March 1, 2024

Latest booster reduces adults’ risk of moderate or severe COVID by more than half

Shaun Grannis and Brian Dixon

The most recent COVID-19 booster shot reduces adults’ risk of moderate or severe COVID by more than half, according to a new nationwide data study from September 2023 through January 2024, a period of JN.1 variant dominance.

The new study is one of the first to evaluate protection provided by the updated shot against COVID-19-associated emergency department and urgent care visits (markers for moderate disease) and against hospitalizations (a marker for severe disease), in individuals 18 and older, due to JN.1, the most recently predominant strain of COVID.

“Halving your risk of needing to visit an E.D. or urgent care center or to be treated in the hospital for COVID is significant,” said study co-author Shaun Grannis, M.D., M.S., Regenstrief Institute vice president for data and analytics and a professor at Indiana University School of Medicine. “As an informatician I want to highlight that the data we analyzed came from different populations and geographic locations, adults of all ages and the most recent COVID strain. This analysis strongly supports the benefit of getting a booster shot and as a clinician, I encourage my patients to do so.”

“These are encouraging findings,” said study co-author Brian Dixon, PhD, MPA, interim director of Regenstrief Institute’s Clem McDonald Center for Biomedical Informatics and professor at Indiana University Richard M. Fairbanks School of Public Health. “These estimates of vaccine effectiveness are what we would expect for an annual booster designed for an endemic virus that continues to evolve. We looked at a longer time period than similar studies in Europe, and we found good performance. Yet we do need to be alert to the presumed waning of the updated booster’s effectiveness, which we have seen in earlier COVID-19 vaccines. Americans should expect the CDC to recommend future boosters, likely on an annual schedule.”

These findings of protection against moderate and severe disease provided by the booster in this large study are consistent with those of an earlier, small scale study of individuals seen for testing at a pharmacy. That study did not include hospitalized patients.

The authors of the new study, co-authored by Drs. Grannis and Dixon, concluded, “In this analysis of updated COVID-19 VE [vaccine effectiveness], receipt of an updated COVID-19 vaccine dose provided protection against COVID-19-associated ED/UC [emergency department/critical care] visits and hospitalizations among immunocompetent adults. CDC will continue monitoring VE of updated COVID-19 vaccines. All adults should stay up to date with recommended COVID-19 vaccines, including receiving a dose of updated vaccine.”

Interim Effectiveness of Updated 2023–2024 (Monovalent XBB.1.5) COVID-19 Vaccines Against COVID-19–Associated Emergency Department and Urgent Care Encounters and Hospitalization Among Immunocompetent Adults Aged ≥18 Years — VISION and IVY Networks, September 2023–January 2024” is published in Morbidity and Mortality Report (MMWR). The study was funded by the CDC.

All authors and affiliations

Jennifer DeCuir, MD, PhD1; Amanda B. Payne, PhD1; Wesley H. Self, MD2; Elizabeth A.K. Rowley, DrPH3; Kristin Dascomb, MD, PhD4; Malini B. DeSilva, MD5; Stephanie A. Irving, MHS6; Shaun J. Grannis, MD7,8; Toan C. Ong, PhD9; Nicola P. Klein, MD, PhD10; Zachary A. Weber, PhD3; Sarah E. Reese, PhD3; Sarah W. Ball, ScD3; Michelle A. Barron9; Allison L. Naleway, PhD6; Brian E. Dixon, PhD8,39; Inih Essien, OD5; Daniel Bride, MS4; Karthik Natarajan, PhD11,12; Bruce Fireman10; Ami B. Shah, MPH1,13; Erica Okwuazi, MSc1,13; Ryan Wiegand, PhD1; Yuwei Zhu, MD2; Adam S. Lauring, MD, PhD14; Emily T. Martin, PhD14; Manjusha Gaglani, MBBS15,16; Ithan D. Peltan, MD17,18; Samuel M. Brown, MD17,18; Adit A. Ginde, MD9; Nicholas M. Mohr, MD19; Kevin W. Gibbs, MD20; David N. Hager, MD, PhD21; Matthew Prekker, MD22; Amira Mohamed, MD23; Vasisht Srinivasan, MD24; Jay S. Steingrub, MD25; Akram Khan, MD26; Laurence W. Busse, MD27; Abhijit Duggal, MD28; Jennifer G. Wilson, MD29; Steven Y. Chang, MD, PhD30; Christopher Mallow, MD31; Jennie H. Kwon, DO32; Matthew C. Exline, MD33; Cristie Columbus, MD15,34; Ivana A. Vaughn, PhD35; Basmah Safdar, MD36; Jarrod M. Mosier, MD37; Estelle S. Harris, MD18; Jonathan D. Casey, MD2; James D. Chappell, MD, PhD2; Carlos G. Grijalva, MD2; Sydney A. Swan2; Cassandra Johnson, MS2; Nathaniel M. Lewis, PhD38; Sascha Ellington, PhD38; Katherine Adams, MPH38; Mark W. Tenforde, MD, PhD38; Clinton R. Paden, PhD1; Fatimah S. Dawood, MD1; Katherine E. Fleming-Dutra, MD1; Diya Surie, MD1; Ruth Link-Gelles, PhD1; CDC COVID-19 Vaccine Effectiveness Collaborators

