A new multi-state study led by the Centers for Disease Control and Prevention's (CDC) VISION Network – including Regenstrief Institute – has provided the most comprehensive assessment to date of the effectiveness of 2023-2024 COVID-19 vaccines among adults in the U.S. during the XBB and JN.1 Omicron subvariant waves.
Data suggest that receiving updated COVID-19 vaccines remains crucial, especially for older adults and those at increased risk for severe outcomes, and underscores the additional protection provided by the updated COVID-19 vaccines, above and beyond previous infection or vaccination. While protection against mild and moderate illness decreased over time, the vaccine continued to offer strong defense against critical illness throughout the study period.
Partners for this study, in addition to the CDC and Regenstrief, include Kaiser Permanente Northwest, University of Colorado, Intermountain Health, HealthPartners and Kaiser Permanente Northern California.
"These results are both reassuring and instructive for patient care," said study co-author Shaun Grannis, M.D., M.S., vice president for data and analytics at Regenstrief and a professor at the Indiana University School of Medicine. "This study demonstrates that the updated COVID-19 vaccines continue to offer significant protection against severe outcomes like hospitalization and critical illness, especially in the months immediately following vaccination. These findings reinforce the importance of staying up to date with recommended vaccines, particularly for our older and more vulnerable patients as the virus continues to evolve."
The study spanned more than 345,000 emergency department (ED)/urgent care encounters and more than 111,000 hospitalizations in adults in the U.S. across 230 hospitals and 362 E.D.s and urgent care centers.
Key Findings
- The updated vaccines reduced the risk of ED and urgent care visits related to COVID-19 by 24 percent, hospitalizations by 29 percent and critical illness (intensive care unit admission or in-hospital death) by 48 percent during the first seven to 299 days after vaccination.
- Maximum protection against all measured COVID-19 outcomes was observed during the first two months after vaccination, with severe case reduction of up to 68 percent against critical illness.
- Vaccine effectiveness (VE) waned over time, particularly beyond six months after vaccination.
The study was conducted through the CDC's VISION Network in collaboration with healthcare systems in Oregon and Washington (Kaiser Permanente Northwest), Colorado (University of Colorado), Utah (Intermountain Health), Indiana (Regenstrief Institute), Minnesota and Wisconsin (HealthPartners), and California (Kaiser Permanente Northern California). Regenstrief Institute contributes data and scientific expertise to the network, ensuring robust analysis across a broad range of medical facilities in urban and rural areas.
VISION investigators evaluated electronic health record data, integrated with laboratory and vaccination records, from September 21, 2023, to August 22, 2024. The research focused on adults aged 18 years and older, examining outcomes among those who did and did not receive the 2023-2024 monovalent XBB.1.5 COVID-19 vaccines. The study covered periods when both XBB and JN.1 Omicron variants were predominant.
"This study offers encouraging news for population health," said co-author Brian Dixon, PhD, MPA, director of the Regenstrief Center for Biomedical Informatics and a professor at IU Indianapolis Fairbanks School of Public Health. "Our findings show that the updated COVID-19 vaccines continue to provide protection against severe illness and hospitalization. Effective vaccines remain a critical tool in keeping communities healthy and reducing costs associated with COVID-19 infection by preventing hospitalizations and emergency department visits."
The findings highlight the importance of following CDC recommendations for updated COVID-19 vaccination, particularly in light of waning immunity and continuing virus evolution. Protection was especially significant for adults 65 and older, supporting current public health guidance that recommends timely vaccination and additional doses for high-risk groups.
The study, "Estimated 2023-2024 COVID-19 Vaccine Effectiveness in Adults," was funded by the CDC and is published in JAMA Network Open.
About the VISION Network
Established in 2019, the Virtual SARS-CoV-2, Influenza, and Other Respiratory Viruses Network (VISION) is a research collaboration among CDC, Westat and health systems nationwide. The network's integrated approach allows for real-time evaluation of vaccines and other preventive measures against respiratory illnesses, including RSV, COVID-19 and influenza.
CDC's VISION Network advances scientific knowledge on vaccine effectiveness by leveraging the power of integrated medical, laboratory and immunization data from leading health systems and public health institutes across the United States.
