The development of new vaccines for Covid 19 is a stunning scientific achievement. But now we some a cunning plans to get them out of their vials and into billions of arms around the world. Different strategies are being rolled out around the world, and like the virus itself, they are always evolving. In this episode of How To Vaccinate the World Tim Harford hears about vaccination strategies being rolled out in Indonesia and India and what the science tells us, and doesn't tell us, about who should be first in the queue. Listener questions for future episodes can be sent to vaccine@bbc.co.uk.

Producers: Sandra Kanthal and Josephine Casserly