A pill for treating Covid-19 speeds up recovery but does not reduce hospitalisation or deaths in vaccinated adults at higher risk from the virus, according to UK research.
Earlier research had indicated that antiviral drug molnupiravir, produced by US multinational pharmaceutical company Merck, significantly reduced the risk of being admitted to hospital or dying from Covid-19.
When tested initially, molnupiravir — which prevents the virus from replicating — was found to be 30 per cent effective in reducing hospitalisations. However, that was for unvaccinated patients.
In November 2021, Britain became the first country in the world to approve molnupiravir for treating Covid-19.
In the latest research, led by University of Oxford researchers, nearly all of more than 25,000 patients in the study had received at least three vaccine doses.
Results demonstrate that vaccine protection is so strong that there is no obvious benefit from the drug in terms of further reducing hospitalisation and deaths, said study co-author Jonathan Van-Tam from the University of Nottingham.
The study, known as the Panoramic trial, was carried out in the winter of 2021-2022 when the Omicron variant was dominant.
The drug was, however, effective in reducing viral load and can help hasten patient recovery by roughly four days, researchers estimated.
Preliminary data from the study was unveiled in October. But the latest results offer more detail and have been peer-reviewed.
The study compared the oral pill against standard treatment alone in people over 50 and those aged 18 and older with underlying conditions. They had been unwell with confirmed Covid-19 for up to five days.
There might be circumstances in which molnupiravir could be useful, for instance, in under-pressure health systems where it could be used to help key workers back to work quicker, said co-chief study investigator Chris Butler from the University of Oxford.
But ultimately, those benefits need to be weighed against the drug's cost, said co-chief study investigator Paul Little from the University of Southampton.
Molnupiravir is estimated to cost several hundred pounds for a five-day course.
“For the moment, I think you have to say don't use this drug in the general population, including those at slightly higher-risk,” said Mr Little.
Following the study's publication, doctors in countries including Australia are reported be considering limiting the use of molnupiravir.
The treatment generated almost $5 billion in sales for Merck in the first three quarters of 2022.
Last month, Britain's National Institute for Health and Care Excellence recommended against the use of molnupiravir at current prices, due to concerns about cost-effectiveness.