Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases and voice of expertise about the COVID-19 pandemic in the United States, expressed optimism that stadiums could be full again in 2021, per an interview with Yahoo Sports on Monday. This includes the potential for NBA teams to have their arenas filled to full-capacity crowds during this upcoming season.

Of course, that projection is contingent on whether people are willing to get the vaccine for the respiratory disease when it becomes available. Here's what Fauci had to say about the timeline of what needs to happen in 2021 in order for sports to begin going back to normal:

"We're gonna be vaccinating the highest-priority people [from] the end of December through January, February, March. By the time you get to the general public, the people who'll be going to the basketball games, who don't have any underlying conditions, that's gonna be starting the end of April, May, June. So it probably will be well into the end of the summer before you can really feel comfortable [with full sports stadiums] - if a lot of people get vaccinated. I don't think we're going to be that normal in July. I think it probably would be by the end of the summer."

What he seems a bit more confident about, which makes sense given the timeline he laid out, is NFL stadiums in the 2021 season being open to full capacity.

But, the desire to vaccinate is the biggest determining factor. As things currently stand, skepticism over receiving the vaccine has been decreasing, though there was concern that roughly half of all adults were apprehensive about it in polls as late as September.

There's no agreed upon target for the number of people who need to be vaccinated in order to get stadiums full again, but Fauci estimates it is somewhere between 75 and 85 percent. That means the return to full stadiums will be a gradual task. 

But even as the crowd sizes return to a semblance of normalcy, there are certain things from the peak of COVID-19 pandemic that should remain the same. Wearing masks is one, according to Fauci.

"I think we should be wearing masks as long as there is any of this [virus] around," he said. "Because it's an easy thing to do."