Speaking at a briefing on Wednesday, WHO emergencies director Dr Mike Ryan warned against trying to predict when the virus would disappear.
He added that even if a vaccine is found, controlling the virus will require a “massive effort”.
Almost 300,000 people worldwide are reported to have died with coronavirus, and more than 4.3m cases recorded.
The UN meanwhile warned the pandemic was causing widespread distress and mental ill health – particularly in countries where there’s a lack of investment in mental healthcare.
The UN urged governments to make mental health considerations part of their overall response.