ArticlePloS one2022
COVID-19 vaccine effectiveness against symptomatic SARS-CoV-2 infections, COVID-19 related hospitalizations and deaths, among individuals aged ≥65 years in Portugal: A cohort study based on data-linkage of national registries February-September 2021.
Article in PloS one, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 12 papers, 3 of them syntheses that pooled it.
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Who cites it
12 citing papers in PubMed, 3 syntheses or guidelines pooled it, 16 citations in OpenAlex.
- Monitoring COVID-19 vaccine effectiveness against COVID-19 hospitalisation and death using electronic health registries in ≥65 years old population in six European countries, October 2021 to November 2022.Influenza and other respiratory viruses · 2023Pooled it
- The Efficacy of SARS-CoV-2 Vaccination in the Elderly: A Systemic Review and Meta-analysis.Journal of general internal medicine · 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
- COVID-19 vaccine effectiveness in preventing severe outcomes and assessing the impact of prior SARS-CoV-2 infection among hospitalized adults in Albania, July 2022-July 2023.PLOS global public health · 2026Article
- Population-Based Analysis of Vaccination Status and Post-Vaccination Adverse Events in Adults Aged 55 and Older.Journal of clinical medicine · 2025Article
- Long term bivalent mRNA vaccine effectiveness against COVID-19 hospitalisations and deaths in Portugal: a cohort study based on electronic health records.BMC infectious diseases · 2025Article
- Impact of pharmaceutical and non-pharmaceutical interventions on COVID-19 in Tunisia.BMC public health · 2024Article
- Nonspecific Effects of the Bacillus Calmette-Guérin Vaccine in Portuguese Children Under 5 Years of Age: Protocol for a Population-Based Historical Birth Cohort Study.JMIR research protocols · 2024Article
- Computational design and evaluation of mRNA- and protein-based conjugate vaccines for influenza A and SARS-CoV-2 viruses.Journal, genetic engineering & biotechnology · 2023Article
- Vaccine-Induced or Hybrid Immunity and COVID-19-Associated Mortality During the Omicron Wave.Deutsches Arzteblatt international · 2023Article
- Comparative complete scheme and booster effectiveness of COVID-19 vaccines in preventing SARS-CoV-2 infections with SARS-CoV-2 Omicron (BA.1) and Delta (B.1.617.2) variants: A case-case study based on electronic health records.Influenza and other respiratory viruses · 2023Article
- High vaccine effectiveness against severe COVID-19 in the elderly in Finland before and after the emergence of Omicron.BMC infectious diseases · 2022Article
Corrections and comments
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Authors and funding
9 authors at 3 institutions in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundUsing data from electronic health registries, this study intended to estimate the COVID-19 vaccine effectiveness (VE) in the population aged 65 years and more, against symptomatic infection, COVID-19-related hospitalizations, and deaths, overall and by time since complete vaccination for the period February to September 2021.
methodsWe established a cohort of individuals aged 65 and more years old, resident in Portugal mainland, using the National Health Service User number to link eight electronic health registries. Outcomes included were symptomatic SARS-CoV-2 infections, COVID-19-related hospitalizations or deaths. The exposures of interest were the mRNA vaccines (Comirnaty or Spikevax) and the viral vector (Vaxzevria) vaccine. Complete schedule VE was estimated as one minus the confounder adjusted hazard ratio, for each outcome, estimated by time-dependent Cox regression with time-dependent vaccine exposure.
resultsFor the cohort of individuals aged 65-79 years, complete scheme VE against symptomatic infection varied 43 (95%CI: 37-49) (Vaxzevria) and 65 (95%CI: 62-68) (mRNA vaccines). This estimate was slightly lower in the ≥80 years cohort (53, 95%CI: 45-60) for mRNA vaccines). VE against COVID-19 hospitalization varied between 89% (95%CI: 52-94) for Vaxzevria and 95% (95%CI: 93-97) for mRNA vaccines for the cohort aged 65-79 years and was 76% (95%CI: 67-83) for mRNA vaccines in the ≥80 years cohort. High VE against COVID-19-related deaths was estimated, for both vaccine types, 95% and 81 (95%CI:76-86) for the 65-79 years and the ≥80 years cohort, respectively. We observed a significant waning of VE against symptomatic infection, with VE estimates reaching approximately 34% for both vaccine types and cohorts. Significant waning was observed for the COVID-19 hospitalizations in the ≥80 years cohort (decay from 83% (95%CI:68 to 91) 14-41 days to 63% (95%CI:37 to 78) 124 days after mRNA second dose). No significant waning effect was observed for COVID-19-related deaths in the period of follow-up of either cohort.
conclusionsIn a population with a high risk of SARS-CoV-2 complications, we observed higher overall VE estimates against more severe outcomes for both age cohorts when compared to symptomatic infections. Considering the analysis of VE according to time since complete vaccination, the results showed a waning effect for both age cohorts in symptomatic infection and COVID-19 hospitalization for the 80 and more years cohort.
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