WHO's Nabarro: Vaccine roll-out 'enormously challenging'

World Health Organization (WHO) special envoy on Covid-19, David Nabarro, says there are still a number of challenges ahead in getting coronavirus vaccines distributed around the world.

Dr Nabarro told BBC World News: "The manufacturers are still getting up their systems for dispatch to governments and then governments are getting up their systems of dispatch. There are going to be teething troubles.

"I don't want anybody to think this is an easy task. It is enormously challenging."

China announced on Monday that it will allow WHO experts into the country to investigate the origins of coronavirus.