Safety of a prospective Covid-19 vaccine comes “first and foremost”, the World Health Organisation’s chief scientist has said, as a trial of a leading candidate from AstraZeneca was paused due to concerns over side effects.

“Just because we talk about speed [...] it doesn’t mean we start compromising or cutting corners on what would normally be assessed,” Reuters quoted Dr Soumya Swaminathan as saying.

“The process still has to follow through rules of the game. For drugs and vaccines which are given to people, you have to test their safety, first and foremost,” she said.