Smitha Mundasad asks whether we will see waves of Covid – with infections going up and down and then up and down again - forever more. We speak to Elliot whose life has been transformed after a single shot of gene therapy to treat the inherited blood disorder haemophilia B. And Dr Margaret McCartney discusses the accidental discovery of Viagra and how sometimes researchers find new, surprising uses for old medicines.

Produced by Geraldine Fitzgerald.