Protection Against the Omicron Variant Offered by Previous Severe Acute Respiratory Syndrome Coronavirus 2 Infection: A Retrospective Cohort Study

Michael B. Rothberg, Priscilla Kim, Nabin K. Shrestha, Lisa Kojima, Larisa G. Tereshchenko

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Background: Previous infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) provides strong protection against future infection. There is limited evidence on whether such protection extends to the Omicron variant. Methods: This retrospective cohort study included 635 341 patients tested for SARS-CoV-2 via polymerase chain reaction from 9 March 2020 to 1 March 2022. Patients were analyzed according to the wave in which they were initially infected. The primary outcome was reinfection during the Omicron period (20 December 2021-1 March 2022). We used a multivariable model to assess the effects of prior infection and vaccination on hospitalization. Results: Among the patients tested during the Omicron wave, 30.6% tested positive. Protection of prior infection against reinfection with Omicron ranged from 18.0% (95% confidence interval [CI], 13.0-22.7) for patients infected in wave 1 to 69.2% (95% CI, 63.4-74.1) for those infected in the Delta wave. In adjusted models, previous infection reduced hospitalization by 28.5% (95% CI, 19.1-36.7), whereas full vaccination plus a booster reduced it by 59.2% (95% CI, 54.8-63.1). Conclusions: Previous infection offered less protection against Omicron than was observed in past waves. Immunity against future waves will likely depend on the degree of similarity between variants.

Original languageEnglish (US)
Pages (from-to)E142-E147
JournalClinical Infectious Diseases
Volume76
Issue number3
DOIs
StatePublished - Feb 1 2023
Externally publishedYes

Keywords

  • COVID-19
  • Omicron
  • SARS-CoV-2
  • immunity
  • reinfection

ASJC Scopus subject areas

  • Microbiology (medical)
  • Infectious Diseases

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