Prof Sarah Gilbert, Covid vaccine creator: Now let’s take on 12 more diseases

Vaccines are a bit like Goldilocks - they need to be kept at just the right temperature from the moment they're made to the moment they're given. It means there's a global network of freezers, fridges, cold boxes and so on, known as the cold chain. But it is hard to get vaccines to some of the remotest and poorest parts of the world, particularly where there is no electricity.