Covid: Why do some vaccines defend you for longer than others?

A measles vaccine can defend you for a lifetime. Tetanus provides you about 10 years of canopy, whereas flu vaccines want updating yearly. On the subject of Covid-19, we’re nonetheless undecided precisely how lengthy safety from the vaccine lasts.

BBC Well being and Disinformation Reporter Rachel Schraer explains why.

Movement graphics by Jacqueline Galvin.