December 28, 2021
The U.S. Centers for Disease Control and Prevention has shortened the recommended isolation time for people with asymptomatic COVID-19 cases based on scientific data suggesting most infections occur early in the course of illness.
On Monday, the federal agency said people who test positive but remain asymptomatic only have to isolate for five days – instead of 10 – if they wear a mask around others for another five days.
People who test positive and develop symptoms may leave their homes after five days as long as they don't have a fever and their other symptoms are resolving, the CDC added. They also are advised to wear a mask for another five days.
Additionally, people exposed to the coronavirus only need to quarantine for five days – down from 10 – if they do not develop symptoms. Anyone who is fully vaccinated and boosted does not need to quarantine at all, but is advised to wear a mask for 10 days while around others.
"For all those exposed, best practice would also include a test for (the coronavirus) at day five after exposure," the CDC added. "If symptoms occur, individuals should immediately quarantine until a negative test confirms symptoms are not attributable to COVID-19."
Isolation relates to behavior after a confirmed infection, while quarantine refers to the time following exposure to the virus.
The updated guidelines are based on data showing most COVID-19 transmission occurs during the first two days before symptoms develop and in the 2-3 days afterward.
Data out of South Africa and the United Kingdom suggests the Pfizer-BioNTech and Moderna vaccines are only 35% effective against omicron infection, but a booster dose increases their effectiveness to 75%, the CDC said.
"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 Dr. Rochelle Walensky said in a statement. "These updates ensure people can safely continue their daily lives."