What you need to know about COVID-19 rebound cases and what it means for isolation guidance

RALEIGH, N.C. (WTVD) -- President Joe Biden tested positive for COVID-19 again over the weekend. The positive test comes four days after he was cleared to leave isolation and nine days since he initially caught the virus.

Biden is now experiencing what health experts have coined a COVID-19 rebound case. COVID-19 rebound has started to occur in a small percentage of patients (around 1-2%) who were treated with Paxlovid.

Paxlovid is given to COVID-19 patients in the U.S who display mild-to-moderate symptoms and are at significant risk of progressing to severe illness. Clinical trials found the drug reduces a person's chance of going to the hospital by almost 90%.

Dr. Anthony Fauci also reported having a rebound case in June after he tested positive two weeks earlier and was prescribed Paxlovid. After his initial test, Fauci tested negative three days in a row but positive on the fourth day.

The CDC issued a health alert about the phenomenon at the end of May.

"COVID-19 rebound has been reported to occur between 2 and 8 days after initial recovery and is characterized by a recurrence of COVID-19 symptoms or a new positive viral test after having tested negative," the CDC wrote at the time.

While the agency had limited information at the time, it said there were no reports of severe disease with COVID-19 rebound cases. The CDC said in its alert that even patients with normal immune responses and were up to date with their vaccinations. It also said another round of treatment isn't needed.

"They may have a resolution of symptoms, tested negative and they have rebound symptoms, but that doesn't mean they need additional treatment," explained Wake County Medical Director Dr. Jose Cabanas. "Again, this is a small percent of cases, but it's important to follow up with your physician for any additional needs they may have at the time."

In May, the CDC claimed, "it remains unknown whether the likelihood of transmission during rebound differs from the likelihood of transmission during the initial infection."

The CDC suggested patients who experience COVID-19 rebound should restart isolation for at least another five days. Individuals can end the re-isolation if the fever has gone down for 24 hours without medication and overall symptoms are improving. The agency also recommends the patient wear a mask for a total of 10 days after rebound symptoms start.

Medical experts said that people who have a rebound case can transmit the virus to others even before redeveloping symptoms.

The CDC guidance continues to be that infected individuals regardless of their vaccination status should isolate for five full days (day 0 is the first day of symptoms or the date of the day of the positive viral test for asymptomatic persons). Isolation can end "if you are fever-free for 24 hours without the use of fever-reducing medication and your other symptoms have improved."

The CDC does not require individuals to test to get out of isolation.

"I think it's possible that someone's shedding the virus after 10 days. I think the CDC has looked into this and feels like the number of people that are still doing that is low enough that recommending universal testing with the rapid antigen test after the 10 days of isolation is not necessary," explained Dr. Jeffrey Jenks, the Durham County medical director.

Instead, the CDC recommends, "If an individual has access to a test and wants to test, the best approach is to use an antigen test1 towards the end of the 5-day isolation period."

While Cabanas said in most cases the risk of transmission is far lower after five days, he advises people to still test.

"From my perspective, it's actually a good practice if you have access to sort of test out of isolation and just get an antigen test, but the likelihood of transmitting the virus after those days is significantly less," Cabanas said. "Some patients have had a more complicated or more intense kind of disease process, They may need to have a longer period of isolation, but clinically, typically, they should be feeling better."

Jenks and Cabanas stressed that while Paxlovid is connected with these rebound cases, patients should still use the treatment.

"I absolutely don't think people should be concerned about taking Paxlovid even if there is a small chance of Paxlovid rebound. I think the advantages of taking Paxlovid far outweigh the side effect of getting a rebound, which is in a very small percentage of people," Jenks said.

He stressed that treatment still remains a key tool in preventing severe illness and death.

In North Carolina, more than 97,000 people have been administered the drug.

Find where you can get tested and receive treatment: https://covid19.ncdhhs.gov/FindTreatment