• Covid patients who use Paxlovid are twice as likely to suffer an infection rebound
• In a study, a third of patients who used the drug had their Covid return 
• It is yet another setback for the drug President Biden backed in March
• The CDC warned about these Covid rebounds when reports emerged in May 

Authors: MANSUR SHAHEEN DEPUTY HEALTH EDITOR FOR DAILYMAIL.COM PUBLISHED: 12:32 EST, 17 November 2022

People appear to be more likely to suffer a Covid rebound if they use Pfizer‘s antiviral drug Paxlovid, a study suggests.

In the past few months, President Joe Biden, Dr Anthony Fauci and CDC director Dr Rochelle Walensky have all tested positive again quickly after they stopped taking the drug.

Scientists from Scripps Research Translational Institute in La Jolla, California, compared 127 infected people who used Paxlovid to 43 others who beat the virus without the drug.

They found that 14 per cent of Paxlovid users tested positive for the virus in the weeks after recovering. Meanwhile, only nine per cent tested positive again in the group that didn’t use the antiviral. 

The study was small and the researchers don’t feel confident that the results weren’t chance, but they aim to stand it up in a future trial involving 800 people.

The exact causes of the rebound are unknown, but doctors suspect it is because of the how the drug functions. Rather than killing the virus outright, Paxlovid stop its replication within the body. 

Experts theorize that, having been suppressed by Paxlovid, Covid bounces back when the drug vanishes from the body, leading to high viral levels and potent immune responses that can cause symptoms to reappear. 

Notable examples of the Covid rebounds include President Joe Biden, who suffered a rebound after being infected with the virus in June and receiving Paxlovid

Two of America’s leading health officials, Dr Fauci, the nation’s top infectious disease expert, and Dr Walensky, director of the Centers for Disease Control and Prevention (CDC), were also affected.

The drug was heralded by President Biden as one of the silver bullets to fight the pandemic at his 2022 State of the Union address.

Paxlovid was central to his ‘test to treat’ Covid program launched earlier this year that offered it to Americans who tested positive for the virus at select pharmacies.

It is prescribed as three pills taken twice a day for five days 

The study, which is available in pre-print and still pending peer review, gathered data from 170 patients.

Each of the patients were offered Paxlovid after testing positive for the virus. Among them, 127 accepted to offer while 43 chose not to use the drug.

Patients were also given 12 at-home COVID-19 tests and instructed to test themselves every other day. 

They reported test results and daily symptoms to researchers.

In the weeks following completion of the course, 18 people in the Paxlovid group, or 14 per cent, once again tested positive for the virus.

Another 22, or 19 per cent of the study group, reported that their Covid symptoms had returned but did not record a positive test.

In the control group, only four testes positive again – nine per cent – while three had symptoms return despite negative swabs – or seven per cent.

In total, 33 per cent of Paxlovid users and 16 per cent of non-users experienced either a symptom bounce back or positive test after recovering from virus. 

Dr Michael Charness, chief of staff at the Veterans Affairs Boston Healthcare System, told CNN: ‘There is an indication that symptomatic rebound is more frequent in Paxlovid-treated participants than in untreated controls, but larger numbers are needed to draw confident conclusions.’

This study is another setback for Paxlovid, which was billed as a pandemic ‘game-changer’ when it first hit the market in late 2021.

Clinical trials showed it reduced the likelihood of hospitalization or death caused by the virus 90 per cent.