On Tuesday, the Center for Disease Control and Preventions (CDC) disclosed its reasons for shortening the recommended COVID isolation period, citing more than 100 studies about timelines.
The agency announced the change in the previous week, decreasing the recommended isolation time to just five days for Americans who are infected with COVID and have no symptoms or only experience illness shortly. If a person has had no fever for a minimum of 24 hours without the use of fever-reducing medications and other symptoms are abating, isolation can end, the CDC said.
The amount of recommended quarantine time for those who have had close contact with someone who had COVID also decreased to five days from 10.
The CDC also said that testing is not required to end isolation. However, hints from federal officials appeared to show that the agency was reconsidering that.
The agency clarified Tuesday that the quarantine guidance is not only for adults but children, as well.
To show the scientific rationale for the changes, the CDC cited over 100 studies from 17 countries that found that a majority of transmissions occur early in an infection. While this data comes from research conducted when Delta and other COVID variants were the dominant strains, the agency also cited preliminary data from the U.S. and South Korea that seems to indicate that the time between exposure to COVID and the onset of symptoms may be decreased for Omicron compared to other variants.
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.
The CDC also took up the question of why it didn't call for a negative test before people emerge from isolation.
On Sunday, Dr. Anthony Fauci—the White House's top medical adviser—said the CDC was considering including the negative test as part of its guidance.
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. That's why, the agency said, it was recommending that people wears masks everywhere for the five days after isolation ends.
It did offer tips for those who have access to the tests and want to check themselves before leaving isolation.
Dr. Eric Topol, the head of the Scripps Research Translational Institute, accused the agency of furthering confusion. He agreed that it is appropriate to shorten isolation time, but only with testing.
"We do need to come up with a strategy that limits isolation time, but we don't want it to be one that's adding to the spread of the virus and unwittingly leading to the virus circulating," he said.
Yale University's Dr. Howard Forman said the updated recommendations were communicated poorly last week, but he also applauded the CDC for trying to be more nimble while dealing with limited science, a short supply of tests and an intensifying wave of infections.
Under the previous isolation and quarantine recommendations, "It was obvious that…society was literally going to be disrupted. If you expected people to comply with those (old) rules, you might as well have a lockdown," said Forman, a radiologist who teaches public health policy.
The agency acknowledged people weren't following the longer recommendations: Research suggests only 25% to 30% of people were isolating for a full 10 days under the older guidance, the CDC said.
The CDC also suggests that people exposed to the virus quarantine for five days, unless they have gotten booster shots or recently received their initial vaccine doses. The agency said anyone exposed—regardless of vaccination status—should get tested five days later, if possible.
The Associated Press contributed to this report.
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