## Flu Vaccine Effectiveness Questioned in New Study
Despite annual recommendations from the Centers for Disease Control and Prevention that all Americans 6 months and older receive a flu vaccine, a recent study is raising questions about its protective capabilities.
A preprint study released this week on MedRxiv.org examined data from the 2024-2025 influenza season and found an unexpected association between vaccination and infection rates among employees of the Cleveland Clinic in northern Ohio.
Key Findings: A Potential Increase in Infection Risk
The study analyzed information for over 53,400 Cleveland Clinic employees across a 25-week period. Researchers observed that those who received the influenza vaccine experienced a 27% increase in their risk of contracting the flu compared to unvaccinated individuals.
“This study found that influenza vaccination of working-aged adults was associated with a higher risk of influenza during the 2024-2025 respiratory viral season, suggesting that the vaccine has not been effective in preventing influenza this season,” researchers stated.
It’s important to note that this study is currently in the preprint stage and hasn’t undergone peer review.
Limitations and Considerations
The researchers acknowledged several limitations within their analysis, including:
- Nearly all employees included (99%) received the trivalent inactivated influenza vaccine.
- It’s possible that different flu vaccines might offer greater protection.
- Home testing practices could have impacted infection reporting accuracy.
- The study did not assess hospitalizations, deaths, or severity of illness linked to the flu.
- The sample primarily consisted of healthy, employed individuals, limiting generalizability.
Expert Opinions and Context
Dr. Marc Siegel, a clinical professor of medicine at NYU Langone Health, described the study’s results as “misleading.” He emphasized that the study is observational and doesn’t prove a lack of vaccine effectiveness.
“The biggest bias I see is that it is comparing vaccinated healthcare workers… with general population trends,” Dr. Siegel explained. “Healthcare workers are more likely to be exposed to flu in their profession, so we would expect the infection rate to be higher, whether vaccinated or not.”
Dr. Siegel also pointed out that the flu vaccine’s primary goal is to reduce disease severity, rather than prevent all infections.
Further Scrutiny and Future Research
Dr. Jacob Glanville, CEO of Centivax, a biotechnology company, stressed the importance of peer review before drawing conclusions from the study. He highlighted the need to rule out potential biases in reporting among unvaccinated employees.
Dr. Mike Sevilla, a family physician, agreed that this year’s vaccine appears less effective than usual, noting that he observed increased flu cases in his practice, although they weren’t typically severe. He emphasized the value of vaccination in mitigating illness severity, even if it doesn’t prevent infection entirely.
“I still tell my patients that a benefit from receiving the flu vaccine is that even though you may get the flu, your case may not be as severe as those who did not receive the flu vaccine,” he stated.
