By Alistair Smout LONDON (Reuters) – Britain will expand access to Pfizer’s oral antiviral COVID-19 treatment to thousands more people by adding it to a trial to assess how best to use the drug in its highly vaccinated population, the health ministry said on Tuesday. Paxlovid, a combination of Pfizer’s new pill with an older antiviral ritonavir, was made available to thousands of people with compromised immune systems in Britain in February. Now Paxlovid is being added to the Panoramic national study in England, which is making antivirals available to a wide number of patients while collecting…