Scientists Describe Rare Syndrome Following Covid Vaccinations

In a small study, patients with the syndrome were more likely to experience reactivation of Epstein-Barr virus and high levels of a coronavirus protein.


Like people with long Covid, some with post-vaccination syndrome showed reactivation of Epstein-Barr virus, which is linked to mononucleosis, multiple sclerosis and other conditions. Matthew Busch for The New York Times

By Apoorva Mandavilli
Published Feb. 19, 2025
Updated Feb. 21, 2025
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The Covid-19 vaccines were powerfully protective, preventing millions of deaths. But in a small number of people, the shots may have led to a constellation of side effects that includes fatigue, exercise intolerance, brain fog, tinnitus and dizziness, together referred to as “post-vaccination syndrome,” according to a small new study.

Some people with this syndrome appear to show distinct biological changes, the research found — among them differences in immune cells, reawakening of a dormant virus called Epstein-Barr, and the persistence of a coronavirus protein in their blood.

The study was posted online Wednesday and has not yet been published in a scientific journal. “I want to emphasize that this is still a work in progress,” said Akiko Iwasaki, an immunologist at Yale University who led the work.

“It’s not like this study determined what’s making people sick,” she said, “but it’s the first kind of glimpse at what may be going on within these people.”

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Apoorva Mandavilli reports on science and global health, with a focus on infectious diseases, pandemics and the public health agencies that try to manage them. More about Apoorva Mandavilli