Effectiveness of a Messenger RNA Vaccine Booster Dose Against Coronavirus Disease 2019 among US Healthcare Personnel, October 2021-July 2022


Ian D. Plumb, National Center for Immunization and Respiratory Diseases
Nicholas M. Mohr, University of Iowa
Melissa Hagen, National Center for Immunization and Respiratory Diseases
Ryan Wiegand, National Center for Immunization and Respiratory Diseases
Ghinwa Dumyati, University of Rochester Medical Center
Karisa K. Harland, University of Iowa
Anusha Krishnadasan, University of California, Los Angeles
Jade James Gist, National Center for Immunization and Respiratory Diseases
Glen Abedi, National Center for Immunization and Respiratory Diseases
Katherine E. Fleming-Dutra, National Center for Immunization and Respiratory Diseases
Nora Chea, Centers for Disease Control and Prevention
Jane Lee, California Emerging Infections Program
Devra Barter, Colorado Department of Public Health and Environment
Monica Brackney, Yale University
Scott K. Fridkin, Emory University School of Medicine
Lucy E. Wilson, University of Maryland, Baltimore County (UMBC)
Sara A. Lovett, Minnesota Department of Health
Valerie Ocampo, Oregon Health Authority
Erin C. Phipps, The University of New Mexico
Tiffanie M. Marcus, Vanderbilt University Medical Center
Howard A. Smithline
Peter C. Hou, Brigham and Women's Hospital
Lilly C. Lee, Jackson Memorial Hospital
Gregory J. Moran, David Geffen School of Medicine at UCLA
Elizabeth Krebs, Thomas Jefferson University Hospital
Mark T. Steele, University of Missouri-Kansas City
Stephen C. Lim, LSU Health Sciences Center - New OrleansFollow
Walter A. Schrading, The University of Alabama at Birmingham

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Open Forum Infectious Diseases


Background: Protection against symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (coronavirus disease 2019 [COVID-19]) can limit transmission and the risk of post-COVID conditions, and is particularly important among healthcare personnel. However, lower vaccine effectiveness (VE) has been reported since predominance of the Omicron SARS-CoV-2 variant. Methods: We evaluated the VE of a monovalent messenger RNA (mRNA) booster dose against COVID-19 from October 2021 to June 2022 among US healthcare personnel. After matching case-participants with COVID-19 to control-participants by 2-week period and site, we used conditional logistic regression to estimate the VE of a booster dose compared with completing only 2 mRNA doses >150 days previously, adjusted for multiple covariates. Results: Among 3279 case-participants and 3998 control-participants who had completed 2 mRNA doses, we estimated that the VE of a booster dose against COVID-19 declined from 86% (95% confidence interval, 81%-90%) during Delta predominance to 65% (58%-70%) during Omicron predominance. During Omicron predominance, VE declined from 73% (95% confidence interval, 67%-79%) 14-60 days after the booster dose, to 32% (4%-52%) ≥120 days after a booster dose. We found that VE was similar by age group, presence of underlying health conditions, and pregnancy status on the test date, as well as among immunocompromised participants. Conclusions: A booster dose conferred substantial protection against COVID-19 among healthcare personnel. However, VE was lower during Omicron predominance, and waning effectiveness was observed 4 months after booster dose receipt during this period. Our findings support recommendations to stay up to date on recommended doses of COVID-19 vaccines for all those eligible.

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