It is one thing to design and test covid-19 vaccines. It is another to make them at sufficient scale to generate the billions of doses needed to vaccinate the world’s population. How are the vaccines produced, why is production so variable and will it meet demand this year? We speak to Adar Poonawalla, CEO of the Serum Institute of India, the world's biggest supplier of vaccines. The Economist’s technology correspondent Hal Hodson explains why some vaccines take longer to produce than others. James Fransham from our data team discusses when supply will meet demand. Alok Jha, The Economist's science correspondent, hosts with our health policy editor, Natasha Loder. Oliver Morton, The Economist's briefing editor, joins them. For full access to The Economist’s print, digital and audio editions subscribe at economist.com/thejabpod. Sign up for our new weekly science newsletter at economist.com/simplyscience and data newsletter at economist.com/offthecharts   See acast.com/privacy for privacy and opt-out information.