Cleveland Clinic Flu Shots Study Shows Vaccine INCREASED Risk of Getting the Flu

For many years, annual influenza vaccination has been widely promoted in the United States as a key public-health measure, often described as being supported by settled science. However, new research is raising fresh questions about how effective recent flu vaccines may be.

A study conducted by researchers at the Cleveland Clinic suggests that the 2024–2025 influenza vaccine did not provide protection against infection in the population studied and may have been associated with a higher risk of contracting the flu. The findings were posted as a preprint on the medical research server medRxiv, meaning they have not yet undergone peer review.

The study, led by Dr. Nabin K. Shrestha and colleagues from the Cleveland Clinic’s departments of Infectious Diseases, Infection Prevention, and Quantitative Health Sciences, followed 53,402 Cleveland Clinic employees in Ohio during the 2024–2025 respiratory virus season. The observation period began on October 1, 2024, and continued for 25 weeks, ending March 26, 2025.

By the end of the study period, 82.1% of participants (43,857 employees) had received a flu vaccine, most commonly a trivalent inactivated formulation. Over the course of the season, 1,079 employees—about 2.02% of the total cohort—tested positive for influenza, with nearly all cases (98.8%) identified as influenza A.

Using a time-dependent statistical model that accounted for when individuals received vaccination, the researchers calculated an overall vaccine effectiveness of –26.9% (95% confidence interval: –51.0% to –6.6%). This corresponded to a hazard ratio of 1.27, indicating that vaccinated participants had a higher measured risk of testing positive for influenza than those who were unvaccinated, after adjusting for age, sex, job category, and work location.

To address concerns about testing behavior, the researchers examined whether vaccinated employees were simply more likely to seek testing. While vaccinated individuals did undergo testing more frequently, the proportion of positive tests was similar between vaccinated and unvaccinated groups, suggesting the observed difference was not solely due to testing patterns.

A Simon–Makuch plot included in the analysis showed that infection rates were similar early in the season but increased more rapidly among vaccinated participants as influenza activity intensified. The study population had a mean age of 42, was approximately 75% female, and included about 20% clinical nurses.

In their conclusion, the authors wrote: “Among 53,402 working-aged Cleveland Clinic employees, we were unable to find a protective influence of influenza vaccination during the 2024–2025 respiratory viral season and found a significantly higher risk of influenza with vaccination when influenza activity was high.”

Because the study is a preprint and focused on a specific workforce population, the authors noted that further research and peer review are needed to better understand the findings and their broader implications.

Original Source