The UK approach to COVID-19 vaccination: why was it so different?

The vaccination campaign in the United Kingdom has been extremely successful. Bold decisions were made to order vaccines early, before we knew if they would be effective, and to vary from the manufacturers' recommendations by extending the 'prime-boost' interval between the first and second doses of the AstraZeneca and Pfizer-BioNTech vaccines. These decisions were controversial at the time but have contributed enormously to the effectiveness of the vaccination programme.