June 4 (Reuters) - Britain’s medicines agency has approved an extension of Pfizer and partner BioNTech’s COVID-19 vaccine for use in children as young as 12, it said on Friday, a week after a similar clearance was given by European authorities. (Reporting by Pushkala Aripaka in Bengaluru; Editing by Arun Koyyur) Our Standards: The Thomson Reuters Trust Principles.