Emergency department study shows major gaps in flu vaccination

A University of California, Riverside-led study of more than 3,200 emergency department (ED) patients across the United States found that while awareness of influenza vaccination is widespread, most adults seen in EDs are not up to date on their annual flu vaccine.

The findings, published in the Journal of Emergency Medicine, suggest that EDs could play an important role in increasing vaccine coverage, particularly among medically underserved populations.

Led by Dr. Robert Rodriguez, a professor of medicine in the UCR School of Medicine, the researchers surveyed 3,285 adult patients at 10 emergency departments in eight U.S. cities between April and December 2024. Nearly all participants (96%) had heard of the influenza vaccine, and 77.6% reported receiving a flu vaccine at some point in their lives. However, 58.4% had not received a flu vaccine within the past year and were therefore not up to date with current recommendations.

The study also identified significant disparities in vaccination status. Patients without a primary care provider were more than twice as likely to be behind on influenza vaccination, with lower vaccination rates also seen in patients lacking insurance and African American patients.

Among participants who were not up to date on their flu vaccination, 37% said they would accept a flu shot if it were offered during their emergency department visit.

"Emergency departments are often the only point of contact with the health care system for many patients," said coauthor Dr. Rajesh Gulati, a professor of medicine in the UCR School of Medicine. "Our findings show that there is a substantial opportunity to reach people who may not have access to primary care and help close important gaps in influenza vaccination coverage."

Influenza remains a major global public health threat, contributing to an estimated 650,000 deaths worldwide each year. Despite longstanding recommendations for annual vaccination, fewer than half of U.S. adults received a flu vaccine during the 2023-2024 season.

The researchers found that lack of primary care access was the strongest predictor of being behind on influenza vaccination. More than one in five study participants reported not having a primary care provider.

"The message from this study is clear: many patients who are either unaware of or not receiving preventive care elsewhere are willing to be vaccinated when given the opportunity," said Sanya Dhama, first author of the paper and a medical student at UCR. "Emergency departments can serve as a critical public health safety net - not only for acute care, but also for preventive services such as influenza vaccination."

Among patients who declined vaccination in the emergency department, the most common concerns were fear of vaccine side effects, a desire for more information about vaccines and influenza, and feeling too ill at the time of the visit.

"These findings suggest that educational messaging and targeted outreach could further improve acceptance," Rodriguez said.

The cross-sectional study was conducted at EDs in Chicago, Detroit, Durham, Philadelphia, Fresno, Los Angeles, San Francisco, and Sylmar. The researchers surveyed adult patients regarding their knowledge of influenza vaccination, vaccination status, willingness to receive a flu shot in the emergency department, and reasons for vaccine acceptance or refusal.

"Emergency departments represent an underutilized venue for influenza vaccination surveillance, education, and vaccine delivery," Rodriguez said. "Expanding ED-based vaccination programs could help reduce influenza-related illness, hospitalization, and death, particularly among populations with limited access to routine health care."

The study was supported in part by the National Institute of Allergy and Infectious Diseases.

Rodriguez, Gulati, and Dhama were joined in the study by Shaokui Ge at UCR; Dr. Jesus Torres at UCLA; Dr. Brian Chinnock at UCSF Fresno; Dr. Michael Gottlieb at Rush University Medical Center, Illinois; Dr. Vijaya Arun Kumar at Wayne State University, Michigan; Dr. Kristin L. Rising and Dr. Efrat Rosenzweig Kean at the Thomas Jefferson University Hospital, Pennsylvania; Dr. Stephanie Eucker, at the Duke University School of Medicine, North Carolina; Dr. Melanie F. Molina at UC San Francisco.

The title of the paper is "Up to Date Status and Acceptance of the Influenza Vaccine among a National Sample of Emergency Department Patients."

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