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. Persistent spike protein has been associated with long COVID as well. “That was surprising, to find spike protein in circulation at such a late time point,” said Iwasaki. “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. Along with spike protein persistence, the researchers are assessing the contributions of autoimmunity, tissue damage, and Epstein-Barr Virus (EBV) reactivation.