Europe is in a race against the clock to step up its vaccination and booster programmes amid concerns over the Omicron variant hitting its shores, European Union Commission President Ursula von der Leyen said during a news briefing Wednesday.

Von der Leyen said the bloc is facing a “severe double challenge.”

“On one hand, we are amidst the fourth wave,” von der Leyen said. And on the other hand, “we are now facing a new threat, that is the new variant Omicron,” she added.

“At this point we do not know all about this variant. But we know enough to be concerned,” she said, adding that “we know from our experience with the Delta variant, that it is a race against time.”

Von der Leyen urged members states to “do everything possible to make the best out of the time we have until we have certainty about the characteristics of transmissibility and severity of Omicron.”

“What is the bottom line? Hope for the best, prepare for the worst,” she added.

We are now facing a double challenge in the fight against #COVID19.

The rapid resurgence of Delta across Europe and a new variant of concern: Omicron.

Full vaccination and boosters provide the strongest protection there is. And they are available now. https://t.co/FOuda4Jbvj

— Ursula von der Leyen (@vonderleyen) December 1, 2021

The EU Commission put forward a coordinated EU approach on Wednesday to address the challenges from the resurgence of Covid-19 in many member states this fall.

Among the measures suggested, member states “should continue to implement a joint strategy to limit the entry of the Omicron variant into the EU, with regular, daily reviews of essential travel restrictions,” the Commission said in a statement.