The CDC's Ever-Shifting COVID-19 Advice Shows the Agency Is Ill-Suited To Decide Which Risks Are Acceptable

The CDC's recommendations have never been purely a matter of science.


The Centers for Disease Control and Prevention (CDC), which initially said there was no need for most Americans to wear face masks as a safeguard against COVID-19, reversed that position a little more than a year ago. Beginning in April 2020, the CDC said face masks were an essential disease control tool, even for people who have been vaccinated. Yesterday the CDC modified its advice again, saying fully vaccinated Americans generally do not need to wear masks outdoors or indoors, except when required to do so by businesses or the government.

At each turn, the CDC has said its recommendations were informed by the latest scientific evidence. While there is some truth to that claim, it is clear that other, nonscientific factors have played a role in the CDC's shifting attitude toward face coverings as a response to the COVID-19 pandemic. The history of that evolution provides ample reason to be skeptical of both the CDC's specific recommendations and the expectation that all Americans should conform to its notion of safety.

'You Do Not Need to Wear a Facemask'

As late as April 3, 2020—more than two months after the first confirmed COVID-19 case in the United States, when the country was recording more than 26,000 new infections and nearly 1,000 deaths a day—the CDC was telling Americans to "wear a facemask if you are sick." But "if you are NOT sick," it said, "you do not need to wear a facemask unless you are caring for someone who is sick (and they are not able to wear a facemask)." It added that "facemasks may be in short supply and they should be saved for caregivers."

The CDC changed its advice the next day, saying "everyone should wear a cloth face cover when they have to go out in public," because "you could spread COVID-19 to others even if you do not feel sick." It said "the cloth face cover is meant to protect other people in case you are infected." But it added that people should "NOT use a facemask meant for a healthcare worker," meaning surgical masks and N95 respirators. The most effective face coverings, in other words, were still reserved for medical professionals.

"Here's what's changed," then-Surgeon General Jerome Adams claimed on Meet the Press. "We now know that about 25 percent, in some studies even more, of COVID-19 is transmitted when you are asymptomatic or presymptomatic." That estimate actually referred to the percentage of people infected by the COVID-19 virus who never develop symptoms. Then–CDC Director Robert Redfield began citing that number (which was somewhat lower than the CDC's current "best estimate" of 30 percent) on March 31, 2020. But it had been clear at least since February that people could carry the virus for days before they developed symptoms and that some carriers never felt ill.

study published in February 2020, based on 88 cases in Wuhan, China, estimated that the mean incubation period for COVID-19 was 6.4 days. Another study published the same month, based on "publicly available event-date data from the ongoing epidemic," put the incubation period at two to 14 days with a mean of about five days. Based on those findings, the researchers recommended that "the length of quarantine should be at least 14 days." A March 10 study, based on 181 cases, essentially confirmed those results, estimating a mean incubation period of five days and finding that "97.5% of those who develop symptoms will do so within 11.5 days."

January 30 letter to The New England Journal of Medicine, based on several cases in Germany, warned that "asymptomatic persons are potential sources of [COVID-19] infection." A February 13 letter to the International Journal of Infectious Diseases estimated that 31 percent of people infected by the COVID-19 virus did not have symptoms. A research letter published in The Journal of the American Medical Association on February 21 described an asymptomatic carrier from Wuhan who seemed to have infected four other people. A February 26 Global Biosecurity report noted that "asymptomatic transmission has been documented" and "the viral load in symptomatic and asymptomatic people is not significantly different."

report from the World Health Organization published around the same time nevertheless depicted asymptomatic infection as rare. While "asymptomatic infection has been reported," it said, "the majority of the relatively rare cases who are asymptomatic on the date of identification/report went on to develop disease."

When it came to wearing face masks in public to protect others from infection, however, it did not really matter whether carriers were asymptomatic or presymptomatic. The point was that people could transmit the virus without realizing they were carriers. Given the incubation period, that phenomenon had to be common.

'the most important, powerful public health tool we have'

It seems clear that the CDC conflated two issues: 1) whether wearing face masks in public places was a sensible safeguard, and 2) whether there were enough commercially produced masks to supply the general public as well as medical workers.

"Seriously people—STOP BUYING MASKS!" Adams had tweeted on February 29. "They are NOT effective in preventing [the] general public from catching #Coronavirus, but if healthcare providers can't get them to care for sick patients, it puts them and our communities at risk!" In other words, Adams wanted the public to believe the same masks on which health care workers relied somehow stopped working when worn by ordinary Americans.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, likewise questioned the effectiveness of general mask wearing while simultaneously saying that masks should be reserved for health care workers. "There's no reason to be walking around with a mask," he said during a March 8, 2020, interview with 60 Minutes. "When you're in the middle of an outbreak, wearing a mask might make people feel a little bit better, and it might even block a droplet. But it's not providing the perfect protection that people think that it is. And often, there are unintended consequences. People keep fiddling with the mask, and they keep touching their face…When you think 'masks,' you should think of health care providers needing them."

Fauci, like the CDC, was soon singing a different tune. "There should be universal wearing of masks," he told ABC News in August. "If you look at the scientific data, the masks clearly work," he told CNN the following month.

Around the same time, Redfield claimed that face masks provided better protection than vaccination would. "These face masks are the most important, powerful public health tool we have," he told a Senate subcommittee while holding a cloth mask. "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 really should not have gone that far. Although it was not yet clear how remarkably effective COVID-19 vaccines would prove to be, his logic was plainly fallacious even then. He imagined that a vaccine might provoke an immune response in 70 percent of the people who received it. "If I don't get an immune response, the vaccine is not going to protect me," he said. "This face mask will." But face masks, like vaccines, are not 100 percent effective, and there was no reason to think they would provide better protection than vaccination.


