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https://news.yale.edu/2025/02/19/immune-markers-post-vaccination-syndrome-indicate-future-research-directions
A small number of people report chronic symptoms after receiving COVID-19 shots. A new study provides clues for further research.
Feb 19, 2025
By
Mallory Locklear

COVID-19 vaccines have been instrumental in reducing the impact of the pandemic, preventing severe illness and death, and they appear to protect against long COVID. However, some individuals have reported chronic symptoms that developed soon after receiving a COVID-19 vaccine. This little-understood, persistent condition, referred to as post-vaccination syndrome (PVS), remains unrecognized by medical authorities, and little is known about its biological underpinnings.

In a new study, Yale researchers have taken initial steps to characterize this condition, uncovering potential immunological patterns that differentiate those with PVS from others. The findings are early and require further confirmation but may eventually guide strategies to help affected individuals.

“This work is still in its early stages, and we need to validate these findings,” said Akiko Iwasaki, Sterling Professor of Immunobiology at Yale School of Medicine (YSM) and co-senior author of the study published Feb. 19 as a preprint on medRxiv. “But this is giving us some hope that there may be something that we can use for diagnosis and treatment of PVS down the road.”

Some of the most common chronic symptoms of PVS include exercise intolerance, excessive fatigue, brain fog, insomnia, and dizziness. They develop shortly after vaccination, within a day or two, can become more severe in the days that follow, and persist over time. More studies are needed to understand the prevalence of PVS.

“It’s clear that some individuals are experiencing significant challenges after vaccination. Our responsibility as scientists and clinicians is to listen to their experiences, rigorously investigate the underlying causes, and seek ways to help,” said Harlan Krumholz, the Harold H. Hines, Jr. Professor of Medicine (Cardiology) at YSM and co-senior author of the study.

Data for the study came from Yale’s Listen to Immune, Symptom, and Treatment Experiences Now (LISTEN) Study, through which researchers aim to better understand long COVID and PVS. For the new study, researchers included data from 42 LISTEN participants who reported symptoms of PVS and 22 individuals who did not report any PVS symptoms after receiving a COVID-19 vaccination.

From participants’ blood samples, the researchers looked for immune features that were different between the two groups. They found several differences in immune cell populations; those with PVS had lower levels of effector CD4+ T cells and higher levels of TNF-alpha+ CD8 T cells — both are types of white blood cells — among other differences.
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@fourleaf It's taken 2 1/2 yrs, but this summer has been productive in solving my long covid. At this point, blood work appeared to show I've had an allergic reaction to the covid spike protein. My T-cells were the first clues providing answers to what was under attack. I have one final test pending to determine spike protein is seen by my auto-immune system overdrive because it decided it was an invasive 'fungi' . I feel what you reported about spike protein impacts to the brain is another clue for primary doctor to review. Hard to test brain tissue, but T Cell studies is the starting point. Thanks for the details.