ArticleNature communications2021
Effectiveness of ChAdOx1 vaccine in older adults during SARS-CoV-2 Gamma variant circulation in São Paulo.
Article in Nature communications, 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 49 papers, 5 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.
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Who cites it
49 citing papers in PubMed, 5 syntheses or guidelines pooled it, 80 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
- Clinical Severity of SARS-CoV-2 Variants during COVID-19 Vaccination: A Systematic Review and Meta-Analysis.Viruses · 2023Pooled it
- Vaccine efficacy against SARS-CoV-2 for Pfizer BioNTech, Moderna, and AstraZeneca vaccines: a systematic review.Frontiers in public health · 2023Pooled it
- Effectiveness of COVID-19 vaccines against SARS-CoV-2 variants of concern: a systematic review and meta-analysis.BMC medicine · 2022Pooled it
- Real-Word Effectiveness of Global COVID-19 Vaccines Against SARS-CoV-2 Variants: A Systematic Review and Meta-Analysis.Frontiers in medicine · 2022Pooled it
- Observational methods for COVID-19 vaccine effectiveness research: an empirical evaluation and target trial emulation.International journal of epidemiology · 2024Trial
- Review
- Impact of vaccination and SARS-CoV-2 variants on severe COVID-19 outcomes: a cross-sectional study, Brazil, 2021-2022.Epidemiologia e servicos de saude : revista do Sistema Unico de Saude do Brasil · 2025Article
- Article
- Bias and negative values of COVID-19 vaccine effectiveness estimates from a test-negative design without controlling for prior SARS-CoV-2 infection.Nature communications · 2024Article
- Estimated Deaths Averted in Adults by COVID-19 Vaccination in Select Latin American and Caribbean Countries.Open forum infectious diseases · 2024Article
- Effectiveness of COVID-19 vaccines against severe COVID-19 among patients with cancer in Catalonia, Spain.Nature communications · 2024Article
- Effectiveness of the fourth dose of COVID-19 vaccines against severe COVID-19 among adults 40 years or older in Brazil: a population-based cohort study.Lancet regional health. Americas · 2024Article
- Article
- Double Negative Control Inference in Test-Negative Design Studies of Vaccine Effectiveness.Journal of the American Statistical Association · 2024Article
- COVID-19 vaccine effectiveness against hospitalizations in Paraguay, May 2021-April 2022: A test-negative design.Vaccine · 2023Article
- Computational analysis of the sequence-structure relation in SARS-CoV-2 spike protein using protein contact networks.Scientific reports · 2023Article
- Primary and booster vaccination in reducing severe clinical outcomes associated with Omicron Naïve infection.Journal of infection and public health · 2023Observational
- Effectiveness of COVID-19 Vaccines in Adults with Diabetes Mellitus: A Systematic Review.Vaccines · 2022Review
- Article
Corrections and comments
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Authors and funding
20 authors at 9 institutions in 3 countries.
Funding
Abstract
A two-dose regimen of the Oxford-AstraZeneca (ChAdOx1) Covid-19 vaccine with an inter-dose interval of three months has been implemented in many countries with restricted vaccine supply. However, there is limited evidence for the effectiveness of ChAdOx1 by dose in elderly populations in countries with high prevalence of the Gamma variant of SARS-CoV-2. Here, we estimate ChAdOx1 effectiveness by dose against the primary endpoint of RT-PCR-confirmed Covid-19, and secondary endpoints of Covid-19 hospitalization and Covid-19-related death, in adults aged ≥60 years during an epidemic with high Gamma variant prevalence in São Paulo state, Brazil using a matched, test-negative case-control study. Starting 28 days after the first dose, effectiveness of a single dose of ChAdOx1 is 33.4% (95% CI, 26.4-39.7) against Covid-19, 55.1% (95% CI, 46.6-62.2) against hospitalization, and 61.8% (95% CI, 48.9-71.4) against death. Starting 14 days after the second dose, effectiveness of the two-dose schedule is 77.9% (95% CI, 69.2-84.2) against Covid-19, 87.6% (95% CI, 78.2-92.9) against hospitalization, and 93.6% (95% CI, 81.9-97.7) against death. Completion of the ChAdOx1 vaccine schedule affords significantly increased protection over a single dose against mild and severe Covid-19 outcomes in elderly individuals during widespread Gamma variant circulation.
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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.