Last week, President-elect Joe Biden said that he will ask everybody in the nation to wear masks for the first 100 days after he takes office.

“Just 100 days to mask, not forever. One hundred days. And I think we’ll see a significant reduction,” Biden told CNN in an interview on December 3.

Additionally, the President-elect said, he will make masks mandatory in federal buildings and on interstate transportation. In recent months, Biden has repeatedly emphasized that masks—along with other measures like social distancing and hand hygiene—are vital for combating COVID-19.

As the novel coronavirus has continued to surge across the country, the U.S. reached a record-high seven-day average of more than 196,200 new cases of COVID-19 over the first week of December. The U.S. also hit a new record for its highest weekly death toll, with a seven-day average of 2,249 deaths last week. If everyone were to follow Biden’s request, though, there would be a substantial drop in new cases, hospitalizations, and deaths from COVID-19, experts say.

“It would be enormously positive; it’s not going to solve all the problems, but certainly…it would have a fairly sizable, perhaps even profound, impact on reducing ongoing transmission,” says Barun Mathema, an infectious disease epidemiologist at the Columbia University Mailman School of Public Health. “It’s a very modest ask given where we are at.”

How quickly the spread of COVID-19 would slow if everybody wears masks once Biden takes office depends on a number of variables, Mathema says. Communities across the U.S. have all adopted their own blend of rules around social distancing, business operations, gathering sizes, and other disease-prevention strategies. “This has made it very difficult to pinpoint and say, ‘Aha, this is what’s going to make all the difference,’” Mathema says.

However, the marked impact of mask-wearing can be seen when comparing counties that have adopted masking mandates to those that haven’t, says Lisa Maragakis, senior director of infection prevention at the Johns Hopkins Health System. This summer, COVID-19 incidence dropped in 24 counties in Kansas that required masks in public spaces. Meanwhile, COVID-19 cases continued to rise in the 81 counties that opted not to require masks.

“When [masks are] worn in combination with physical distancing, we can really make enormous strides to interrupting transmission of the virus,” Maragakis says. The more people mask up, the larger these strides will be. Still, even an incremental boost in the number of people who consistently wear masks would have an impact.

“If we increase the number of individuals wearing masks from where we are today—and particularly in certain parts of the country where there is less mask usage—anything is better than nothing,” Mathema says. One advantage of masks is that they are much less disruptive to people’s lives than other interventions such as school and business closures, he adds. “Nobody is delighted to wear masks; nobody wants to wear masks, but it’s not such an onerous thing to do.”

Even after the first 100 days of the Biden administration are up, you should still hang onto your mask, Mathema says. “Mask-wearing…shouldn’t suddenly go out of fashion,” he says. Once a COVID-19 vaccine is approved, it’s likely to take months for it to become widely available. And, while early data indicate that several vaccine candidates are safe and effective in preventing serious illness, more research is needed to pin down how long that immunity lasts and whether somebody who has been vaccinated can still unwittingly harbor the virus and transmit it to others.

“There are likely some really rough days, rough weeks ahead of us, and so it is exceptionally important to be maintaining social distancing, not just mask-wearing…and unfortunately fighting the urge that we all have at this time of year to visit loved ones [and] friends and celebrate the holidays [with] traveling and mingling and big crowds,” Mathema says.

It’s also important to avoid spending time around people who aren’t wearing masks when possible; not to let your guard down around coworkers, neighbors, friends, and extended family; and to recognize that a negative COVID-19 test can’t guarantee a safe gathering with other people, Maragakis says.

“We are in a critical period right now; we have the vaccine on the horizon that is a light at the end of a very dark tunnel,” she says. “And in the meantime, we have the opportunity to prevent an enormous number of deaths between now and then.” It’s as simple as wearing a mask, washing hands, and social distancing.