GENEVA: AstraZeneca's pause of an experimental vaccine for the coronavirus after the illness of a participaint is a "wake-up call" but should not discourage researchers, the World Health Organization's (WHO) chief scientist said on Thursday.

"This is a wake-up call to recognise that there are ups and downs in clinical development and that we have to be prepared," Soumya Swaminathan told a virtual briefing from Geneva.

"We do not have to be discouraged. These things happen."