Each vial contains five to six vaccine doses. Once a vial is opened, its shelf life is about six hours. “It’s truly a use-it-or-lose-it situation. You can’t just keep it for tomorrow morning’s shift,” said Andrew Noymer, UC Irvine associate professor of public health. … “It really raises the question of whether everyone on duty at the time already got theirs,” including the pharmacist, the person who greets people once they enter the building or custodial staff, he said.