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. 2023 Jun 15;227(12):1348-1363.
doi: 10.1093/infdis/jiad040.

Protection From COVID-19 mRNA Vaccination and Prior SARS-CoV-2 Infection Against COVID-19-Associated Encounters in Adults During Delta and Omicron Predominance

Catherine H Bozio  1 , Kristen A Butterfield  2 , Melissa Briggs Hagen  1 , Shaun Grannis  3   4 , Paul Drawz  5 , Emily Hartmann  6 , Toan C Ong  7 , Bruce Fireman  8 , Karthik Natarajan  9   10 , Kristin Dascomb  11 , Manjusha Gaglani  12   13 , Malini B DeSilva  14 , Duck-Hye Yang  2 , Claire M Midgley  1 , Brian E Dixon  3   15 , Allison L Naleway  16 , Nancy Grisel  11 , I Chia Liao  12 , Sarah E Reese  2 , William F Fadel  3   15 , Stephanie A Irving  16 , Ned Lewis  8 , Julie Arndorfer  11 , Kempapura Murthy  12 , John Riddles  2 , Nimish R Valvi  3 , Mufaddal Mamawala  12 , Peter J Embi  3 , Mark G Thompson  1 , Edward Stenehjem  11
Affiliations

Protection From COVID-19 mRNA Vaccination and Prior SARS-CoV-2 Infection Against COVID-19-Associated Encounters in Adults During Delta and Omicron Predominance

Catherine H Bozio et al. J Infect Dis. .

Abstract

Background: Data assessing protection conferred from COVID-19 mRNA vaccination and/or prior SARS-CoV-2 infection during Delta and Omicron predominance periods in the United States are limited.

Methods: This cohort study included persons ≥18 years who had ≥1 health care encounter across 4 health systems and had been tested for SARS-CoV-2 before 26 August 2021. COVID-19 mRNA vaccination and prior SARS-CoV-2 infection defined the exposure. Cox regression estimated hazard ratios (HRs) for the Delta and Omicron periods; protection was calculated as (1-HR)×100%.

Results: Compared to unvaccinated and previously uninfected persons, during Delta predominance, protection against COVID-19-associated hospitalizations was high for those 2- or 3-dose vaccinated and previously infected, 3-dose vaccinated alone, and prior infection alone (range, 91%-97%, with overlapping 95% confidence intervals [CIs]); during Omicron predominance, estimates were lower (range, 77%-90%). Protection against COVID-19-associated emergency department/urgent care (ED/UC) encounters during Delta predominance was high for those exposure groups (range, 86%-93%); during Omicron predominance, protection remained high for those 3-dose vaccinated with or without a prior infection (76%; 95% CI = 67%-83% and 71%; 95% CI = 67%-73%, respectively).

Conclusions: COVID-19 mRNA vaccination and/or prior SARS-CoV-2 infection provided protection against COVID-19-associated hospitalizations and ED/UC encounters regardless of variant. Staying up-to-date with COVID-19 vaccination still provides protection against severe COVID-19 disease, regardless of prior infection.

Keywords: COVID-19 vaccination; COVID-19–associated hospitalizations; Omicron variant; prior SARS-CoV-2 infection; protection.

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Conflict of interest statement

Potential conflicts of interest. S. A. I., M. G., K. M., and B. E. D. report institutional support from Westat. A. L. N. reports institutional support from Pfizer for a study of meningococcal B vaccine safety during pregnancy and from Vir Biotechnology for an influenza study, unrelated to the current work. K. M. reports institutional support from CDC for 2 influenza studies, unrelated to the current work. M. G. reports institutional support from CDC for 2 influenza studies and 2 COVID-19 studies, all unrelated to the current work. B. E. D. reports support from US National Institutes of Health, CDC, Agency for Healthcare Research and Quality, and Department of Veterans Affairs related to use and evaluation of health information exchange technologies; royalties from Elsevier and Springer Nature for books; and consulting fees from Merck and Co. for advisory panel on HPV vaccination. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

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