In a new guideline released earlier this week, the US health agency is shortening the recommended time for isolation from 10 days for people with Covid-19 to five days, if asymptomatic, followed by five days of wearing a mask when around others, Xinhua news agency reported.
The CDC has also updated its recommendation of quarantine period for those exposed to Covid-19. For people who are unvaccinated or are more than six months out from their second mRNA dose or more than 2 months after the Johnson & Johnson vaccine, and not yet boosted, the agency recommends quarantine for five days followed by strict mask use for an additional five days.
The change in guidance was “motivated by science demonstrating that the majority of SARS-CoV-2 transmission occurs early in the course of illness,” according to the health agency.
CDC Director Rochelle Walensky said the change was also motivated by economic and societal concerns.
“With a really large anticipated number of cases from Omicron, we also want to make sure we can keep the critical functions of society open and operating,” she said on Tuesday.
“We can’t take science in a vacuum. We have to put science in the context of how it can be implemented in a functional society.”
The guidance does not require a negative test to leave isolation or quarantine, which experts worry may drive up transmission and new cases.
“CDC’s new guidance to drop isolation of positives to five days without a negative test is reckless,” tweeted Michael Mina, Assistant Professor of Epidemiology at Harvard T. H. Chan School of Public Health.
“Some people stay infectious three days, some 12 (days),” he tweeted.
“Test negative to leave isolation early is just smart.”
With the surge in cases driven by the Omicron variant, US President Joe Biden’s administration has faced criticism for failing to prepare adequate supply of tests. People are queueing up at malls and around city blocks, sometimes for hours, to get tested.
Another concern voiced by epidemiologists is that the new recommendation fails to distinguish between vaccinated and unvaccinated people, who recover from the virus at different times.
“Vaccinated people are much less likely to get infected and less likely to be infectious for a long period of time,” said Aaron Caroll, a pediatrician at Indiana University.
Eric Topol, Director of the Scripps Research Translational Institute, said the policy represents “a new low” for the CDC, saying it flies in the face of the Biden administration’s pledge to hew closely to scientific evidence to curb the pandemic.
Some experts are concerned there is not enough evidence of how Omicron behaves to support CDC’s new five-day isolation recommendation.
In the meantime, some other experts acknowledged that shortening the isolation period would relieve stress on hospitals and businesses as more workers become infected with Omicron.