WHO Director-General Tedros Adhanom 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, Al-Jazeera reported.
"The message to people and governments is clear: 'Do it all'," Tedros told a virtual news briefing from the UN body's headquarters in Geneva.
He said face masks should become a symbol of solidarity round the world.
"A number of vaccines are now in phase three clinical trials and we all hope to have a number of effective vaccines that can help prevent people from infection. However, there’s no silver bullet at the moment - and there might never be," he added.
More than 18 million people around the world have been diagnosed with the new coronavirus as of Monday. Almost 11 million have recovered and while nearly 690,000 have died.