How do COVID-19–associated hospitalization rates compare among adults who are unvaccinated and vaccinated, and what are the risk factors for hospitalization for COVID-19 among vaccinated persons?
In this cross-sectional study of US adults hospitalized with COVID-19 during January 2022 to April 2022 (during Omicron variant predominance), COVID-19-associated hospitalization rates were 10.5 times higher in unvaccinated persons and 2.5 times higher in vaccinated persons with no booster dose, respectively, compared with those who had received a booster dose. Compared with unvaccinated hospitalized persons, vaccinated hospitalized persons were more likely to be older and have more underlying medical conditions.
The study results suggest that COVID-19 vaccines are strongly associated with prevention of serious COVID-19 illness.
Understanding risk factors for hospitalization in vaccinated persons and the association of COVID-19 vaccines with hospitalization rates is critical for public health efforts to control COVID-19.
To determine characteristics of COVID-19–associated hospitalizations among vaccinated persons and comparative hospitalization rates in unvaccinated and vaccinated persons.
Design, Setting, and Participants
From January 1, 2021, to April 30, 2022, patients 18 years or older with laboratory-confirmed SARS-CoV-2 infection were identified from more than 250 hospitals in the population-based COVID-19–Associated Hospitalization Surveillance Network. State immunization information system data were linked to cases, and the vaccination coverage data of the defined catchment population were used to compare hospitalization rates in unvaccinated and vaccinated individuals. Vaccinated and unvaccinated patient characteristics were compared in a representative sample with detailed medical record review; unweighted case counts and weighted percentages were calculated.
Laboratory-confirmed COVID-19–associated hospitalization, defined as a positive SARS-CoV-2 test result within 14 days before or during hospitalization.
Main Outcomes and Measures
COVID-19–associated hospitalization rates among vaccinated vs unvaccinated persons and factors associated with COVID-19–associated hospitalization in vaccinated persons were assessed.
Using representative data from 192 509 hospitalizations (see Table 1 for demographic information), monthly COVID-19–associated hospitalization rates ranged from 3.5 times to 17.7 times higher in unvaccinated persons than vaccinated persons regardless of booster dose status. From January to April 2022, when the Omicron variant was predominant, hospitalization rates were 10.5 times higher in unvaccinated persons and 2.5 times higher in vaccinated persons with no booster dose, respectively, compared with those who had received a booster dose. Among sampled cases, vaccinated hospitalized patients with COVID-19 were older than those who were unvaccinated (median [IQR] age, 70 [58-80] years vs 58 [46-70] years, respectively; P < .001) and more likely to have 3 or more underlying medical conditions (1926 [77.8%] vs 4124 [51.6%], respectively; P < .001).
Conclusions and Relevance
In this cross-sectional study of US adults hospitalized with COVID-19, unvaccinated adults were more likely to be hospitalized compared with vaccinated adults; hospitalization rates were lowest in those who had received a booster dose. Hospitalized vaccinated persons were older and more likely to have 3 or more underlying medical conditions and be long-term care facility residents compared with hospitalized unvaccinated persons. The study results suggest that clinicians and public health practitioners should continue to promote vaccination with all recommended doses for eligible persons.
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CME Disclosure Statement: Unless noted, all individuals in control of content reported no relevant financial relationships. If applicable, all relevant financial relationships have been mitigated.
Accepted for Publication: August 4, 2022.
Published Online: September 8, 2022. doi:10.1001/jamainternmed.2022.4299
Corresponding Author: Fiona Havers, MD, MHS, 1600 Clifton Rd, US Centers for Disease Control and PrevenMS H24-6, Atlanta, GA 30329 (firstname.lastname@example.org).
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2022 Havers FP et al. JAMA Internal Medicine.
Author Contributions: Dr Havers had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Havers, Pham, Milucky, Meek, Lynfield, Como-Sabetti, Talbot.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Havers, Pham, Billing, Murthy, McMorrow.
