When Will Positive COVID-19 Trends Be Reflected in the CDC's Advice?

Because the agency ties mask recommendations to virus transmission rather than serious cases, its guidance is unlikely to change anytime soon.

Newly identified COVID-19 cases in the United States, which rose dramatically this summer, have fallen sharply since early September. Hospital admissions involving people who tested positive for COVID-19 likewise have dropped precipitously. As of yesterday, the seven-day average of daily deaths, a lagging indicator, was down by 22 percent since September 23, per Worldometer's numbers.

You can start to see why many observers think the worst of the pandemic is behind us. The worst so far, measured by the seven-day average of daily deaths, happened in mid-January, when that number exceeded the previous record set in April 2020.

Even at the peak of the most recent COVID-19 surge, daily deaths were substantially lower than the numbers seen last winter or in the spring of 2020. While the seven-day average of daily new cases rose 14-fold this summer, daily deaths rose eightfold. Last fall and winter, by comparison, daily new cases rose sevenfold, while daily deaths rose fivefold. And in the spring of 2020, deaths rose faster than reported cases, although coronavirus testing was woefully inadequate at that point, meaning that a larger share of infections would have been missed.

The widening gap between case and death trends is what you would expect in a country where a large and growing share of the population is protected against the worst consequences of COVID-19 by vaccination, naturally acquired immunity, or both. Two-thirds of Americans 12 or older are fully vaccinated, while 77 percent have received at least one dose. Americans 65 or older, who face a much higher risk of dying from COVID-19 than younger cohorts, are especially likely to be vaccinated: The rates for that age group are 85 percent and 96 percent, respectively. So it is not surprising that the case fatality rate (CFR)—deaths as a share of reported cases—resumed its downward trend after rising slightly in the first few months of the year.

CFR calculations should be viewed with caution, since the denominator depends on testing practices. But the nationwide CFR was 1.62 percent as of yesterday, more than two-fifths lower than the CFR in October 2020, less than half the CFR at the beginning of August 2020, and roughly a quarter of the CFR in mid-May 2020. Even allowing for the expansion of testing in 2020, these numbers suggest that COVID-19 is less deadly than it was 18 months ago, a year ago, or even a few months ago.

Two potential explanations for the CFR drop are expanded testing, which made it possible to detect a larger share of mild cases, and a younger, healthier mix of patients. A preprint study published in December addresses those possibilities by looking at age-stratified outcomes and focusing on hospitalizations, which "should be less influenced by testing capacity than confirmed cases."

Although "testing increased between the first and second waves," the authors say, that "does not explain away these waves." They report that "age-stratified hospitalization fatality rates improved substantially between the first and second wave in the national data (improving by at least 27%), but did not improve between the first and second wave in Florida (worsening by at least 2.9%)." By December 1, however, "both Florida and national data suggest significant decreases in HFR since April 1st—at least 17% in Florida and at least 55% nationally in every age group."

As the researchers note, those findings are consistent with the hypothesis that improvements in COVID-19 treatment help account for the falling CFR. Widespread vaccination, which did not happen until after the period covered by that study, should now be helping to drive the CFR down further. "For all adults aged 18 years and older," the Centers for Disease Control and Prevention (CDC) reported based on data through August 2021, "the cumulative COVID-19-associated hospitalization rate was about 12 times higher in unvaccinated persons." It estimates that unvaccinated patients are 11 times more likely to die from COVID-19 than fully vaccinated patients.

So far these positive trends have had no discernible impact on federal COVID-19 advice or on the policies of jurisdictions inclined to follow it. Vaccination is authorized for all Americans 12 or older and will soon be extended to younger children. Minors face a tiny risk of dying from COVID-19 in any case. Yet the CDC still says everyone, from toddlers to vaccinated adults, should "wear a mask indoors in public." Officially, that advice applies to vaccinated people only if they live in "an area of substantial or high transmission," but that description still covers nearly the entire country.

The CDC is likewise sticking with its recommendation that everyone in schools, regardless of age or vaccination status, wear a mask throughout the day, despite the lack of evidence that the benefits of that precaution outweigh the substantial burdens it imposes. Yesterday Florida's new surgeon general, Joseph Ladapo, who opposes school mask mandates, called the evidence in their favor "very weak," saying "there is a substantial gap between the quality of the data" and "what we're hearing from some of our public health leadership."

That's a fair assessment. At the point when the CDC issued its current recommendations for schools, it was not able to cite any research showing a statistically significant relationship between mask mandates and reduced virus transmission among students. Nearly all of the studies on which it relied did not even compare schools with mandates to otherwise similar schools without them.

A CDC study published last month (i.e., after the agency was already recommending masks for all students) found that Arizona schools where masking was optional were more likely to see COVID-19 outbreaks. But the researchers did not control for vaccination rates or other precautions that schools with mask mandates may have been more likely to implement, both of which could have affected the odds of an outbreak.

A recent Twitter exchange gives you a sense of how desperate the Biden administration is to support its predetermined conclusion that students should be forced to wear masks—a safeguard the Education Department views as so important that it may be mandatory under federal laws protecting students with disabilities from discrimination. "Let's be data-driven and follow the science when it comes to protecting our students in schools," Secretary of Education Miguel Cardona tweeted on September 27. "What does science say about the importance of masking in school?"

Cardona mentioned "a Wisconsin study," which he said found "schools that required masking had a 37% lower incidence of COVID-19 than the surrounding community." That gloss provoked a response from the senior author of that study, epidemiologist Tracy Beth Hoeg. "Our study is not able to give any information about the role masks played in the observed low in-school transmission rates," she wrote. "We had no control group so don't know if the rate would have been different without masks."

Hoeg's study, which was published in the January 29 issue of the CDC's Morbidity and Mortality Weekly Report, found that "reported student mask-wearing was high" and "transmission risk within schools appeared low." But as Hoeg noted, it is impossible to say to what extent the former explains the latter, because the researchers did not compare schools with different policies. The same is true of a Utah study that Cardona also cited. If Cardona, who claims to "follow the science," had solid evidence that mask mandates are as vital as he claims, he would not be citing studies like these to prove a hypothesis they did not even test.

Assuming that school mask mandates have a significant impact on virus transmission, that does not necessarily mean the benefit is worth the cost, especially given the wide availability of vaccines and the extremely low infection fatality rate among children and teenagers (on the order of 0.002 percent, according to a CDC estimate). Yet the CDC acts as if the cost-effectiveness of school mask mandates is beyond serious dispute, even as it searches for evidence to support that conviction.

Let's say the CDC is right in thinking that mask mandates in schools are a sensible precaution under certain conditions. What happens when conditions change? At what point will the CDC decide that mask mandates don't make sense anymore?

As Reason's Matt Welch notes, CDC Director Rochelle Walensky seems to imagine that "universal masking" will continue even as mass vaccination of younger students proceeds. That is consistent with the CDC's general recommendation that people should continue wearing masks even after they've been vaccinated. But indefinite mask mandates will eventually prove untenable, even in places where parents and school officials are inclined to trust the CDC.

By tying its mask recommendations to the level of community transmission, the CDC guarantees that its advice won't change in any place where its criteria for "substantial" spread are satisfied, meaning that the number of new cases per 100,000 people in the last seven days is 50 or more and the test positivity rate is 8 percent or more. Currently 94 percent of U.S. counties exceed that threshold. But focusing on new cases is misleading when people infected by the coronavirus are less and less likely to die as a result. The merits of COVID-19 safeguards, including masks and vaccination, ultimately depend on how effective they are at preventing life-threatening cases rather than infections in general.