1Coronavirus and Other Respiratory Viruses Division, National Center for Immunization and Respiratory Diseases, CDC; 2Vanderbilt University Medical Center, Nashville, Tennessee; 3Westat, Rockville, Maryland; 4Division of Infectious Diseases and Clinical Epidemiology, Intermountain Healthcare, Salt Lake City, Utah; 5HealthPartners Institute, Minneapolis, Minnesota; 6Kaiser Permanente Center for Health Research, Portland, Oregon; 7Indiana University School of Medicine, Indianapolis, Indiana; 8Regenstrief Institute Center for Biomedical Informatics, Indianapolis, Indiana; 9University of Colorado School of Medicine, Aurora, Colorado; 10Kaiser Permanente Vaccine Study Center, Kaiser Permanente Northern California Division of Research, Oakland, California; 11Department of Biomedical Informatics, Columbia University Irving Medical Center, New York, New York; 12New York-Presbyterian Hospital, New York, New York; 13General Dynamics Information Technology, Falls Church, Virginia; 14University of Michigan, Ann Arbor, Michigan; 15Baylor Scott & White Health, Texas; 16Baylor College of Medicine, Temple, Texas; 17Intermountain Medical Center, Murray, Utah; 18University of Utah, Salt Lake City, Utah; 19University of Iowa, Iowa City, Iowa; 20Wake Forest School of Medicine, Winston-Salem, North Carolina; 21Johns Hopkins University School of Medicine, Baltimore, Maryland; 22Hennepin County Medical Center, Minneapolis, Minnesota; 23Montefiore Medical Center, Albert Einstein College of Medicine, New York, New York; 24University of Washington, Seattle, Washington; 25Baystate Medical Center, Springfield, Massachusetts; 26Oregon Health & Science University, Portland, Oregon; 27Emory University, Atlanta, Georgia; 28Cleveland Clinic, Cleveland, Ohio; 29Stanford University School of Medicine, Stanford, California; 30Ronald Reagan UCLA Medical Center, Los Angeles, California; 31University of Miami, Miami, Florida; 32Washington University in St. Louis, St. Louis, Missouri; 33The Ohio State University, Columbus, Ohio; 34Texas A&M University College of Medicine, Dallas, Texas; 35Henry Ford Health, Detroit, Michigan; 36Yale University School of Medicine, New Haven, Connecticut; 37University of Arizona, Tucson, Arizona; 38Influenza Division, National Center for Immunization and Respiratory Diseases, CDC; 39Richard M. Fairbanks School of Public Health at Indiana University-Indianapolis

About Shaun Grannis, M.D., M.S.
In addition to his role as the vice president for data and analytics at Regenstrief Institute, Shaun Grannis, M.D., M.S., holds the Regenstrief Chair in Medical Informatics and is a professor of family medicine at Indiana University School of Medicine.

Brian E. Dixon, PhD, MPA 
In addition to his role as the director of public health informatics at Regenstrief Institute and Indiana University Richard M. Fairbanks School of Public Health at Indiana University-Indianapolis, Brian E. Dixon, PhD, MPA, is the interim director and a research scientist with the Clem McDonald Center for Biomedical Informatics at Regenstrief Institute and an associate professor of epidemiology at Indiana University Fairbanks School of Public Health at IUPUI. He is also an affiliate scientist at the U.S. Department of Veterans Affairs Health Services Research and Development Center for Health Information and Communication, Richard L. Roudebush VA Medical Center.

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