CDC rolls out new formula for mapping Covid-19 risk 

Hospitalizations and capacity now main factors, CDC focuses on preventing worst outcomes

By Polly Mikula

The Center for Disease Control and Prevention’s (CDC) rolled out new guidance qualifying nearly 70% of the nation to unmask, on Feb. 25. Prior to the changes, only about a third of the counties were assessed as low or medium risk.

Specifically, under the new formulas, 23% of U.S. counties were deemed “low” risk, 39.6% “medium,” and 37.3%  “high” — each risk level has correlating guidance, but only “high” includes universal masking indoors.

The announcement is largely seen as the impetus for many states (including Vermont) to relax their own masking guidelines, if they hadn’t done so already. 

The new CDC guidance is based on risk of severe outcomes taking into account hospitalization rates and hospital capacity as well as known cases (with the case threshold for “high” risk increasing to over 200 cases per 100,000 up from 100 case per 100,000.) Previously the CDC’s risk formula had been based primarily on (the lower) case threshold and case positivity rates.

CDC Director Dr. Rochelle Walensky and Dr. Greta Massetti from the Covid-19 Incident Management Team made the announcement at a press conference, Feb. 25. 

“Today, CDC is updating its framework to monitor the level of Covid-19 and communities,” Walensky began. “We’re in a stronger place today as a nation with more tools to protect ourselves in our communities from Covid-19; like vaccination, boosters, broader access to testing, availability of high quality masks, accessibility to new treatments, and improved ventilation. Over 200 million people have received a primary vaccine series and nearly 100 million have been boosted, and millions more have had prior disease. With widespread population immunity, the overall risk of severe disease is now, generally, lower.

“Now, as the virus continues to circulate in our communities, we must focus our metrics beyond just cases in the community and direct our efforts toward protecting people at high risk for severe illness and preventing Covid-19 from overwhelming our hospitals and our healthcare systems.

“This new framework moves beyond just looking at cases and test positivity to evaluate factors that reflect the severity of disease, including hospitalizations and hospital capacity, and helps to determine whether the level of Covid-19 and severe disease are low, medium, or high in a community,” she said. “This updated approach focuses on directing our prevention efforts towards protecting people at high risk for severe illness and preventing hospitals and healthcare systems from being overwhelmed.”

Hospitalization metrics are reported daily to the CDC by healthcare facilities across the U.S.

“There are 6,000 hospitals in the United States that are required to report those data every day — Monday through Friday — and usually there’s better than 95% coverage on any given day,” said Dr. Massetti. “So hospitals are very consistently compliant with reporting those data… The case data are also largely reported from public health laboratories.”

“Please remember that there are people who remain at higher risk for Covid-19 and who may need additional protection. Those who are immunocompromised or have underlying health conditions, those who have disabilities, or those who live with people who are at risk. Those people might choose to take extra precautions regardless of what level their community is in,” Walensky concluded in her opening remarks.

The CDC also emphasized that, despite the update, there are situations where people should always wear a mask, regardless of level. Those include: if a person has symptoms, if they test positive for Covid-19, or if they have been exposed to someone with Covid-19.

Dr. Massetti then explained the framework and the science behind the new risk level assessments. 

“A community’s Covid-19 level is determined by a combination of three pieces of information: new hospitalizations for Covid-19, current hospital beds occupied by Covid-19 patients or hospital capacity, and new Covid-19 cases. These metrics will tell us if the level is low, medium, or high,” she explained.

The CDC counts anybody in a hospital bed with Covid, regardless of the reason for admission. This is because many jurisdictions can’t differentiate and because regardless of whether or not a patient was admitted with Covid or for Covid, they increase the hospital capacity and they’re resource intensive, Walensky explained. 

“They require an isolation bed. They require PPE. They probably require a higher staff ratio…and they do take a Covid bed potentially from someone else,” she said.

U.S. Covid-19 community levels by county

“Low”

In communities where the level is “low,” there is limited impact on the healthcare system and low amounts of severe disease in the community. The only CDC recommendation is: People should stay up to date with their vaccines and get tested if they’re sick. 

