Cases are "plateauing" instead of surging in coronavirus hot zones in states including California and Texas, likely because residents are wearing face masks and social distancing, Health and Human Services Secretary Alex Azar said on Monday.

"While Dr. [Deborah] Birx says we're seeing signs of plateauing, we're not out of the woods yet," Azar told "Fox & Friends." "We think it's due to the fact that people are actually wearing their masks ... They're social distancing."

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"The governors have closed some of these bars where you just can't keep socially distant, and you're not going to wear a face covering," Azar said.

The next several months will be crucial because the U.S. has "really incredible shots at therapeutics ... as well as vaccines," Azar said.

In this March 16, 2020 file photo, a subject receives a shot in the first-stage safety study clinical trial of a potential vaccine by Moderna for COVID-19, the disease caused by the new coronavirus, at the Kaiser Permanente Washington Health Research Institute in Seattle. (AP Photo/Ted S. Warren, File)

On Monday afternoon, the secretary and President Trump will visit Fujifilm Diosynth Biotechnologies, which manufacturers components of a potential coronavirus vaccine, in Morrisville, N.C.

"The president and I are going down to Research Triangle in North Carolina today, where he's going to get to see one of the five vaccines we have invested in," Azar said.

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Also on Monday, Massachusetts biotech company Moderna announced it started its Phase 3 trial of a coronavirus vaccine. Moderna is working with NIH on the vaccine, and the effort is part of the Trump administration's Operation Warp Speed.