Covid virus rebounds after ending treatment with Pfizer drug Paxlovid

Patients treated with the Covid-19 drug Paxlovid are reporting a disturbing after-effect in a development that could breed new variants.

Patients treated with the Covid-19 drug Paxlovid have had the virus return shortly after they cease taking the pill in a worrying development that could breed new variants.

US Government researchers are about to launch a study into the rebound effect after a single case was reported in a medical journal but more instances emerged on Twitter and on medical blogs.

Paxlovid is one of the main initial treatments for elderly and high-risk Covid patients in Australia and only recently was able to be prescribed by GPs.

The pill must be taken twice a day for five days and commenced as soon as possible after a Covid diagnosis.

Studies showed it cuts hospitalisation rates from Covid by 89 per cent and Australia has purchased 500,000 treatment courses.

US Columbia University Virologist David Ho told Bloomberg he caught Covid early last month, he took Paxlovid and within days of starting the treatment tested negative to the virus.

However, 10 days after first getting sick his symptoms returned. He sequenced his own virus and found both infections were the same strain.

Australian National University infectious diseases expert Professor Peter Collignon thinks Covid reinfection rate related to Paxlovid is likely rare.

Australian National University infectious diseases expert Professor Peter Collignon said the reinfections were likely relatively uncommon.

“It’s like taking an antibiotic for an infection and for most people it cleans it up but in some people it recurs because you haven’t necessarily killed all the bacterial viruses on the surface,” he said.

“That’s why sometimes you need to give a slightly longer course,” he said.

He suspects the reinfection rate is rare and if it was less than 1 per cent of people who get treated “I would not get overly concerned’.

However he said it was possible such reinfections might breed new variants of the virus and doctors needed to be judicious in using it.

“If you look at Tamiflu or other drugs, or for that matter, antibiotics, yes, it may happen and does occasionally, but it’s not a common event again,” he said.

“I think we do need to be judicious with this drug as we do for every other antiviral and antibiotic because if we overuse it, we get side effects for no great necessary benefit for the person. And you do probably increase the risk of resistance the more you use,” he said.

Paxlovid had a lot of side effects and interactions because it was designed to keep drugs active in the body for longer.

This meant if a patient was using other medications they could rise to toxic levels within the body, he said.

Originally published as Covid virus rebounds after ending treatment with Pfizer drug Paxlovid