"It is important to put this on the table: this virus may become just another endemic virus in our communities, and this virus may never go away," Dr Ryan told the virtual press conference from Geneva.
"HIV has not gone away - but we have come to terms with the virus."
Dr Ryan then said he doesn't believe "anyone can predict when this disease will disappear".
There are currently more than 100 potential vaccines in development - but Dr Ryan noted there are other illnesses, such as measles, that still haven't been eliminated despite there being vaccines for them.
WHO Director-General Tedros Adhanom Ghebreyesus stressed it was still possible to control the virus, with effort.
"The trajectory is in our hands, and it's everybody's business, and we should all contribute to stop this pandemic," he said.
WHO epidemiologist Maria van Kerkhove also told the briefing: "We need to get into the mindset that it is going to take some time to come out of this pandemic."
https://www.bbc.co.uk/news/world-52643682