Over 20% Covid-infected people taking Paxlovid experience viral rebound: Study

New Delhi: One in five Covid-infected people being treated with antiviral medication Paxlovid tested positive after an initial negative test result, and they were also found to be shedding live and potentially contagious virus that could make others ill, according to a new new study.

The findings imply the patients’ potential for a viral rebound and disease transmission after initial recovery, they said.

People not taking Paxlovid experienced the viral rebound phenomenon only about two per cent of the time, the researchers at the Mass General Brigham hospital, Boston, US, found.

Paxlovid, which is a Nirmatrelvir-ritonavir therapy taken orally, has been previously studied to be effective in reducing hospitalisation and death in severe COVID-19 infections.

‘We conducted this study to address lingering questions about Paxlovid and virologic rebound in COVID-19 treatment,’ said corresponding author Mark Siedner, M.D., MPH, an infectious disease clinician and researcher in the Division of Infectious Diseases at Massachusetts General Hospital. ‘We found that the virologic rebound phenomenon was much more common than expected -- in over 20 per cent of people taking Paxlovid -- and that individuals shed live virus when experiencing a rebound, implying the potential for transmission after initially recovering from the virus.’

This study, being an observational one and not a randomised clinical trial, could not ascertain if solely the use of Paxlovid caused the increased rebound rate in patients, the researchers said in their study published in the journal Annals of Internal Medicine.

However, they said that their findings should not discourage clinicians from prescribing the medication, but should

prompt them to counsel patients about the risk for viral rebound and potential transmission while taking the medication and to advise them to re-test and isolate, should this happen. ‘Paxlovid remains a life-saving drug I prescribe to high-risk patients,’ said co-senior author Jonathon Li, an infectious disease physician and researcher at the hospital.

‘This study, while informative, does not change the fact that this drug is

very effective at preventing hospitalisations and death.

Instead, it offers valuable insights to Paxlovid patients, helping them understand what to expect and how long they might be contagious,’ said Li.

For the study, the researchers at the hospital-based research institute selected 142 individuals

between March, 2022 and May, 2023 based on positive COVID-19 tests, medication prescriptions or physician referrals.