People who rebound with COVID-19 after Paxlovid may be highly contagious, new studies show – The Boston Globe

People who rebound with COVID-19 after Paxlovid may be highly contagious, new studies show - The Boston Globe
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The CDC warning cited recent reports from researchers documenting some Paxlovid rebounds, including among patients who were vaccinated and boosted.

The CDC warning comes as two small but provocative new studies by different teams of researchers in Boston and New York suggest such relapses may not be so unusual. The scientists also found that, in some rebound patients, viral levels were likely high enough to be contagious.

Besides, a study found that two patients who have inadvertently relapsed infected family members. In one case, a 67-year-old man with no symptoms six days after completing Paxlovid infected a 6-month-old family member. The transfer took place after the CDC’s suggested time window for isolation.

“It’s not uncommon, otherwise why do we see these clusters?” said Dr. Michael Charness, chief of staff of the VA Boston Healthcare System and co-lead author of the study, which analyzed COVID infections in 10 patients, ages 31 to 71, who were fully vaccinated and received at least a reminder. The study was posted Monday and has not been peer reviewed.

Paxlovid is a home treatment prescribed at the first signs of infection to patients at high risk of serious complications from COVID. The treatment consists of a total of 30 pills – three pills taken twice a day for five days.

When the manufacturer Paxlovid Pfizer received emergency use authorization for the drug in December with federal regulators, his data showed that about 2% of patients in his trial experienced a rebound, as did about 1.5% of those who received a placebo.

The Charness study does not directly refute Pfizer’s data, but suggests that bounces are more common. Patients in this study experienced relapse symptoms beginning between three and eight days after completing Paxlovid, and symptoms lasted between three and ten days.

Antigen tests performed while the patients relapsed indicated that they remained positive for a median of six days and up to day 18 after their initial positive pre-Paxlovid test.

For comparison, the Charness group looked at a separate group of COVID patients who hadn’t taken Paxlovid: nearly 1,000 National Basketball Association staff. None had a relapse of COVID. They have not published this data.

“We cite the NBA data to say that this is clearly different from what was observed” by Pfizer, said Dr. David Ho, director of the Aaron Diamond AIDS Research Center at Columbia University and co-author Charness and NBA studies.

A Pfizer spokesperson said the company continues to monitor data from its ongoing studies of Paxlovid, as well as reports rebound doctors and patients. He said all the data is “consistent with our observations” from the company’s drug trial.

The new CDC warning notes that a relapse of COVID with a brief return of symptoms “may be part of the natural history of infection with SARS-CoV-2 (the virus that causes COVID-19) in some people, regardless of Paxlovid treatment and regardless of vaccination status.

Federal data shows more than 668,000 courses of Paxlovid had been prescribed as of May 14. Doctors say that despite the rebounds, it was an effective drug that kept people at risk from going to hospital.

A second study by a team of Boston researchers analyzed seven patients who had rebounded from taking Paxlovid and found levels of live virus in three of them for up to nine days. One of the patient’s test samples showed live virus for 11 days after completing Paxlovid.

“It greatly increased the suspicion that they are contagious,” said Dr. Mark Siedner, an infectious disease clinician and researcher at Massachusetts General Hospital and co-author of the study, which has not been peer-reviewed. .

“It’s not just that they bounce back. It’s that they’re bouncing back and it looks like they’re starting all over again, their virus is skyrocketing,” Siedner said. “It’s a really unique phenomenon.”

Siedner’s team found no evidence that the virus had developed resistance to Paxlovid.

Siedner and other researchers say the rebound phenomenon raises urgent questions about whether patients should be treated with a longer course of Paxlovid or perhaps another drug.

The CDC alert does not definitively answer this question.

“There is currently no evidence that additional treatment is required with Paxlovid or other anti-SARS-CoV-2 therapies in cases where rebound COVID-19 is suspected,” he said. .

The rebounds with such high levels of live virus prompted Siedner to wonder if there is something about Paxlovid that could contribute to the phenomenon.

“That makes us wonder if we’re not using the drug correctly or for long enough, or is it something intrinsic about Paxlovid that doesn’t allow the immune system to kick in?” he said.

Siedner’s team, which includes researchers from Brigham and Women’s Hospital as well as the Broad Institute and Ragon Institute at MGH, MIT and Harvard, is launching a new study that hopes to answer some of these questions.

They will test the immune systems of people who have rebounded to see if the immune response of those who received Paxlovid is different from those who did not.

Dr. Kathryn Stephenson, an assistant professor at Harvard Medical School and an infectious disease physician at Beth Israel Deaconess Medical Center, also leads a Paxlovid studymonitoring patients who have just started the antiviral with COVID tests for two to three weeks to detect rebound information on symptoms.

She said hers and other small studies of a few dozen people are helpful, but much larger, rigorous studies are urgently needed to understand and treat rebounds.

“I think it’s Pfizer’s responsibility to produce and share this data quickly – it’s their medicine. [that received emergency use authorization,]“, said Stephenson.

“It’s not fair that clinicians and researchers are now trying to catch up and collect this data ourselves.”

Kay Lazar can be reached at Follow her on Twitter @GlobeKayLazar.

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