The five-day isolation period should also occur if you’re asymptomatic and you test positive. “Once you’ve got a positive test, you’ve got it, you’re in a category where you have virus,” said Bernadette Boden-Albala, the director and founding dean of the University of California, Irvine’s Program in Public Health. If this is the case for you, the five-day period begins the day after you test positive. The actual day you test positive is part of day zero. … “If you get boosted, you are much less likely to get severe disease or even have a breakthrough,” Boden-Albala said.