Seven centres begin operating this morning across England, a key part of efforts to vaccinate 15 million in the top four priority groups by mid-February. To begin with, more than 600,000 aged 80 or over are being sent letters inviting UK’s them to book an appointment at one of the hubs – but if the journey is too long, they’re being told closer options ill be available soon. The centres will be open 12 hours a day and more large-scale sites will follow. The health secretary will give more details later, while the Welsh government will publish its own vaccination plan. In Scotland, more clinics should start to receive the Oxford/AstraZeneca vaccine. Here’s how vaccines are approved for use, and some of the challenges a rollout on this scale faces.