A small study by researchers at Yale University has suggested a possible link between Covid vaccines and a rare set of ongoing symptoms in a limited number of people, prompting calls for further research.
Scientists described a condition they refer to as “post-vaccination syndrome.” Reported symptoms include brain fog, dizziness, ringing in the ears, and difficulty with physical exertion. The researchers stressed that the findings are early and based on a small group.
Blood tests from affected participants showed differences in some immune cells. In some cases, traces of Covid-related proteins were found in the blood long after vaccination. Researchers also observed signs that a common dormant virus, Epstein-Barr, may have been reactivated in some individuals.
The study involved a relatively small number of participants and has not yet been fully published or peer-reviewed. Experts involved say the findings do not prove that vaccines caused the symptoms, but suggest there may be biological patterns that need further investigation.
Large-scale studies continue to show that Covid vaccines are highly effective at preventing severe illness and death. Researchers say rare side effects can be difficult to identify and distinguish from unrelated health problems.
The team plans larger studies to better understand how common these symptoms may be and who could be most at risk. Independent experts agree more research is needed, while emphasizing the overall benefits of vaccination.