Critical revision of the manuscript for important intellectual content: Pham, Taylor, Whitaker, Patel, Anglin, Kambhampati, Milucky, Zell, Moline, Chai, Daily Kirley, Alden, Armistead, Yousey-Hindes, Meek, Openo, Anderson, Reeg, Kohrman, Lynfield, Como-Sabetti, Davis, Cline, Muse, Barney, Bushey, Felsen, Shiltz, Sutton, Abdullah, Talbot, Schaffner, Hill, George, Hall, Bialek, Murthy, Patel Murthy, McMorrow.
Statistical analysis: Pham, Whitaker, Patel, Milucky, Moline, Como-Sabetti.
Obtained funding: Havers, Meek, Schaffner, McMorrow.
Administrative, technical, or material support: Havers, Pham, Taylor, Anglin, Kambhampati, Milucky, Zell, Alden, Meek, Openo, Anderson, Lynfield, Como-Sabetti, Barney, Billing, Sutton, Schaffner, Hill, Hall, Murthy, Patel Murthy, McMorrow.
Supervision: Havers, Meek, Anderson, Como-Sabetti, Sutton, Talbot, Schaffner, Hill, Hall, Bialek, McMorrow.
Other - data collection and reporting: Bushey.
Other - contribution of site specific data collection information: Daily Kirley.
Other - reviewed the draft and provided comments: Abdullah.
Conflict of Interest Disclosures: Drs Yousey-Hindes, Lynfield, Sutton, Talbot, and Meek reported grants from US Centers for Disease Control and Prevention (CDC) during the conduct of the study. Dr Anderson reported grants from Pfizer, Sanofi, GSK, Janssen, MedImmune, Regeneron, PaxVax, Micron, and Merck as well as personal fees from Moderna, Pfizer, Sanofi, GSK, Janssen, Medscape, Kentucky BioProcessing Inc, and WCG and ACI outside the submitted work; additionally, his institution has also received funding from the National Institutes of Health to conduct clinical trials of COVID-19 vaccines. Drs Reeg and Kohrman reported grants from the Michigan Department of Health and Human Services during the conduct of the study. Drs Billing and Shiltz reported grants from the Council of State and Territorial Epidemiologists (CTSTE) and the CDC Dr Schaffner reported grants from CDC during the conduct of the study as well as personal fees from VBI Vaccines outside the submitted work. Drs Hill and George reported grants from CSTE during the conduct of the study. No other disclosures were reported.
Funding/Support: This work was supported by the CDC through an Emerging Infections Program cooperative agreement (grant CK17-1701) and through a CSTE cooperative agreement (grant NU38OT000297-02-00).
Role of the Funder/Sponsor: CDC was involved with the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the CDC.
