New guidelines from the Centers for Disease Control and Prevention for community masking are a welcome change. They are reasonable, well-timed and consistent with the science that needs to be guiding the United States’ pandemic response. They also mark a turning point for how people, institutions and governments should respond to the coronavirus.
The C.D.C. is shifting away from relying solely on cases of the coronavirus in the community and toward a broader view of risk that includes data on the levels of severe disease as well as hospital capacity. The agency’s new guidance uses a system that categorizes counties as low, medium or high risk for poor outcomes, and the C.D.C. recommends people in high-risk areas wear a mask in public indoor settings. To calculate these categories the C.D.C. is using multiple metrics beyond simply case counts; importantly, health care system capacity. Under the new system, more than 70 percent of the U.S. population is in an area with low or medium community risk right now.
This change may feel like a sharp break from prior guidance, and in some ways, it is. But at this point in the pandemic, the change is also entirely appropriate.
A virus and a population interact in a dizzyingly dynamic system, with mutations and layering immunity forming different profiles of population-wide risk at different times. Policy does and should recognize when these factors have changed enough to justify new approaches.
Omicron is very different from the coronavirus variant that arrived on our shores two years ago. And the population is different too: A large majority of Americans are now vaccinated or recently infected. Effective therapies are becoming more widely available and, precisely because the disease is so virulent, caregivers have battle-won experience in treating it even in the face of stretched hospital capacity.
For nearly two years, basing national Covid-19 guidance on new case counts made sense. Health experts knew that a reliable proportion of those cases would result in hospitalizations, and a proportion of those hospitalizations would lead to deaths. There was a tight link between cases and severe disease for most of the pandemic: as cases spiked, hospitals would reliably fill up and deaths would soon follow. This link among cases, hospitalizations and deaths was the bedrock of guidance to minimize infections through public health measures like mask wearing, crowd avoidance and widespread testing.
But the Omicron surge changed everything. The variant arrived when a larger proportion of the U.S. population had some immunity — either because of vaccination or recent infection. Because Omicron also has a high degree of immune evasiveness, many people getting infected have had Covid before or have been vaccinated and even boosted, which meant that they were far less likely to get severe disease. And finally, compared to its predecessor Delta, the Omicron variant appears to inherently be somewhat less severe, although for unvaccinated or unboosted individuals, it is still quite deadly. Ultimately, Omicron caused a very large surge in cases and left in its wake a very different reality to which the C.D.C. is now responding.
Today, because there is a high degree of population immunity, the ability of the virus to cause severe disease and death is far more variable. Someone vaccinated a month ago is not as vulnerable to severe disease as someone who recovered from an infection 18 months ago. If there are 1,000 infections in Massachusetts today, the number of those that will develop into severe illness depends on whether the individuals are vaccinated, boosted, previously infected or immunologically naïve (that is, neither previously infected nor vaccinated). The mix of those four categories varies dramatically across the nation. That’s why relying entirely on cases to dictate risk no longer makes sense, and shifting to measures of severe disease levels, like hospitalizations, is much more appropriate.
In some places, there are plenty of hospital beds and staff and therefore, hospitalizations don’t cause the same stress as they would in places with far less capacity. Think of a city like Boston with many large hospitals versus rural Ohio where there are far fewer resources per capita. In that context, a surge of hospitalizations in Boston has fewer dire consequences than one in rural Ohio. Hospital capacity matters enormously, not just to care for patients with Covid-19 but to secure all the essential services that hospitals provide under normal circumstances. One of the tragedies of Covid surges is that when hospitals get stretched, they can no longer provide high-quality care for patients with heart attacks, injuries from car accidents, appendicitis, cancer or the myriad other conditions that need to be treated. That’s why paying close attention to health care capacity is a welcome change in a nation with large variations in that capacity.
Increases in cases of Covid-19 are still an important early warning signal, even as the link between cases and hospitalizations and deaths has become far weaker and variable. Cases still precede severe disease. And of course, cases, especially in unvaccinated people, can still cause long-term complications. Therefore, keeping an eye on case numbers and using them as a part of the portfolio of metrics guiding policy remains important, as the C.D.C. is doing.
The C.D.C.’s role at moments like this is advisory. The agency provides guidance on the right thing to do, but it is up to elected officials and local health departments to use that guidance as they see fit. Many leaders, Republicans and Democrats, have already taken versions of the steps the C.D.C. recommended today. For the C.D.C. to remain credible and useful to the policymakers who rely on it, it must be willing to update its guidance when facts change and to take into account where Americans are in their ability to adhere to recommendations. Highlighting the importance of mask wearing in high-risk areas with limited hospital capacity, but not pushing for masking in areas with little severe disease strikes the right balance.
As Americans enter this new phase of the pandemic, mitigation efforts like masking, testing and avoiding gatherings will remain important tools to manage the spread of the disease, especially when there’s threat of another surge. Changing the way we use these tools — when to pull them out and when to put them away — is a critical part of managing a pandemic effectively. The C.D.C.’s new guidance does just that by focusing on the metrics that matter most at this point in the pandemic.
Dr. Ashish K. Jha is dean of the Brown University School of Public Health.
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