What is COVID rebound? Paxlovid treatment could present positive test results days later

Posted at 9:56 AM, Jul 31, 2022
and last updated 2022-07-31 10:09:49-04

TAMPA, Fla. (WFTS) — Just days after testing negative for COVID-19, President Joe Biden said he's tested positive once again.

"I tested positive this morning, going to be working from home for the next couple of days," President Biden said in a video posted to social media Saturday night.

President Biden is in a small minority of people who experienced COVID-19 rebound after taking Paxlovid, an antiviral pill for the disease.

Paxlovid is supposed to help the body get rid of COVID-19 quickly. A Pfizer clinical trial found the pill lowered the risk of hospitalization or death among high-risk COVID patients by 88%.

University of South Florida Professor Dr. Thomas Unnasch said the problem here is the drug's longevity.

"It is probably the most effective antiviral we have right now against COVID-19," he said.

The pill works by preventing COVID protein from attaching to form a virus capsule.

"What Paxlovid is doing is essentially making it impossible for (COVID) to cut all its little pieces together so that it can put them together into a virus particle," he added.

He said despite being the best antiviral, it's not perfect.

"It's unfortunate that Joe Biden got it. But I can say I've known of four people who have taken Paxlovid, and one out of the four people ended up with COVID rebound, just like Joe has gotten. So, it may be a higher level of rebounding that we're actually seeing initially from the clinical trials," said Dr. Unnasch.

He said about 5% of the people who take the drug see COVID rebound two or three days later.

"Probably one of the reasons for that is that the drug itself is not really very stable in our bodies. So, it actually is given with another drug that tries to increase the longevity of the time that it stays within the body. Because normally, if you give it just by itself, it won't last for hours in the body. And so you know, when you take it, you'll get a nice peak of the drug. But as soon as you stop taking it, the drug disappears." he said.

If you test positive again, isolation is recommended. However, this doesn't mean that you've been reinfected with the virus.

"Reinfection sort of suggests that you had taken the drug, you were cured, and you got exposed to the virus again, and you got a second infection. You're clearing the virus, but you never clear it all the way. So, when you stop taking the drug, it just comes back."

Dr. Unnasch said there are still other ways to fight the virus, like monoclonal treatments.

"They're just two different types of treatment for the same COVID infection. And I think you could really choose one or the other, whichever shield is out there. Now they're using that as a good preventative for people who didn't develop a good immune response when they got vaccinated, who are immunocompromised or for whatever reason, and it's an alternative treatment."

Monoclonals have to continuously adjust as the virus mutates. That's also a possibility for Paxlovid.

The CDC has not yet determined if patients with COVID Rebounds are more or less likely to spread the virus than they were during their initial illness.

As for President Biden, he said, "I'm feeling fine, everything's good, but Commander and I got a little work to do."