CDC director Robert Redfield said face masks may be more effective than a vaccine in preventing individual coronavirus infections

• CDC director Robert Redfield said on Wednesday that wearing a mask might be "more guaranteed" to protect an individual from the coronavirus than a vaccine.
• Redfield's comments came in response to a Senator's question about whether President Trump is undercutting coronavirus-prevention efforts by forgoing a mask in public settings.
• Hours later, Trump said Redfield made a "mistake."
• But studies have shown that mask-wearing effectively prevents transmission of the coronavirus.
• The CDC recommends their use in public and when social distancing is difficult.

Centers for Disease Control and Prevention director Robert Redfield told a Senate subcommittee on Wednesday that wearing a face mask could be more effective in preventing an individual coronavirus infection than getting a vaccine.

Redfield's comments came as a response to Senator Jack Reed, who asked whether President Donald Trump's decision to forgo a face mask in most public settings undercuts "one of the most important steps an American can take to defend themselves and the country."

"I'm not gonna comment directly about the president, but I am going to comment as the CDC director that face masks, these face masks, are the most important powerful public health tool we have," Redfield replied.

"They are our best defense," he added. "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, because the immunogenicity may be 70%. And if I don't get an immune response, the vaccine is not going to protect me. This face mask will."

Hours later, at a Wednesday evening press conference, President Trump refuted Redfield's statements.

"The mask is not as important as the vaccine," Trump said. "The mask, perhaps, helps."

He added: "When I called up Robert today, I said, 'What's with the mask?' He said, 'I think I answered that question incorrectly."

Trump suggested that "as far as the mask is concerned, he made a mistake."

We'll still need masks after a vaccine is authorized

Immunogenicity is the term for a vaccine's ability to provoke an immune response against a virus. An ideal vaccine gives what's called sterilizing immunity, which means it reliably protects anyone who gets it from being infected by a given pathogen.

In the case of the coronavirus, however, developers aren't aiming for sterilizing immunity, at least not at first. They're mainly aiming to reduce disease.

For instance, Moderna's stage 3 vaccine trial – the candidate's final large human trial before it could receive emergency authorization – aims to show the set of shots is at least 60% effective at preventing COVID-19.

However, the FDA has said it will grant authorization to a vaccine even less effective than that: The candidate just has to be at least 50% more effective than a placebo at preventing or reducing the severity of the disease.

For this reason, the early vaccines won't make life go back to normal after they're authorized — and they won't even render masks unnecessary, as Maria Elena Bottazzi, a vaccine developer at Baylor College of Medicine, previously told Business Insider.

"The moment you get a vaccine doesn't mean you're going to put your mask in the trash," Bottazzi said. "That is not going to happen. I hope people don't think that is going to be the magic solution for all."

Masks are effective in preventing the coronavirus' spread

Face masks aren't immunogenic (they don't stimulate the body's immune system), so it's not possible to directly compare the effects of a vaccine to those of face masks. However, study after study has shown that masks are effective in reducing the spread of the coronavirus.

A June study published in the journal Health Affairs, for example, showed that across 15 US states and Washington, DC, mask mandates led to a significant slowdown in COVID-19 case growth rates. Three weeks after the mandates, case growth had slowed by two percentage points.

Additionally, a preliminary analysis of 194 countries suggested that countries with cultures or guidelines supporting mask-wearing saw only a 7% increase in coronavirus deaths per capita after their first case was reported, compared with a 55% increase in deaths in countries without mask recommendations or mask-friendly cultures.

In one particularly compelling case study, two hair stylists in Missouri had close contact with 140 clients while they were both sick with COVID-19 but did not yet realize it. The stylists and all of their clients wore face masks, and none of the clients that researchers later tracked down tested positive.

The CDC recommends everyone wear masks in public and when around people who aren't part of your immediate household.

Redfield has become a vocal supporter of widespread mask-wearing: In a July editorial published in the Journal of the American Medical Association, Redfield called for all US residents to wear masks, saying "there is ample evidence" that asymptomatic people can spread the disease.

"If we can get everybody to wear a mask right now, I really do think in the next four, six, eight weeks ... we can get this epidemic under control," Redfield said during an interview that same week with Dr. Howard Bauchner, JAMA's editor-in-chief.

This story has been updated to include Trump's statements in response to Redfield's.