The death toll already exceeds 1.5 million in the 53 countries of what the WHO terms as its Europe region.
The WHO warned of “high or extreme stress” in intensive care units in 49 of the nations by March 2022.
Europe is facing a surge in cases, prompting Austria to return to lockdown and others to consider fresh measures.
A number of countries – including France, Germany and Greece – could also soon make booster jabs a requirement for their citizens to be considered fully vaccinated.
But several countries have seen fierce protests against new measures. The Netherlands saw several nights of rioting over a partial lockdown.
In its assessment, the WHO warned Covid was the top cause of death in its Europe region.
“Cumulative reported deaths are projected to reach over 2.2 million by spring next year, based on current trends,” the WHO said on Tuesday.
Confirmed Covid-related deaths recently doubled to almost 4,200 a day, it added.
A high number of unvaccinated people and the prevalence of the Delta variant in some countries were key factors behind high transmission rates in the Europe region, the WHO said.
The WHO Europe director, Dr Hans Kluge, urged those who were still unvaccinated to get the jab.
As well as European nations, the WHO also considers Israel and ex-Soviet states like Tajikistan and Uzbekistan as making up the region.