So, after much waiting and hoping, a Covid 19 vaccine has been approved for use in the UK. Now the roll out begins. But, it’s not easy moving around a vaccine that has to be stored at temperatures of an Antarctic winter, or organising two doses of the jab for the most vulnerable people around the country. On this week’s How To Vaccinate The World, Tim Harford talks with a group of experts about the complicated logistics of a vaccination programme being worked out in real time. Programme producers: Sandra Kanthal and Josephine Casserly