It might not be until fall 2021 that Americans can be completely safe" from COVID-19, Bill Gates said in a Tuesday interview with Judy Woodruff on PBS Newshour. That's because it will take more than a year before a vaccine can be developed and deployed, according to researchers working to develop a treatment for COVID-19. "The vaccine is critical, because, until you have that, things aren't really going to be normal," the billionaire philanthropist told Woodruff. "They can open up to some degree, but the risk of a rebound will be there until we have very broad vaccination." Social distancing is helping to lower the number of COVID-19 cases. The goal, Gates explained, is to get that number down to a point where "contact tracing" (a process in which those within close contact with an infected person are closely monitored) can be done, in order to maintain necessary quarantines. To understand what life in the U.S. will look like six to 12 months from now, Gates suggested China as a good model. "They are sending people back to work, but they're wearing masks. They're checking temperatures. They're not doing large sporting events. And so they have been able to avoid a large rebound," he said. Beyond that, "returning to some semblance of normal," as Woodruff put it, can be predicted by watching the behaviors of other countries. Sweden, for example, isn't "locking down quite as much," so their experience will be informative, Gates explained.