Royal College of Surgeons in Ireland
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Epidemiological assessment of SARS-COV-2 reinfection

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posted on 2022-09-07, 09:50 authored by Marwa AlMadhi, Adel Salman Alsayyad, Ronan ConroyRonan Conroy, Stephen AtkinStephen Atkin, Abdulla Al Awadhi, Jaffar A Al-Tawfiq, Manaf AlQahtaniManaf AlQahtani

Objectives: SARS-CoV-2 vaccination has shown reduced infection severity; however, the reinfection frequency amongst unvaccinated, partially vaccinated and fully vaccinated remains unclear. This study aims to elucidate the rates and associated factors for such occurrences.

Methods: This retrospective epidemiological report included 1362 COVID-19 reinfection cases in Bahrain between April 2020 and July 2021. We analysed differences in disease severity and reinfection characteristics between various vaccination statuses; fully vaccinated, interrupted vaccination, one vaccination dose, post-reinfection vaccination and unvaccinated.

Results: Reinfection cases increased from zero cases per month in April - June 2020 to a sharp peak of 579 reinfection cases in May 2021. Males constituted a significantly larger proportion of reinfections (60.3%, p<0.0001). Reinfection episodes were highest amongst the 30-39 years of age (29.7%). The least reinfection episodes occurred at 3-6 months after the first infection (20.6%) and most occurred ≥9 months after initial infection (46.4%). Most individuals were asymptomatic during both episodes (35.7%), Reinfection disease severity was mild, with vaccinated patients less likely to have symptomatic reinfection (OR 0·71, p=0·004). Only 6.6% reinfection cases required hospitalization. One death was recorded, corresponding to unvaccinated group.

Conclusion: Vaccine-induced immunity and prior infection with or without vaccination were effective in reducing reinfection disease severity.



The original article is available at

Published Citation

AlMadhi M, et al. Epidemiological assessment of SARS-COV-2 reinfection. Int J Infect Dis. 2022;123:9-16.

Publication Date

2 August 2022

PubMed ID



  • RCSI Bahrain
  • Public Health and Epidemiology


Elsevier B.V.


  • Published Version (Version of Record)