AstraZeneca's pause of an experimental vaccine for the coronavirus after the illness of a participant 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."
Governments are desperate for a vaccine to help end the Covid-19 pandemic, which has caused more than 900,000 deaths and global economic turmoil, and the WHO had flagged AstraZeneca's, being developed with Oxford University, as the most promising.
However, the drugmaker suspended late-stage trials on its potential vaccine this week after a participant in Britain was reported to be suffering from symptoms associated with a rare spinal inflammatory disorder.
"It's a race against this virus, and it's a race to save lives. It's not a race between companies, and it's not a race between countries," added WHO's head of emergencies Mike Ryan.
More than 27.95 million people have been reported infected globally, according to a Reuters tally.
WHO epidemiologist Maria Van Kerkhove said there were a combination of factors helping reduce death rates in Europe, including finding cases earlier and clinical care.
"We know that early intervention at the first point of entry ... will save lives. In addition, we are in a better position to prevent the virus from infecting vulnerable populations," she said, cautioning, however, that the long-term effects of the disease were still not known.