Sarah Gilbert started working on a vaccine for Covid-19 just as soon as the virus genome was sequenced. Within weeks, she had a proof of principle. By early April, her team at the Jenner Institute in Oxford had manufactured hundreds of doses ready for use in clinical trials. In phase one of these trials, completed in July, this vaccine was shown to be safe for use in a thousand healthy volunteers, aged between 18 and 55. It also provoked exactly the kind of immune response to Covid-19 that Sarah was hoping to achieve. Larger scale clinical trials are currently underway in the UK, South Africa and Brazil. If everything goes according to plan and the vaccine meets all the necessary regulatory standards, it will be manufactured in multiple locations including the Serum Institute in India and made available for use in low to middle income countries. AstraZeneca has already committed to making two billion doses, each costing about $4. The UK has an order in for 100 million. Sarah talks to Jim Al-Khalili about her life and work. As a young woman, she nearly gave up on a career in science. Now she’s in charge of one the most successful vaccine projects in the world. How did Sarah and her Oxford team get so far, so fast in developing a vaccine against Covid-19?