President Joe Biden experienced a “rebound” Covid infection after taking the antiviral drug Paxlovid – and he’s not alone.
Some patients who took Pfizer’s Paxlovid after contracting the coronavirus have reported the same phenomenon: Days after completing a five-day course of the oral drug and feeling better, their Covid symptoms or a positive test result returned.
Health experts say Paxlovid’s rebound effect won’t affect every patient or make it less effective at its job, which is fighting serious illness from Covid. Still, as with so much about the pandemic, you may have some questions: How serious are rebound cases? Why do they happen? How common are they and do you still need to feel comfortable taking the drug?
The answer to that last question is a resounding “yes,” doctors say. Here’s why and what else you should know about Paxlovid rebound cases:
Who can use Paxlovid?
In December 2021, the U.S. Food and Drug Administration made Paxlovid available under an emergency approval for the treatment of mild to moderate Covid cases in a specific group of eligible patients. You can get Paxlovid if you check all three of these boxes:
- You have tested positive for Covid
- You are at least 18 years old, or at least 12 years old and weigh at least 88 pounds
- You have one or more risk factors for severe Covid
That includes patients 65 and older — like Biden, 79 — or those with underlying conditions such as cancer, diabetes or obesity. According to the FDA, you may not be able to take Paxlovid if you are taking certain medications that can interact with the drug and cause serious side effects.
You can obtain Paxlovid prescriptions from your health care provider or through the Biden administration’s “Test to Treat” program, which gives free Covid antiviral pills to patients who test positive at pharmacies across the country.
If you are eligible, you should start taking Paxlovid as soon as possible after testing positive for Covid and within five days of experiencing Covid symptoms. You must take three pills twice a day for five days.
Pfizer’s clinical trials from last November suggest that Paxlovid is doing its job: The drug was 89% effective in preventing hospitalization in people at risk of developing serious illness.
Notably, that trial was conducted before the omicron variant of Covid emerged — but Pfizer said in January that Paxlovid is still working against omicron, citing three lab-based studies. According to Barbara Santevecchi, a clinical assistant professor of infectious diseases at the University of Florida’s College of Pharmacy, it also appears to work against omicron subvariants such as BA.5, without the current data showing otherwise.
How common are rebound cases and what are they like?
Some people who take Paxlovid test negative for Covid after finishing their five-day treatment, but then test positive or experience symptoms again two to eight days later, according to the Centers for Disease Control and Prevention.
About 5% of the tens of thousands of Paxlovid users have experienced rebound cases to date, said Dr. Ashish Jha, White House Covid Response Coordinator, at a press conference last month. They appear to be very mild: A June CDC survey found that less than 1% of patients taking Paxlovid were admitted to the hospital or emergency department in the five to 15 days after they finished treatment. for Covid.
Patients also seem to recover from rebound cases without any additional Covid treatment, the CDC says.
A UC San Diego School of Medicine study released in June identified “inadequate drug exposure” as the most likely cause. In that scenario, Paxlovid stops the virus for five days, but doesn’t hang around long enough to completely clear the infection — allowing the virus to temporarily replicate again once the drug wears off.
dr. Davey Smith, the study’s lead author and infectious disease specialist at UCSD Health, hypothesizes that some people may be able to metabolize Paxlovid more quickly, or that the drug may need to be taken more than five days to completely clear the virus in each patient. But there’s no clinical data to back that up yet, he says.
“We don’t know if it’s safe or effective to do twice as much time as Paxlovid, taking two courses,” Smith tells CNBC Make It. “That’s going too far on your skis without the clinical research to guide it.”
If you experience a rebound case, you will need to quarantine again until you test negative again. The CDC recommends insulating for at least another five days before checking the agency’s current isolation guidelines. You should also wear a mask for 10 days after rebound symptoms start, the CDC advises.
Do I still need to take Paxlovid if I’m eligible?