I suppose one couldn’t know for sure either way, but I heard they had several repeat tests that came back negative. Doesn’t necessarily mean it was a false positive though. It could be that they cleared the virus. I don’t know how often they test it’s entirely possible that they hadn’t been tested recently until the veep came to the studio, and were asymptomatic for the last x week(s).
And of course, could be different testing methods and cycle counts. Maybe for veep appearance they run a higher cycle count and/or use a different lab and procedures than the routine tests used by the tv studios.