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Incidence, severity, risk factors and outcomes of SARS-CoV-2 reinfections during the Omicron period: a systematic review and meta-analysis

Kulkarni D 1 , Lee B 1 , Ismail NF 2 , Rahman AE 3 , Spinardi J 4 , Kyaw MH 4 Show all authors , Nair H 1

Affiliations 

  • 1 Centre for Global Health, Usher Institute, University of Edinburgh, Edinburgh, UK
  • 2 Communicable Disease Control Unit, Public Health Department, Johor Bahru, Johor State, Malaysia
  • 3 International Centre for Diarrhoeal Diseases Research, Dhaka, Bangladesh
  • 4 Pfizer, Vaccines, Emerging Markets, New York, New York, USA
J Glob Health, 2025 Feb 07;15:04032.
PMID: 39916552 DOI: 10.7189/jogh.15.04032

Abstract

BACKGROUND: Our previous systematic review estimated the cumulative incidence of SARS-CoV-2 reinfections as 1.16% (95% CI = 1.01-1.33%) during the pre-Omicron period. The Omicron variant that emerged in November 2021 was significantly genetically distinct from the previous SARS-CoV-2 variants and thus, more transmissible and posed an increased risk of SARS-CoV-2 reinfections in the population. We, therefore, conducted a fresh systematic review and meta-analysis to estimate the SARS-CoV-2 reinfection burden during the Omicron period.

METHODS: We searched CINAHL, Medline, Global Health, Embase, and WHO COVID-19 in October 2023 for studies reporting the SARS-CoV-2 reinfection incidence during the Omicron period. The quality of the included studies was assessed using the Joanna Briggs Institute checklists. Random effects meta-analyses were conducted to estimate the incidence, and requirement of hospitalisation of SARS-CoV-2 reinfections. Symptomatic severity of reinfections and case fatality rates were analysed narratively.

RESULTS: Thirty-six studies were included. The reinfection cumulative incidence during the Omicron period was 3.35% (95% CI = 1.95-5.72%) based on data from 28 studies. The cumulative incidence was higher in 18-59-year-old adults (6.62% (95% CI = 3.22-13.12%)) compared to other age groups and in health care workers (9.88% (95% CI = 5.18-18.03%)) compared to the general population (2.48% (95% CI = 1.34-4.54%)). We estimated about 1.81% (95% CI = 0.18-15.87%) of the reinfected cases required hospitalisation based on limited and highly variable data.

CONCLUSIONS: There was an increased risk of reinfections during the Omicron period compared to the pre-Omicron period. The incidence was higher in 18-59-year-old adults and health care workers and generally less severe during the Omicron period. However, data were limited on disease severity and long-term outcomes.

REGISTRATION: PROSPERO: CRD42023482598.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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