The agency issued a notice on Tuesday, after reports emerged in recent months that those who received the drug where having their symptoms return after they finished treatment – even after feeling fully healed at some points.
Paxlovid is believed to be the most effective treatment against the virus, and has been a favorite of the White House in recent months – with President Joe Biden even making it available for free to all infected people.
Clinical trials showed it could reduce likelihood of hospitalization or death from infection by 90 percent if taken within days of symptoms first appearing, though some fear the protection may not be long-lasting.
The CDC has issued a warning that some recipients of Pfizer’s antiviral Covid pill Paxlovid may suffer symptoms of the virus once again after infection (file photo)
‘Paxlovid continues to be recommended for early-stage treatment of mild to moderate COVID-19 among persons at high risk for progression to severe disease,’ the CDC wrote in the notice.
‘…A brief return of symptoms may be part of the natural history of SARS-CoV-2 (the virus that causes COVID-19) infection in some persons, independent of treatment with Paxlovid and regardless of vaccination status.’
Experts are not sure why this is occurring, or what could be causing a person that is seemingly fine to later start feeling sick against from the same infection.
‘We had three cases in the house with the same pattern,’ John Donoghue, 71, told the Boston Globe about the mysterious phenomena last month.
‘The symptoms the second time were milder … in some ways, we feel that Paxlovid did its job. It took away the extreme symptoms of the first round and reduced them very quickly in all three cases.’
He reported that he, his wife and is mother, 95, all began to take the drug after contracted Covid.
Each started to feel better after using Paxlovid, but and even began to test negative, before their symptoms and positive test status returned once again.
The drug was widely touted by the White House as the best treatment for someone already infected by the virus (file photo)
Dr Paul Sax, an infectious disease expert at Brigham and Women’s Hospital in Boston, told the Globe he had heard about the same occurring in patients as well.
‘We continue to monitor data from our ongoing clinical studies and real-world evidence. We have not seen any resistance to Paxlovid, and remain very confident in its clinical effectiveness,’ Pfizer told DailyMail.com when asked for comment.
The drug’s arrival was met with fanfare among health and pharmacy experts across the world because of its successful trials.
It received Emergency Use Authorization from the Food and Drug Administration in late 2021.
While the New York City-based company initially ran into supply issues, hindering the rollout early on, there is reportedly an excess of the drug available in the U.S. at the moment.
‘It’s important to recognize treatments available today for COVID-19 have provided a real game-changer in the global efforts to halt the devastation of the pandemic,’ the company wrote in an email to DailyMail.com in April.
‘Our trials and real-world evidence demonstrated that the treatment has the potential to save patients’ lives, reduce severity of infections and eliminate up to nine out of ten hospitalizations.’
Excitement for the drug was so high that President Biden even spoke of it at his State of the Union address earlier this year, and said that any American that needed the drug would have access to it.
Some of those patients that did receive the drug are now reporting oddities with their infections after taking the drug, though.
Experts told the Globe that the likely mechanism at play for the Donoghues, and others who have experienced similar phenomena can be described as a game of cat and mouse.
‘It’s literally that the Paxlovid is the cat, it suppresses the virus, and then when the cat’s gone, the mice come out to play,’ Dr. Michael Charness, chief of staff at Veterans Affairs Boston told the Globe.
‘Paxlovid works really well while it’s there, and for many people, they can eliminate the virus in a single phase of infection,’
‘But for some people, maybe because it takes a little longer to ramp up immunity, they can’t get rid of [all the virus] and the Paxlovid is no longer there to help.’