Tedros Adhanom Ghebreyesus told a news briefing there was "no silver bullet at the moment - and there might never be".
Mr Tedros implored people around the world to comply with measures such as social distancing, hand-washing and mask-wearing, saying: "Do it all."
Globally, more than 18 million Covid-19 infections have been recorded.
The death toll stands at 689,000, with both figures given by the US-based Johns Hopkins University.
Speaking from its headquarters in Geneva, the WHO chief said work on immunisation was progressing.
"A number of vaccines are now in phase 3 clinical trials, and we all hope to have a number of effective vaccines that can help prevent people from infection.
"However, there is no silver bullet at the moment, and there might never be," Mr Tedros warned. "For now, stopping outbreaks comes down to the basics of public health and disease control: testing, isolating and treating patients, and tracing and quarantining their contacts."
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