We delve into the science of how some vaccines could have unexpected effects beyond their intended target. They are called “non-specific effects” and we are only just at the beginning of our understanding despite scientists documenting this curious biological phenomenon more than 100 years ago.

One of the earliest vaccines to be studied was the Bacillus Calmette-Guérin vaccine for Tuberculosis, better known as the BCG. Professor Christine Stabell-Benn gives us a history lesson and brings us up to date with her team’s research at the Bandim Health Project in Guinea-Bissau, Western Africa.

Our studio guest this week is BBC News health and science journalist Philippa Roxby who talks us through the latest after an 11-year-old girl in Cambodia died from the H5N1 strain of bird flu. Plus, we look at new studies on long Covid and how much exercise we should be aiming to do each day.

Presenter: Claudia Hammond