A blockbuster drug developed by US pharmaceutical group Merck to treat Covid-19 has been linked to mutations transmitted when the coronavirus spreads between patients, a finding that will increase scrutiny about its usefulness and the billions spent by governments on its procurement.
Researchers analysed a family tree of 15mn sequences of coronavirus to see which mutations had occurred and when, with the results showing they increased in 2022 after molnupiravir, which is also known by the trade name Lagevrio, was introduced in many countries.
The mutations were also more likely to be seen in older age groups and people more at risk of severe disease who were taking molnupiravir, and in countries where the antiviral treatment was more widely used.