Additional Contributions: The following people were involved in the collection and management of study data and received funding from CDC for these activities: Roxanne Archer, MPH, Susan Brooks, MPH, Monica Napoles, BS, Jeremy Roland, MPH, Tiffany Tsukuda, MPH, California Emerging Infections Program; Arthur Reingold, MD, University of California, Berkeley; Rachel Herlihy, MD, MPH, Breanna Kawasaki, MPH, Sarah McLafferty, MPH, Millen Tsegaye, MHA Jordan Surgnier, MPH, Colorado Department of Public Health and Environment; Ann Basting, BS, Tessa Carter, MPH, Maria Correa, MPH, Daewi Kim, MBS, Carol Lyons, MPH, Amber Maslar, MPA, Julie Plano, MS, Hazhia Sorosindi, BS, Connecticut Emerging Infections Program, Yale School of Public Health; Katelyn Ward, MPH, Georgia Emerging Infections Program, Georgia Department of Public Health, Division of Infectious Diseases, Emory University School of Medicine; Marina Bruck, MPH, Rayna Ceasar, BS, Gracie Chambers, BS, Taylor Eisenstein, MPH, Emily Fawcett, MPH, Asmith Joseph, MPH, Grayson Kallas, MPH, Stephanie Lehman, BSN, RN, Jana Manning, MPH, Hope Wilson, MPH, Johanna Hernandez, MPH, Sabrina Hendrick, MPH, Annabel Patterson, MPH, Allison Roebling, DVM, MPH, Chandler Surell, MPH, Georgia Emerging Infections Program, Georgia Department of Public Health, Veterans Affairs Medical Center, Foundation for Atlanta Veterans Education and Research; Sue Kim, MPH, Val Tellez Nunez, MPH, Chloe Brown, MPH, Jim Collins, MPH, Justin Henderson, MPH, Shannon Johnson, MPH, Lauren Leegwater, MPH, Sierra Peguies-Khan, MPH, Michigan Department of Health and Human Services; Stephanie Meyer, MPH, Keeley Morris, MPH, Aaron Bieringer, BS, Erica Bye, MPH, Richard Danila, PhD, MPH, Corinne Holtzman, MPH, Sydney Kuramoto, MPH, Miriam Muscoplat, MPH, Kayla Bilski, MPH, Amanda Markelz, MPH, Margaret Roddy, MPH, Amy Saupe, MPH, Kristin Sweet, PhD, MPH, Minnesota Department of Health; Marianne Murphy, Murtada Khalifa, MBBS, Yassir Talha, MBBS, CDC Foundation, New Mexico Department of Health; Florent Nkouaga, MA, Melissa Judson, Sunshine Martinez, Jasmyn Sanchez, Susan L. Ropp, PhD, Chad Smelser, MD, Daniel M. Sosin, MD, MPH, New Mexico Department of Health; Dominic Rudin, BS, Kathy M. Angeles, MPH, Melissa Christian, MPH, Nancy Eisenberg, MPH, Emily B. Hancock, MS, Sarah A. Khanlian, MPH, Sarah Lathrop, DVM, PhD, Wickliffe Omondi, MPH, Mayvilynne Poblete, MA, MPH, Yadira Salazar-Sánchez, MPH, Sarah Shrum Davis, MPH, Chelsea McMullen, MSc-GH, New Mexico Emerging Infections Program; Nancy Spina, MPH, Kerianne Engesser, MPH, Suzanne McGuire, MPH, Adam Rowe, BA, New York State Department of Health; Nancy M. Bennett, MD, MS, Virginia Cafferky, BS, Maria Gaitán, BS, Christine Long, MPH, Thomas Peer, MPH, Kevin Popham, MPH, University of Rochester School of Medicine and Dentistry; Kylie Seeley, MD, MPH, Oregon Health & Science University School of Medicine; Sam Hawkins, MPH, Ama Owusu-Dommey, MPH, Emily Youngers, MPH, Breanna McArdle, MPH, Public Health Division; Oregon Health Authority; Tiffanie Markus, PhD, Kathy Billings, MPH, Katie Dyer, Anise Elie, MPH, BSN, RN, Karen Leib, BSN, RN, Terri McMinn, Danielle Ndi, MPH, Manideepthi Pemmaraju, MBBS, MPH, John Ujwok, MPH, Vanderbilt University Medical Center; Amanda Carter, BS, Ryan Chatelain, MPH, Andrew Haraghey, BS, Laine McCullough, MPH, Jacob Ortega, MPH, Andrea Price, LPN, Tyler Riedesel, MPH, Caitlin Shaw, BS, Melanie Crossland, MPH, Ashley Swain, Salt Lake County Health Department; Keegan McCaffrey, BS, Utah Department of Health; Kelly Oakeson, PhD, and Alessandro Rossi, PhD, Utah Public Health Laboratory. In addition, Li Deng, PhD, CDC, contributed statistical advice, and Hannah E. Fast, MPH, CDC, assisted with vaccination coverage data. Neither received additional funding for these activities.
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