The new recommendations look a lot like the regimen U.S. President Joe Biden followed after coming down with COVID last month. His precautions were stricter than controversial recommendations from the U.S. Centers for Disease Control and Prevention.

The study of 42 people with mild COVID, led by Imperial College in London and published Thursday in Lancet Respiratory Medicine Journal, was the first of its type to follow individuals in their communities versus a lab, according to the Academy of Medical Sciences. 

Participants were tested in their homes from before they came down with COVID through the time of infection to when they were no longer infectious, Professor Ajit Lalvani, director of the National Institute for Health and Care Research’s Health Protection Research Unit in Respiratory Infections at Imperial, said in a news release.

Researchers found that most people who are COVID-positive are not infectious before they develop symptoms—good news for those who care about protecting others from getting sick.

While the average length of infectiousness among participants was five days, many continued to shed virus after that period, and some were still shedding virus at seven days, according to researchers.

Because of this, recommendations are as follows:

• Isolate five days from the time your symptoms begin. 
• Take an at-home test on your sixth and seventh days. If both tests are negative, you can leave isolation.
• If a person continues to remain positive or doesn’t have access to at-home tests, they should wait until day 10 to leave isolation.

Legal versus ethical advice

“Self-isolation is not necessary by law, but people who want to isolate need clear guidance on what to do,” Lalvani said in the release.

The National Health Service in London recommends a five-day isolation starting from the day after a positive test. Per new guidelines released in the U.S. earlier this month by the Centers for Disease Control and Prevention, individuals who test positive for COVID should isolate for five days, with Day 1 being the first full day after symptoms start—or the first full day following testing, if no symptoms are present.

Isolation can end on day five for those with no symptoms, according to the CDC. Those who had symptoms can leave isolation on day five as long as they’ve been fever-free for 24 hours without using fever-reducing medication and their symptoms are improving.

But such isolation regimens may not be sufficient to prevent further spread of the disease, Lalvani said.

“Our data suggests that under a crude five-day self isolation period, two-thirds of cases released into the community would still be infectious,” though they’re likely less infectious than they were earlier in their illness, he said.

The authors cautioned that the study was completed before Omicron, and that currently circulating variants may have a lower viral load and shed for a shorter length of time. Additionally, most study participants were healthy, white, middle-aged individuals who were not obese and had no preexisting health conditions. 

Individuals who aren’t as healthy may be slower to clear the virus, the authors caution.

Similar to Biden’s routine

The CDC’s recommended isolation time was 10 days until December, when the federal health agency halved it. Some scientists have questioned the rationale behind the policy change. Viral shedding can occur beyond 10 days even in healthy, vaccinated adults, according to a preprint out of London published in July. And “there is not data to support five days or anything shorter than 10 days” when it comes to isolation, Amy Barczak, a physician at the Massachusetts General Hospital Infectious Disease Division, recently told Nature.

Even before the London study’s release, some scientists advised that people stop quarantining only once they test negative using at-home tests, rather than relying on the CDC’s five-day rule alone. That’s what Biden did when he came down with COVID last month, isolating for five days and testing negative at days five and six before ending isolation—and repeating the routine when he tested positive again in a “rebound” case of the virus. He reportedly left isolation a day before London researchers would have recommended, though he still went above and beyond CDC guidelines.