COVID-19 Resource Center

COVID-19 Resource Center


CDC Updates and shortens recommended isolation and quarantine period for general population. Accessed Dec. 28, 2021.

Disclosures: Adalja and Walensky report no relevant financial disclosures.
December 28, 2021
2 min read

CDC halves recommended isolation time to 5 days if asymptomatic


CDC Updates and shortens recommended isolation and quarantine period for general population. Accessed Dec. 28, 2021.

Disclosures: Adalja and Walensky report no relevant financial disclosures.
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In updated guidance, the CDC said that asymptomatic people with COVID-19 can isolate for 5 days instead of 10, followed by 5 days of wearing a mask around other people.

Halving the recommended isolation period was “motivated by science demonstrating that the majority of SARS-CoV-2 transmission occurs early in the course of illness, generally in the 1-2 days prior to onset of symptoms and the 2-3 days after,” the CDC said.

Crowd with masks
The CDC said people with COVID-19 can leave isolation after 5 days if they are asymptomatic but should continue to wear a mask for 5 days around other people. Source: Adobe Stock

“Therefore, people who test positive should isolate for 5 days and, if asymptomatic at that time, they may leave isolation if they can continue to mask for 5 days to minimize the risk of infecting others,” it said.

The CDC also updated quarantine guidance for people exposed to COVID-19. The guidance for people who are unvaccinated and people who are more than 6 months removed from a two-dose messenger RNA series (Moderna, Pfizer) or 2 months removed from a shot of the Johnson & Johnson vaccine is the same: quarantine for 5 days followed by strict mask wearing around others for another 5 days.

“Alternatively, if a 5-day quarantine is not feasible, it is imperative that an exposed person wear a well-fitting mask at all times when around others for 10 days after exposure,” the CDC said.

People who have received their booster shot, on the other hand, do not need to quarantine but should wear a mask around others for 10 days after the exposure, according to the new guidance.

“For all those exposed, best practice would also include a test for SARS-CoV-2 at day 5 after exposure. If symptoms occur, individuals should immediately quarantine until a negative test confirms symptoms are not attributable to COVID-19,” the CDC said.

The updates came amid a surge in cases caused by the highly transmissible omicron variant. The CDC noted evidence from South Africa and the United Kingdom that mRNA vaccine effectiveness against omicron is approximately 35% following two doses, but a booster dose raises effectiveness to 75%.

“The omicron variant is spreading quickly and has the potential to impact all facets of our society. CDC’s updated recommendations for isolation and quarantine balance what we know about the spread of the virus and the protection provided by vaccination and booster doses,” CDC Director Rochelle P. Walensky, MD, MPH, said in a statement.

Rochelle Walensky

“These updates ensure people can safely continue their daily lives,” Walensky said. “Prevention is our best option: get vaccinated, get boosted, wear a mask in public indoor settings in areas of substantial and high community transmission, and take a test before you gather.”

The guidance was met with some criticism, including from experts who said the CDC did not place enough emphasis on testing.

Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security, said the updated recommendations reflect the virus’ new status as endemic.

Amesh A. Adalja

“It’s been clear for some time that a one-size-fits-all period for isolation did not fit the period of contagiousness. The updated guidance reflects the fact that this is going to be an endemic virus, and the disruption that a case causes can be safely minimized based on the enhanced scientific understanding that has accumulated,” Adalja told Healio.

“I am, however, unclear as to the differential quarantine recommendations for those boosted vs. those who are not,” he said. “I do not think it’s justified to treat those fully vaccinated as identical to those who have zero vaccine doses.”