The Centers for Disease Control and Prevention this week explained the scientific rationale for shortening its COVID-19 isolation and quarantine recommendations, and clarified that the guidance applies to kids as well as adults.
The CDC also maintained that, for people who catch COVID-19, testing is not required to emerge from five days of isolation — despite hints from other federal officials that the agency was reconsidering that.
The agency announced the changes last week, halving the isolation time for Americans who catch the coronavirus and have no symptoms or only brief illnesses. Isolation should only end if a person has been fever-free for at least 24 hours without the use of fever-reducing medications and if other symptoms are resolving, the CDC added.
It similarly shortened the time that close contacts need to quarantine, from 10 days to five.
CDC officials previously said the changes were in keeping with evidence that people with the coronavirus are most infectious in the two days before and three days after symptoms develop.
Some experts have questioned how the new recommendations were crafted and why they were changed amid a spike in cases driven largely by the highly contagious omicron variant. Some also expressed dismay that the guidelines allowed people to leave isolation without getting tested to see if they were still infectious.
On Tuesday, the CDC posted documents designed to address those — and other — questions about the latest recommendations. The new guidance applies to school children as well as adults, the CDC said, responding to questions raised by school leaders around the country.
In laying out the scientific basis for the revisions, the agency said more than 100 studies from 17 countries indicate that most transmission happens early in an infection. The CDC acknowledged the data come from research done when delta and other pre-omicron variants were causing the most infections. But the agency also pointed to limited, early data from the U.S. and South Korea that suggests the time between exposure and the appearance of symptoms may be shorter for omicron than for earlier variants.
The CDC also took up the question of why it didn’t call for a negative test before people emerge from isolation.
The agency said lab tests can show positive results long after someone stops being contagious, and that a negative at-home test may not necessarily indicate there is no threat.