ArticleCommunications medicine2025
Immune histories and natural infection protection during the omicron era.
Article in Communications medicine, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 2 papers.
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
2 citing papers in PubMed.
- Evaluating COVID-19 vaccine effectiveness across epidemiologic designs: test-negative case-control versus retrospective cohort analyses in a nationwide study.International journal of epidemiology · 2026Article
- Differences in the Clinical Course of COVID-19 in Patients Hospitalized in the 2023/2024 and 2024/2025 Seasons.Journal of clinical medicine · 2025Article
Corrections and comments
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Authors and funding
23 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundPast immunological events can either enhance or compromise an individual's future immune protection. This study investigated how different severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) natural infection histories before an omicron infection, with or without vaccination, influence protection against subsequent omicron reinfection.
methodsThree national, matched, retrospective cohort studies were conducted in Qatar from February 28, 2020, to August 12, 2024 to compare incidence of omicron reinfection between individuals with two omicron infections (omicron double-infection cohort) and those with one (omicron single-infection cohort); the omicron double-infection cohort with individuals who had a pre-omicron infection followed by an omicron reinfection (pre-omicron-omicron double-infection cohort); and the pre-omicron-omicron double-infection cohort with the omicron single-infection cohort.
resultsHere we show that, in the first study, comparing the omicron double-infection cohort to the omicron single-infection cohort, the adjusted hazard ratio (aHR) is 1.27 (95% CI: 1.13-1.43); 0.93 (95% CI: 0.68-1.28) for the unvaccinated and 1.34 (95% CI: 1.18-1.52) for the vaccinated. In the second study, comparing the omicron double-infection cohort to the pre-omicron-omicron double-infection cohort, the aHR is 1.37 (95% CI: 1.13-1.65); 1.12 (95% CI: 0.63-1.97) for the unvaccinated and 1.42 (95% CI: 1.16-1.74) for the vaccinated. In the third study, comparing the pre-omicron-omicron double-infection cohort to the omicron single-infection cohort, the aHR is 0.97 (95% CI: 0.92-1.03); 0.75 (95% CI: 0.66-0.85) for the unvaccinated and 1.03 (95% CI: 0.97-1.09) for the vaccinated.
conclusionsImmune history shapes protection against omicron reinfection, with pre-omicron-omicron immunity enhancing protection, while repeated similar exposures reduce protection against new variants.
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Registered trials
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