New Delhi: For most people, COVID vaccines do their job without issue. But for a small group, something unusual happens. Symptoms such as extreme fatigue, brain fog, dizziness, and insomnia can last for months, even years. Scientists at Yale University are now digging into why.
They’ve labelled the condition “post-vaccination syndrome” (PVS) and are investigating its potential causes. Their early findings reveal unique immune system patterns in those affected—offering a first step toward understanding, diagnosing, and eventually treating the condition.
“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. “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.”
What the Study Found
Yale researchers examined blood samples from 42 people suffering from PVS and compared them with 22 people who had been vaccinated without issue. Their analysis found two key differences in those with symptoms:
Lower levels of two types of white blood cells
Reduced antibodies against the SARS-CoV-2 spike protein (in those who had never had COVID and received fewer vaccine doses)
A portion of those with PVS also had higher levels of the spike protein, the same viral component that helps COVID infect cells. This phenomenon has been previously linked to an increased risk of long COVID.
“We don’t know if the level of spike protein is causing the chronic symptoms, because there were other participants with PVS who didn’t have any measurable spike protein—but it could be one mechanism underlying this syndrome,” Iwasaki explained.
Other possible contributing factors include autoimmune responses, tissue damage, and the reactivation of Epstein-Barr virus (EBV), a common virus that can lie dormant for years.
The Bigger Picture
The existence of post-vaccine complications isn’t new. “Post-vaccination syndrome is real and has been found [to occur] from many vaccines, including COVID,” said Dr Marc Siegel, a clinical professor of medicine at NYU Langone Health.
Dr Siegel pointed to a potential disruption in immune function among those affected. “They may also experience immune disruption, which takes the form of elevations in inflammatory immune cells (CD8 and TN alpha) and a decrease in cells that help resolve inflammation and infection (CD4 helper cells),” he said.
For now, researchers agree that much remains unknown. “We’re only just starting to make headway in understanding PVS,” said Harlan Krumholz, a professor of cardiology at Yale School of Medicine. “Every medical intervention carries some risk, and it’s important to acknowledge that adverse events can occur with vaccines.”
Hope for Future Treatments
The goal, according to scientists, isn’t to dissuade vaccination—it’s to ensure that those who suffer complications get the medical support they need.
“Our responsibility as scientists and clinicians is to listen to their experiences, rigorously investigate the underlying causes, and seek ways to help,” said Krumholz.
Siegel agrees, emphasising that further research is necessary to determine how common prolonged vaccine side effects are and how they can be treated.
While there’s no definitive cure yet, Yale’s findings mark an important step. With continued study, those suffering from PVS may finally get the answers—and treatments—they’ve been waiting for.
