COVID-19 continues to be a public health threat.
According to the Centers for Disease Control and Prevention (CDC), between 380,000 and 540,000 people were hospitalized in the United States due to COVID-19 during the 2024-2025 season, and between 44,000 and 63,000 of them died.
That’s why researchers at Vanderbilt Health and around the country continue to evaluate the effectiveness of vaccines approved by the Food and Drug Administration to reduce the severity and lethality of respiratory infections caused by the ever-mutating SARS-CoV-2 virus.
The latest case-control study found that adults who received the 2024-2025 COVID-19 vaccine and were not immunosuppressed were 40% less likely to be hospitalized with COVID-19-related illness, and 79% less likely to require invasive mechanical ventilation (IMV) support — a ventilator — or die.
“Our finding of higher vaccine effectiveness against COVID-19–associated IMV or death shows the importance of recent vaccination to prevent the most severe outcomes following infection,” the researchers concluded. Timely estimates of vaccine effectiveness are critical, as COVID-19 vaccines must be frequently updated to cover new strains of the virus.
The study was conducted by a multi-center collaboration of 26 hospitals in 20 states called the Investigating Respiratory Viruses in the Acutely Ill (IVY) Network. Results were reported Feb. 3 in the journal JAMA Network Open.
Vanderbilt Health is the network’s coordinating center. Wesley Self, MD, MPH, Senior Vice President for Clinical Research and director of the Vanderbilt Institute for Clinical and Translational Research, is the IVY Network principal investigator.
“A vaccine’s ability to prevent critical illness and death is one of the key features we evaluate to understand the effectiveness of that vaccine,” said Self, who is also a professor of Emergency Medicine and holds the endowed Directorship in Emergency Care Research. “Despite evolution of the virus, COVID-19 vaccines administered in the U.S. last year were highly effective at preventing critical illness and death.”
The study included 8,493 patients over age 18 who were admitted to IVY Network hospitals with acute respiratory illness between Sept.1, 2024 and April 30, 2025. Of these, 1,888 had confirmed COVID-19.
Among patients with COVID-19 whose immune systems were not suppressed by, for example, drugs used to treat cancer or prevent transplant rejection, the 2024-2025 COVID-19 vaccine provided protection against multiple strains of SARS-CoV-2 that circulated during the 2024-2025 season.
In addition to Self, co-authors from Vanderbilt Health were Adrienne Baughman, CCRP, Afan Cornelison, MPH, Paul Blair, MD, MHS, Cassandra Johnson, MS, Todd Rice, MD, MSc, Carlos Grijalva, MD, MPH, H. Keipp Talbot, MD, MPH, Jonathan Casey, MD, MSCI, Natasha Halasa, MD, MPH, James Chappell, MD, PhD, and Yuwei Zhu, MD, MS.
Findings from the study, which was supported by the CDC, align with previously published preliminary estimates of vaccine effectiveness. Additional information on Staying Up to Date with COVID-19 Vaccines can be found on the CDC website.
