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An experimental pill to treat Covid developed by the US company Pfizer cuts the risk of hospitalisation or death by 89% in vulnerable adults, clinical trial results suggest.

The drug – called Paxlovid – is aimed at the elderly and others at high risk of severe disease.

It comes a day after the UK medicines regulator approved a similar treatment from Merck Sharp and Dohme (MSD).

Pfizer says it stopped trials early as the initial results were so positive.

The UK has already ordered 250,000 courses of the new Pfizer treatment along with another 480,000 courses of the MSD pill.

The Pfizer drug, known as a protease inhibitor, is designed to block an enzyme the virus needs in order to multiply. It works slightly differently to the Merck pill which introduces errors into the genetic code of the virus.

Pfizer said it plans to submit interim trial results for its pill to the US medicines regulator, the FDA, as part of the emergency use application it started last month.