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The director of the Centers for Disease Control and Prevention is once again stressing the importance of masks in the coronavirus pandemic, calling them "more guaranteed" to protect against COVID-19 than a vaccine.

CDC Director Robert Redfield testified before Congress on Wednesday and emphasized to lawmakers that face masks are the "most important, powerful public health tool we have," urging "all Americans" to "embrace" them because doing so could bring the COVID-19 pandemic "under control."

"I might even go so far as to say that this face mask is more guaranteed to protect me against COVID than when I take a COVID vaccine," Redfield said. "Because the immunogenicity may be 70 percent, and if I don't get an immune response, the vaccine is not going to protect me. This face mask will."

These comments from Redfield come after President Trump, who for months resisted wearing a face mask in public, claimed during an ABC town hall on Tuesday that despite what public health experts have said, "a lot of people," such as "waiters," think masks are "not good." Redfield told Congress on Wednesday, "We have clear scientific evidence: [masks] work, and they are our best defense."

During the hearing, after Trump earlier this week claimed a COVID-19 vaccine could be ready in just three or four weeks, Redfield predicted that one could be "initially" available in "very limited supply" in November or December. But in terms of when a vaccine could be "generally available to the American public," Redfield said this could come in "late second quarter, third quarter 2021." Brendan Morrow