The key to fighting the coronavirus is stopping clusters spreading into community transmission, Dr Mike Ryan, head of the World Health Organization's emergencies programme, said on Thursday.
A very small percentage of the world population has had the virus already and it has a "long way to burn" if allowed, he said.
The WHO does not have enough information to make a judgement on the expanded use of the new Russian vaccine, Bruce Aylward, WHO senior adviser, said at the briefing in Geneva.
Russia on Tuesday became the world's first country to grant regulatory approval for a COVID-19 vaccine, to be named "Sputnik V" in homage to the Soviet Union's launch of the world's first satellite.
(Reporting by Stephanie Nebehay, Michael Shields and John Miller; Writing by Nick Macfie; Editing by Susan Fenton)
