis and meta-analysis up to December, 2022.The Lancet. Respiratory medicine · 2023Pooled it
- Predicting vaccine effectiveness against severe COVID-19 over time and against variants: a meta-analysis.Nature communications · 2023Pooled it
- Analysis of anti-SARS-CoV-2 Omicron-neutralizing antibody titers in different vaccinated and unvaccinated convalescent plasma sources.Nature communications · 2022Pooled it
- Duration of effectiveness of vaccines against SARS-CoV-2 infection and COVID-19 disease: results of a systematic review and meta-regression.Lancet (London, England) · 2022Pooled it
- The effectiveness of BNT162b2 mRNA vaccine against COVID-19 caused by Delta variant of SARS-CoV-2: a systematic review and meta-analysis.Inflammopharmacology · 2022Pooled it
- Seasonal human coronavirus humoral responses in AZD1222 (ChaAdOx1 nCoV-19) COVID-19 vaccinated adults reveal limited cross-immunity.Frontiers in immunology · 2024Trial
- Stochastic interventional approach to assessing immune correlates of protection: Application to the COVE messenger RNA-1273 vaccine trial.International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases · 2023Trial
- The immunogenicity of an extended dosing interval of BNT162b2 against SARS-CoV-2 Omicron variant among healthy school-aged children, a randomized controlled trial.International journal of infectious diseases : IJID : official publication of the International Society for Infectious Diseases · 2023Trial
- Integrating Genomic Data into Test-negative Designs for Estimating Lineage-specific COVID-19 Vaccine Effectiveness.Clinical infectious diseases : an official publication of the Infectious Diseases Society of America · 2026Article
- A comparison of two- and three-dose MVA-BN mpox vaccination series on anti-monkeypox virus immunity.NPJ vaccines · 2026Article
- Effectiveness of 2024/25 KP.2 Vaccine Against Outpatient COVID-19 in Canada.Influenza and other respiratory viruses · 2026Article
- Article
- Effectiveness of ChAdOx1 nCoV-19 (Vaxzevria) primary series vaccine against SARS-CoV-2 beta and delta variants: a nationwide study.BMC infectious diseases · 2025Article
- Neutralizing antibody response to SARS-CoV-2 variants, as determined by the MSD multiplex assay, following COVID-19 vaccination in cancer patients.Vaccine: X · 2025Article
- Evaluating COVID-19 vaccination policy in Québec (Canada) using a data-driven dynamic transmission model.PLoS computational biology · 2025Article
- Comparative duration of neutralizing responses and protections of COVID-19 vaccination and correlates of protection.Nature communications · 2025Article
- Intensity of public health and social measures are associated with effectiveness of SARS-CoV-2 vaccine in test-negative study.medRxiv : the preprint server for health sciences · 2025Article
- Factors Associated With the Transmission of the Delta Severe Acute Respiratory Syndrome Coronavirus 2 Variant in Households: The Israeli COVID-19 Family Study (ICoFS).The Journal of infectious diseases · 2025Article
45 more citing papers are in PubMed but not listed here.
Corrections and comments
- Erratum issued
Authors and funding
31 authors at 9 institutions in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundThe Canadian coronavirus disease 2019 (COVID-19) immunization strategy deferred second doses and allowed mixed schedules. We compared 2-dose vaccine effectiveness (VE) by vaccine type (mRNA and/or ChAdOx1), interval between doses, and time since second dose in 2 of Canada's larger provinces.
methodsTwo-dose VE against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or hospitalization among adults ≥18 years, including due to Alpha, Gamma, and Delta variants of concern (VOCs), was assessed ≥14 days postvaccination by test-negative design studies separately conducted in British Columbia and Quebec, Canada, between 30 May and 27 November (epi-weeks 22-47) 2021.
resultsIn both provinces, all homologous or heterologous mRNA and/or ChAdOx1 2-dose schedules were associated with ≥90% reduction in SARS-CoV-2 hospitalization risk for ≥7 months. With slight decline from a peak of >90%, VE against infection was ≥80% for ≥6 months following homologous mRNA vaccination, lower by ∼10% when both doses were ChAdOx1 but comparably high following heterologous ChAdOx1 + mRNA receipt. Findings were similar by age group, sex, and VOC. VE was significantly higher with longer 7-8-week versus manufacturer-specified 3-4-week intervals between mRNA doses.
conclusionsTwo doses of any mRNA and/or ChAdOx1 combination gave substantial and sustained protection against SARS-CoV-2 hospitalization, spanning Delta-dominant circulation. ChAdOx1 VE against infection was improved by heterologous mRNA series completion. A 7-8-week interval between first and second doses improved mRNA VE and may be the optimal schedule outside periods of intense epidemic surge. Findings support interchangeability and extended intervals between SARS-CoV-2 vaccine doses, with potential global implications for low-coverage areas and, going forward, for children.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.