Explanation: Some patients reporting COVID rebounds after taking Pfizer pills

May 11 (Reuters) – More than 2.8 million courses of Pfizer Inc’s (PFE.N) oral COVID-19 antiviral treatment Paxlovid have been made available in pharmacies across the United States as the Biden administration works to improve access to medicine.

As Paxlovid has become more widely used, some patients have reported that COVID-19 symptoms return after completing treatment and experiencing improvement. Here is the latest information on these rebounds:

How common is a recurrence of COVID symptoms soon after treatment with Paxlovid?

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Dozens of people have reported a rebound of COVID symptoms on social media or to the U.S. Food and Drug Administration after taking Paxlovid, but Pfizer suggests the experience is rare.

Pfizer said that of the more than 300,000 patients it monitors who received the 5-day treatment, about 1 in 3,000 – around 0.03% – reported a relapse after taking the pills.

This is a lower rate than that seen by Pfizer in its Paxlovid clinical trial, where around 2% of participants experienced a rebound in viral levels after completing treatment.

The Pfizer trial suggested relapses may be a broader COVID trend, as a similar number of those who received a placebo also had viral load levels rebound.

Why do these recurrences occur?

The cause is not yet known. Some doctors have suggested that because the drug attacks the virus so quickly, some patients’ immune responses to COVID may be dampened, allowing the virus to replicate again. Others said there might be an as-yet-unidentified common characteristic among those who experience rebound.

Pfizer development director William Pao said it could be linked to the virus itself, not Paxlovid, since the phenomenon was seen in patients who received the drug and in those who did not. not received.

The US Food and Drug Administration also said it was unclear if the rebounds were related to Paxlovid.

Should I take a second course of Paxlovid after a rebound?

Not according to the FDA. He said last week there was no evidence of benefit for taking a second 5-day course of the pills or for a 10-day course.

Pfizer suggested otherwise. Chief Executive Albert Bourla said patients and doctors told Pfizer that a second five-day course of Paxlovid cleared the virus. Mikael Dolsten, the company’s chief scientific officer, recently said that some immunocompromised patients “can carry this virus for a very, very long time” and may need to take multiple courses or for an extended period of time.

The FDA stressed that the rebounds did not change Paxlovid’s ability to reduce hospitalizations and deaths.

Who is eligible for Paxlovid?

Eligibility for Paxlovid differs by country. In the United States, Paxlovid is licensed for patients at high risk of progression to severe COVID-19, whether vaccinated or not.

According to the US Centers for Disease Control and Prevention, these groups include anyone age 65 or older and people with risk factors such as obesity, diabetes, cancer, or use of immunosuppressive drugs. . Bourla estimated that half of American adults are eligible.

Does Paxlovid work against the long COVID?

Paxlovid is not licensed to treat the persistent and debilitating disease known as long COVID. However, there have been recent case studies of patients with long-term COVID who experienced symptom relief after taking Paxlovid. Read more

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Reporting by Michael Erman; Editing by Caroline Humer and Bill Berkrot

Our standards: The Thomson Reuters Trust Principles.

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