Updated COVID-19 vaccines have been shown to be effective against severe forms of the disease

A new interstate study conducted by the Centers for Disease Control and Prevention (CDC) VISION network—including the Regenstrief Institute—has provided the most comprehensive assessment to date of the effectiveness of COVID-19 vaccines in 2023 -2024 vaccines among the US adult population during the waves of the Omicron XBB and JN.1 subvariants.

The data show that receiving updated COVID-19 vaccines remains critical, especially for older adults and those at increased risk of severe outcomes, and highlight the additional protection provided by updated COVID-19 vaccines beyond previous infection or vaccination. Although protection against mild and moderate disease declined over time, the vaccine continued to provide robust protection against critical disease throughout the study period.

Partners in this study, in addition to the CDC and Regenstrief, include Kaiser Permanente Northwest, the University of Colorado, Intermountain Health, HealthPartners, and Kaiser Permanente Northern California.

These results are encouraging and informative for patient care. This study demonstrates that updated COVID-19 vaccines continue to provide significant protection against severe outcomes such as hospitalization and critical illness, especially in the first months after vaccination. These results reinforce the importance of timely vaccination with recommended vaccines, especially for older and most vulnerable patients, as the virus continues to evolve.

The study, led by Shaun Grannis, MD, MS, vice president of data and analytics at Regenstrief and professor at the Indiana University School of Medicine, covered more than 345,000 emergency department (ED) visits urgent care centers and more than 111,000 adult hospitalizations in the United States across 230 hospitals and 362 EPs and urgent care centers.

Key findings

• Updated vaccines reduced the risk of visiting emergency departments and urgent care centers for COVID-19 by 24%, hospitalizations by 29%, and critical illness (hospitalization in the intensive care unit or death in the hospital) by 48% during the first 7–299 days after vaccination.
• Maximum protection against all measured outcomes of COVID-19 was observed during the first two months after vaccination, with a 68% reduction in severe critical illness.
• Vaccine effectiveness declined over time, especially six or more months after vaccination.

The study was conducted through the CDC’s VISION network.

VISION researchers evaluated electronic medical record data integrated with laboratory and vaccination records for the period from September 21, 2023, to August 22, 2024. The study focused on adults aged 18 years and older and aimed to examine outcomes among those who received and did not receive the 2023-2024 XBB.1.5 monovalent COVID-19 vaccines. The study covered periods when both Omicron variants, XBB and JN.1, were prevalent.

“This study provides encouraging news for public health,” said study co-author Brian Dixon, PhD, MPA, director of the Regenstrief Center for Biomedical Informatics and professor at the Indianapolis School of Public Health. “Our results show that updated COVID-19 vaccines continue to provide protection against severe disease and hospitalization. Effective vaccines remain an important tool for maintaining public health and reducing the costs associated with COVID-19 infection by preventing hospitalizations and emergency department visits.”

The study results underscore the importance of following CDC recommendations for updated COVID-19 vaccination, especially in light of waning immunity and the ongoing evolution of the virus. Protection was particularly significant for adults aged 65 and older, confirming current public health recommendations that call for timely vaccination and additional doses for high-risk groups.

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Published: 27.06.2025

Updated: 27.06.2025

Medical author, Medical editor:

Stepan Yuk

Medical expert:

PhD. Olexandr Voznyak