Even after clinical trials and follow-up research showed that vaccines not only prevented serious disease and death but also nearly eliminated the risk of asymptomatic infection, the CDC took a suspenders-and-a-belt approach. In early March 2021, the CDC allowed that "fully vaccinated people" could "visit with other fully vaccinated people indoors without wearing masks or physical distancing." They could even "visit with unvaccinated people from a single household who are at low risk for severe COVID-19 disease indoors without wearing masks or physical distancing." But the CDC said they should still "avoid medium- and large-sized in-person gatherings"; "take precautions in public like wearing a well-fitted mask and physical distancing"; "wear masks, maintain physical distance, and practice other prevention measures when visiting with unvaccinated people from multiple households"; and do likewise "when visiting with unvaccinated people who are at increased risk for severe COVID-19 disease or who have an unvaccinated household member who is at increased risk for severe COVID-19 disease."

The CDC loosened up a bit in late April, saying fully vaccinated people "can gather or conduct activities outdoors without wearing a mask except in certain crowded settings and venues." It also said, "You can gather indoors with fully vaccinated people without wearing a mask or staying 6 feet apart."

But the CDC still was recommending masks for vaccinated people in many situations, including "indoor public settings," private gatherings "with unvaccinated people (including children) from more than one other household," and visits with "an unvaccinated person who is at increased risk of severe illness or death from COVID-19 or who lives with a person at increased risk." It also advised vaccinated people to "avoid large indoor gatherings."

As of yesterday, however, the CDC is saying "fully vaccinated people can resume activities without wearing a mask or physically distancing, except where required by federal, state, local, tribal, or territorial laws, rules, and regulations, including local business and workplace guidance." What changed in the last two and a half weeks?

"It was not entirely clear what prompted the new guidance on Thursday," The New York Times notes. "It feels like a huge shift, and I'm not going to follow it," John Swartzberg, an infectious disease specialist at the University of California, Berkeley, told the Times. "Each individual should look at what the CDC is recommending and see if that fits for them." Swartzberg said "this shows tremendous confidence in how well the vaccines work" but added, "The CDC does have data to support this decision. It's not like they're operating on the fly."

Did the CDC acquire those data since April 27, the last time it updated its advice? During a press briefing yesterday, CDC Director Rochelle Walensky cited data from Israel that were available months ago. She also mentioned a study published in the CDC's Morbidity and Mortality Weekly Report on April 2 and another in the same journal that was originally published on April 28. The CDC surely was aware of the results reported in the latter study earlier than that.

Walensky added that other studies have shown that the Pfizer, Moderna, and Johnson & Johnson vaccines are effective against "variants like B1351." Those include two studies of the Pfizer vaccine "published just last week"—one in The Lancet, the other in The New England Journal of Medicine. "Previous research suggested that B.1.1.7 is more infectious and more deadly than other variants, but that vaccines still worked well against it," The New York Times noted. "But vaccines appeared to be less effective against B.1.351, according to earlier studies."

'Why do we have to wear masks?'

Maybe those two studies provided the crucial pieces of evidence that made the CDC comfortable with relaxing its recommendations for vaccinated people. But it is likely that other factors also played a role.

The CDC seems to have recognized that expecting people to continue living constrained lives even after they get their shots reduces the incentive to get vaccinated, especially among Americans who are at low risk from COVID-19. More generally, the CDC's excessive conservatism makes Americans less likely to take any of its advice seriously. As Sen. Susan Collins (R–Maine) noted during Walensky's Senate testimony this week, "It undermines public confidence in your recommendations, in the recommendations that do make sense, in the recommendations that Americans should be following."

Walensky recently has received a lot of criticism for grossly exaggerating the risk of outdoor COVID-19 transmission and for taking an absurdly cautious approach to the relaxation of COVID-19 control measures, epitomized by the CDC's ridiculous, unworkable guidelines for summer camps, which epidemiologists and infectious disease experts criticized as "cruel," "irrational," and "unfairly draconian." An exchange during a CNBC interview on Wednesday highlighted the growing impatience with the CDC's unreasonable conservatism.

"Everybody in my work group is wearing a mask," Shepard Smith told Walensky. "Everyone. Why do we have to? We're all vaccinated. Why do we have to wear masks?"

Walensky could have responded by noting that the most recent CDC guidance actually allowed Smith and his colleagues to take off their masks, as long as no unvaccinated people were around. Instead she said this:

We have to look at the science with regard to how the vaccine has worked in the real-world setting….We were looking for signs to ensure that the vaccine works just as well in the real world setting as it did in the trials. We need to ensure that the vaccines are working against all of the circulating variants that we have here in the United States. We're following that carefully. And then we need to make sure that you're not an asymptomatic carrier, if in fact you're vaccinated. So all of that science is emerging, that's what we're following and we will use to update our guidance.

Walensky added that "we are looking forward to updating our guidance very soon"—the very next day, in fact. It would be unfair to conclude that emerging science played no role in that decision, at least with respect to the effectiveness of the Pfizer vaccine against COVID-19 variants. But it likewise would be a mistake to pretend that the CDC's recommendations are purely a matter of science.

As Swartzberg suggested when he said "each individual should look at what the CDC is recommending and see if that fits for them," deciding what COVID-19 safeguards make sense requires value judgments. People have to weigh whether the tiny, possibly nonexistent risks that worry the CDC are worth the cost of forgoing enjoyable activities and the burden of masking and physical distancing. Public health bureaucrats do not have the information necessary to make that assessment, which depends on individual circumstances and preferences.

Most Americans are not as cautious as Swartzberg—or the epidemiologists recently surveyed by the Times, 80 percent of whom thought everyone should continue wearing masks in public for another year. The more the CDC insists that everyone should adopt its view of acceptable risk, the more Americans will rightly ignore its advice.