I posted this same situation about my brother a week or so ago.True story....we are getting ready to vacation in Mexico, so we are all gearing up for testing and what not. Get a little side tracked discussing vaccination status of the group and my sister, who is a practicing ER doc in the Cincinatti area, shares that they had a patient this week who had COVID months ago, then both doses of the Phizer vaccine, presented to the ER with symptoms and is positive again!