Dr. Carlos Del Rio said US Covid cases could decline dramatically into May as long as the US continues to aggressively vaccinate and convince reluctant communities to get vaccinated.

“I worry … that we are quickly moving our country from a supply problem, a vaccine shortage problem, to a demand problem,” said Del Rio. “I’ll tell you that the most reluctant communities are mostly white evangelicals, and we really need to go to these communities to vaccinate them.”

There are roughly 41 million white evangelical adults in the U.S. and roughly 45% said they wouldn’t be vaccinated against Covid-19 in late February, which makes them the least likely population group to do so, according to the Pew Research Center.

Half of all American adults have received at least one dose of a coronavirus vaccine. Of those 65 years old and older, 81% have received one dose or more, and about two-thirds are fully vaccinated, according to the Centers for Disease Control and Prevention.

Del Rio, a professor of medicine who specializes in infectious diseases at Emory University School of Medicine, told CNBC’s “The News with Shepard Smith” that the US may be able to follow Israel’s example and requirements Increasing masking outdoors when transmission in the community drops.

“If we can reduce community transmission to below ten cases per 100,000 population, I don’t think it will be necessary to wear masks outdoors,” said Del Rio.

Host Shepard Smith also asked Del Rio about Texas and those citing the state as an example of successful mask mandate lifting. According to Johns Hopkins University, the average daily Covid cases in Texas have dropped 41% since Governor Greg Abbott lifted the mask mandate 40 days ago. Del Rio noted that there are still many unknowns about Covid and that states should still proceed with caution in lifting Covid restrictions.

“I think sometimes we wonder if a place like Texas is good or happy, and I think it’s luckier than good, frankly,” said Del Rio.

CDC director Dr. Rochelle Walensky has warned that Americans should still be on guard over Covid.