How dogs have become a secret weapon in the battle to detect and combat COVID-19

With each passing day - the number of people who've been vaccinated for Covid-Nineteen gets ever larger. One thing scientists don't know is whether people may still carry the virus - but not show any symptoms - after receiving their jabs. So - testing will be vitally important - and scientists are looking for help in a familiar place - as the BBC's Tim Allman explains.