Abstract
Background
Previous infection with 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 (PCR) from 09 March 2020 to 01 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, to 01 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), while full vaccination plus a booster reduced it by 59.2% (95% CI, 54.8-63.1).
Keywords: COVID-19, SARS-CoV-2, Omicron, reinfection, immunity
Contributor Information
Michael B Rothberg, Center for Value-Based Care Research, Cleveland Clinic, Cleveland, Ohio, USA.
Priscilla Kim, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, USA.
Nabin K Shrestha, Department of Infectious Disease, Cleveland Clinic, Cleveland, Ohio, USA.
Lisa Kojima, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, USA.
Larisa G Tereshchenko, Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, Ohio, USA.
Supplementary Material
Associated Data
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