Authors and affiliations as listed in the publication
Ruth Link-Gelles, PhD; Elizabeth A. K. Rowley, DrPH; Stephanie A. Irving, MHS; Nicola P. Klein, MD, PhD; Shaun J. Grannis, MD; Toan C. Ong, PhD; Sarah W. Ball, ScD; Malini B. DeSilva, MD; Kristin Dascomb, MD, PhD; Allison L. Naleway, PhD; Padma Koppolu, MPH; Ousseny Zerbo, PhD; Bruce Fireman, PhD; John Hansen, MPH; Julius Timbol, MS; Lawrence Block, MPH; Brian E. Dixon, PhD; Thomas J. Duszynski, PhD; Katie S. Allen, BS; David Mayer, BS; Catia Chavez, MPH; Michelle Barron, MD; Sarah E. Reese, PhD; Sean Chickery, DHSc; Jonathan M. Davis, PhD; Allison Avrich Ciesla, PhD; Josephine Mak, MPH; Morgan Najdowski, MPH; Omobosola O. Akinsete, MD; Charlene E. McEvoy, MD; Inih J. Essien, OD; Tamara Sheffield, MD; Daniel Bride, MS; Julie Arndorfer, MPH; Joshua Van Otterloo, MSPH; Karthik Natarajan, PhD; Mark W. Tenforde, MD, PhD; Jennifer DeCuir, MD, PhD; Amanda B. Payne, PhD.
National Center for Immunizations and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia (Link-Gelles, Ciesla, Mak, Najdowski, Tenforde, DeCuir, Payne); Public Health Service Commissioned Corps, Rockville, Maryland (Link-Gelles, DeCuir); Westat, Rockville, Maryland (Rowley, Ball, Reese, Chickery, Davis); Kaiser Permanente Center for Health Research, Portland, Oregon (Irving, Naleway, Koppolu); Kaiser Permanente Vaccine Study Center, Kaiser Permanente Northern California Division of Research, Oakland (Klein, Zerbo, Fireman, Hansen, Timbol, Block); Indiana University School of Medicine, Indianapolis (Grannis); Regenstrief Institute Center for Biomedical Informatics, Indianapolis, Indiana (Grannis, Dixon, Duszynski, Allen); University of Colorado School of Medicine, Aurora (Ong, Mayer, Chavez, Barron); HealthPartners Institute, Minneapolis, Minnesota (DeSilva, Akinsete, McEvoy, Essien); Division of Infectious Diseases and Clinical Epidemiology, Intermountain Health, Salt Lake City, Utah (Dascomb, Sheffield, Bride, Arndorfer, Van Otterloo); Department of Health Policy and Management, Richard M Fairbanks School of Public Health, Indiana University, Indianapolis (Dixon, Allen); Department of Epidemiology, Richard M. Fairbanks School of Public Health, Indiana University, Indianapolis (Duszynski); Eagle Health Analytics, San Antonio, Texas (Ciesla, Najdowski); Department of Biomedical Informatics, Columbia University Irving Medical Center, New York, New York (Natarajan).
Funding/Support: This study was supported by the Centers for Disease Control and Prevention through contract 73D3012779 to Westat Inc. and contract 75D30123C17595 to Kaiser Foundation Hospitals.
Disclaimer: The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
Shaun Grannis, M.D., M.S.
Dr. Shaun Grannis is vice president of data and analytics at Regenstrief Institute, the Regenstrief Chair in Medical Informatics, and a professor of family medicine at the Indiana University School of Medicine.
Brian E. Dixon, PhD, MPA
In addition to his role as the director of public health informatics at the Regenstrief Institute and Indiana University Indianapolis Richard M. Fairbanks School of Public Health, Brian E. Dixon, PhD, MPA, is the director and a research scientist with the Clem McDonald Center for Biomedical Informatics at the Regenstrief Institute and a professor of health management and policy at the Fairbanks School. He is also an affiliate scientist at the U.S. Department of Veterans Affairs Health Systems Research and Development Center for Health Information and Communication, Richard L. Roudebush VA Medical Center.