“Medium”

In communities where the level is “medium,” more people are experiencing severe disease in the community and they’re starting to see more impact on the health healthcare system. The CDC recommendation is: People who are high risk, such as someone who is immunocompromised, should talk to their healthcare provider about taking additional precautions and may choose to wear a mask. 

“High”

In communities where the risk is deemed “high,” there is high amount of people experiencing severe disease and high potential for healthcare systems strain. The CDC recommendation is: Everyone wear a mask indoors, in public, including in schools.

Since July, 2021, the CDC had recommended universal masking in schools, no matter what level of impact Covid-19 was having on the community.

“We’ve been reviewing the data on Covid illness in children for two years of a pandemic,” Massetti explained to the press. “And we have seen that although children can get infected and can get sick with Covid, they’re more likely to have asymptomatic or mild infections. So, fortunately, we know that when schools implement layered prevention strategies, that they can prevent SARS COV-2 transmission or transmission of the virus that causes Covid-19 in schools. And we know that also because children are relatively at lower risk from severe illness that schools can be safe places for children. And so for that reason, we’re recommending that schools use the same guidance that we are recommending in general community settings.”

The CDC hopes that the newly assessed risk levels along with additional metrics available locally will help communities across America be more responsive to changing circumstances.

“Communities can use these metrics, along with their own local metrics, such as wastewater surveillance, emergency department visits, and workforce capacity, to update and further inform their local policies and ensure equity and prevention efforts,” Massetti said. “And the categories can help individuals assess what impacts Covid-19 is having so that they can decide if they need to take extra precautions, including masking based on their location, their health status, and their risk tolerance.”

When asked how vaccination rates play into the new CDC equation, Walensky responded: “If someone is unvaccinated and has underlying health conditions, they certainly are at high risk of severe disease. And so it is part of the equation. It’s not among the things that are listed, but certainly it is reflected in who will come into the hospital with severe disease… our most recent data have demonstrated that if you are boosted you’re 97 times less likely to die of Covid than if you’re unvaccinated.”

The CDC announcement came at a time when many governors across the U.S. had, or were planning to, remove universal masking guidance regardless of the CDC assessed risk. When asked by the press if this influenced the change in metrics or the timing of the CDC announcement, Dr. Walensky said it didn’t, adding that the CDC had long been planning to move in this direction.

“What we do know about the current moment is that we’ve seen a decreased severity associated with Omicron. We had many, many more cases than we had hospitalizations, compared with what we saw with Alpha or Delta. And in that backdrop, we also had much more population immunity by vaccination, boosting and prior infection, so many, many of our infections did not result in severe disease; it did not result in increased hospital capacity. And it was in that context that we made this pivot,” Walensky explained.

She added: “We wanted to give people a break from things like mask wearing when our levels are low and then have the ability to reach for them again, should things get worse in the future.  We at CDC will continue to follow the science and epidemiology to make public health recommendations and guidance based on the data. Our new framework was rigorously evaluated both with current data and retrospectively during the alpha, delta and omicron waves and these new metrics have demonstrated predictive capacity for weeks into the future… If, or when, new variants emerge or the virus surges, we have more ways to control the virus and protect ourselves and our communities than ever before.”

In summary Walensky stated: “We wanted to make sure that we were focusing on severe disease because we do want to prevent severe disease. We want to prevent hospitalizations. We want to prevent our hospitals from becoming overwhelmed… We know that there’s going to be transmission of Covid-19 out there. And what we want to do is make sure that our hospitals are okay … the volume of severe disease in the hospital is likely representative of the volume of disease in general in the community. So they are very much linked.”

To find what level any U.S. county is assessed at and the correlating prevention strategies recommended (including where or when to mask) visit: cdc.gov or call 1-800-CDC-INFO. Maps, charts, and data provided by CDC, are updated every Thursday by 8 p.m., according the cdc.gov.