The World Health Organization warned on Monday that while there were strong hopes for a COVID-19 vaccine, there might never be a "silver bullet" for the coronavirus that has infected millions around the world.
"There is no silver bullet at the moment and there might never be," director-general Tedros Adhanom Ghebreyesus told a virtual news briefing from the UN body's headquarters in Geneva.
The number of coronavirus cases recorded worldwide topped 18 million on Monday.
Six months after the WHO declared a global emergency, the virus has killed more than 687,000 people since it first emerged in China late last year, according to an AFP tally compiled from official sources.
Fresh clusters have been reported in countries that had previously brought their outbreaks under control, forcing governments to reimpose lockdown measures despite worries over further economic fallout.
Ghebreyesus and WHO emergencies head Mike Ryan exhorted all nations to rigorously enforce health measures such as mask-wearing, social distancing, hand-washing and testing.
"The message to people and governments is clear: 'Do it all'," Tedros said, adding face masks should become a symbol of solidarity round the world.
Ryan said countries with high transmission rates, including Brazil and India, needed to brace for a big battle: "The way out is long and requires a sustained commitment."
