Vaccines are formidable tools against infectious disease. But the success of a vaccine in one part of the world doesn't guarantee similar outcomes elsewhere. That's where human infection studies come in – where volunteers, closely monitored by researchers, receive a vaccine and are subsequently given a small dose of an infectious disease. This might sound worrying, but it is a quick and effective way to get data about whether a vaccine is working.

Alisha speaks with Dr Dingase Dula, who researched a pneumococcal vaccine in Malawi, to learn more about the impact of infection studies. They also meet Becky Mkandawire and Stonard Mwale, who volunteered to take part in the study. They discuss the role of trust in human infection studies, what it's like to be part of one, and the importance of African-led research in combating infectious disease.