This Irvine company tested most of its workforce for coronavirus antibodies. The results were startling

Kam Kalantar-Zadeh, a specialist in internal medicine, nephrology and pediatrics at UC Irvine [said] “As an analogy, the common cold has no cure, no long-lasting immunity — we can get several colds a year — and no cure, which may be the emerging bitter reality in dealing with COVID-19.” … Philip L. Felgner, director of UC Irvine’s Vaccine Research and Development Center … [said] “We don’t know how much of the 10% is due to cross-reactivity from other common coronaviruses,” he said. “He would need to compare (antibody) levels from specimens collected several years ago before the outbreak.” Felgner’s lab has many thousands of pre-outbreak specimens that could be used for comparison, he said.