What is blood plasma and how does it treat Covid-19?

Scientists are looking at whether plasma in human blood could be used to treat people who are seriously ill with Covid-19.

Health services around the world have been asking for people to donate plasma for covid patients to find out how effective the treatment is.

It's all to do with antibodies found in the blood - but what's the science behind the process?

BBC health correspondent Laura Foster explains

Video by Mattea Bubalo, Laura Foster and Terry Saunders.