Coronavirus vaccines: Your questions answered

How many people do we need to vaccinate before we reach heard immunity? Why have we not used mRNA vaccines before? And will some countries find it harder to obtain the vaccines?

Prof Beate Kampmann from the London School of Hygiene and Tropical Medicine and Dr Deepti Gurdasani at Queen Mary University of London take viewers’ questions about the jabs.

Prof Kampmann and Dr Gurdasani were speaking to Lucy Hockings on BBC World News on Thursday.