What should we make of the new CDC guidance for isolation and quarantine?

Note: The Centers for Disease Control and Prevention continued to update its guidance following the publication of this post. The most up-to-date guidance can be found here.) 

On December 27, 2021, the Centers for Disease Control and Prevention changed its guidance for some people who test positive for COVID-19.

Instead of 10 days of isolation from either the time you test positive or the day your symptoms begin, the agency says COVID-positive people can now end isolation after five days if you don’t have symptoms, or if your initial symptoms have improved.

The change, says CDC, comes amidst evidence that people are typically most infectious — and therefore, most likely to transmit the virus to other people — in the days immediately preceding and closely following the start of their illness.

However, a critical element of this guidance is that if you do test positive, you should continue to wear a mask around other people for an additional five days after you leave isolation. This is to further reduce the chances you spread the virus to someone else, says epidemiologist Ajay Sethi, a professor of population health sciences at the University of Wisconsin School of Medicine and Public Health.

A woman with blonde hair, wearing a surgical mask, sits in a red chair typing at a computer.

People without symptoms can now leave isolation after five days of testing positive for COVID-19 but they should continue to wear a mask for an additional five days to further reduce the chances they might spread the virus to others. Photo: Jeff Miller, UW–Madison

Upgrading to well-fitting medical-grade masks or similar — such as surgical masks, KN95s or N95 respirators — is important in light of new, more infectious variants of SARS-CoV-2. And, while masks are not 100 percent effective, “mask use is imperative” under the CDC’s latest isolation guidance, explains Sethi, director of the Master of Public Health program.

As of Dec. 29, the agency had not clarified what it means to have improving symptoms, but people have generally been permitted to leave isolation in the past once they’d stayed home for the minimum amount of time, had been fever-free for 24 hours without fever-reducing medication, and had seen improvements in any other symptoms they may have had.

Importantly, CDC’s updated guidance is not intended to shorten isolation for everyone who tests positive. Anyone who continues to remain ill, without significant symptom improvement, should remain in isolation beyond five days. The agency continues to recommend that people with severe illness or people who are severely immunocompromised isolate for up to 20 days, as warranted.

While it was not in the original guidance, the CDC later added a recommendation that anyone who is able and would like to test do so toward the end of a five-day isolation period, if you meet the criteria for shortened isolation. You should use an antigen test and, if your test is positive, you should continue to isolate until it has been 10 days. Negative results should not be assumed to mean you are no longer infectious, which is why CDC continues to recommend anyone who tests positive wear a mask for a full 10 days.

“Any positive antigen test should be assumed to mean you’re infectious, but a negative test does not always imply non-infectiousness unless it is repeatedly negative,” Sethi says. “I also find it helpful to remember that, by default, the majority of asymptomatic people following exposure don’t ever get tested.”

For most people, consulting with your doctor may be the best way to make sense of what to do following a COVID-19 diagnosis.

What else has changed?

The CDC now also recommends that anyone exposed to COVID-19 — whether vaccinated, unvaccinated, or vaccinated and boosted — get a test five days after exposure, or sooner if you develop symptoms. If you test positive, you should follow the instructions for isolation.

You should also wear a mask for 10 days following your exposure, regardless of your vaccination status.

If you are vaccinated and boosted you do not need to quarantine, but if you are unvaccinated, or eligible for a booster but not yet boosted, you should quarantine for at least five days and wear a well-fitting mask for an additional five days.

A hand holds a vial of COVID-19 vaccine and uses a needle to withdraw the liquid.

Getting vaccinated and boosted when eligible remain the best ways to protect yourself from the worst outcomes of COVID-19. Vaccinated individuals are also not required to quarantine after an exposure, but should wear a mask for 10 days and get tested after 5, or sooner if you develop symptoms. Photo:Jeff Miller, UW–Madison

This means that if you were vaccinated more than six months ago with an mRNA vaccine, or more than two months ago with Johnson & Johnson, you should plan at least a five-day quarantine.

With the omicron variant, booster vaccines are important for strong protection. Vaccinated people remain much less likely to develop severe illness or require hospitalization.

Reacting to the update

As has been the case almost every time the CDC makes major updates to its COVID-19 guidance, scientists, medical professionals, public health experts and many others have registered strong initial reactions. We are nearly two years into the pandemic and fatigued by vigilance, by constantly adapting to change, by calculating ever-evolving risks, by trying to get more Americans vaccinated, and by concern for people and systems we care about.

We might also be anxious and frustrated when decision-makers issue new policies that must often take multiple factors into account. These decisions are usually made with the entire nation or other large populations in mind, but they can feel personal, and may not always align with what we’d personally prefer to happen.

The new guidelines, say Sethi, “come at a time when health care systems and other employers are at risk for not maintaining enough staff to serve society.”

The drastic increase in cases wrought by the omicron variant risks scenarios all over the country in which essential functions can’t be performed, as people isolate or quarantine in large numbers.

“The alternative (to shortened isolation and quarantine) is something that no one wants, and that’s to shut down completely,” Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and chief medical advisor to the president, recently explained in an interview about the CDC’s guidance.

Some people may also worry that others won’t follow the rules — that unvaccinated people won’t quarantine, or that someone will leave isolation too soon. At this point in the pandemic, we know that some people have been making decisions independently of expert guidance. Only two-thirds of the country is fully vaccinated and large swaths of the country rarely wear masks. Shorter isolation, some experts say, might encourage more people to test and follow guidance.

The best guidance has remained fairly straightforward:

Get vaccinated and stay up to date on vaccine recommendations.

When transmission is high, wear a mask and limit your social gatherings, especially indoors.

Get tested if you have symptoms.

Stay home when you’re sick.

Stay away from other people until you’re better.

Editor’s note: An earlier version of this story covered CDC’s initial lack of a recommendation to test toward the end of a five-day isolation period. Several experts preferred a testing recommendation. On  Jan. 4, 2022, the CDC added a recommendation for antigen testing for anyone able and willing. This was updated in the post.