More than 400 million doses of coronavirus vaccines have been administered across the continent in the last six months.
But the WHO's regional office has repeated calls for vigilance and continued health restrictions amid concern over new variants of the virus.
"Although we’ve come far, we haven’t come far enough," WHO Regional Director for Europe Hans Kluge told a press conference.
"Vaccination coverage is far from sufficient to protect the Region from a resurgence," he added.
So far, around 30% of European adults have received at least one dose of a COVID-19 vaccine, and 17% have been fully vaccinated.
But Kluge warned that vaccination needs to happen "at a much faster rate" this summer to reach the "considerable" target of when at least 80% of the population are inoculated.
"We should also remember that being vaccinated does not automatically stop us from becoming ill or spreading the virus," said Kluge.
"Vaccination does, however, reduce the chance of becoming seriously sick or dying from COVID-19."
The WHO has also recommended that citizens avoid "closed, confined, or crowded" spaces that put citizens at a higher risk of being infected.