European Commission President Ursula von der Leyen said that the Omicron is expected to be the dominant coronavirus variant in the bloc by mid-January.
But von der Leyen said she is confident the EU has the “strength” and “means” to overcome the disease, with over 66% of the EU's population now fully vaccinated.
“Like many of you, I’m sad that once again this Christmas will be overshadowed by the pandemic,” she said.
The new variant was first identified by South African researchers and was designated a "variant of concern" in late November. It appears to spread much more quickly than previous COVID-19 variants.
The European Centre for Disease Prevention and Control warned that vaccination alone will not prevent Omicron from spreading.
Dr Andrea Ammon, director of the EU public health agency, said that "a further, rapid increase in Omicron cases is imminent" in the European Union and the European Economic Area.
"We assess the probability of further spread of the Omicron variant in the EU/EEA as very high and it is considered very likely to cause additional hospitalisations and fatalities," Ammon said in a video statement.
She called for countries to take urgent "strong action" to reduce transmission and alleviate the burden on health care systems.
The comments echoed those of the World Health Organization, which warned Omicron is “spreading at a rate we have not seen with any previous variant”, as it called on the world to use all tools available to fight the coronavirus pandemic.
“I need to be very clear: vaccines alone will not get any country out of this crisis," said WHO Director-General Tedros Adhanom Ghebreyesus said.
"It’s not vaccines instead of masks, distancing, ventilation, or hand hygiene. Do it all. Do it consistently. Do it well,” he told a media briefing on Tuesday.
He once again highlighted vaccine inequity, with many Western countries racing to roll out vaccine booster jab campaigns while many poorer nations have still not administered first jabs.
"Let me be very clear: WHO is not against booster doses. We are against vaccine inequity," said Dr Tedros.
"It's a question of prioritisation. Giving booster doses to groups at low risk of severe disease or death simply puts at risk the lives of those at high risk who are still waiting for their first doses," he insisted.
He pointed out that 41 countries have still not managed to vaccinate 10 per cent of their population and 98 countries have not reached the 40 per cent mark. "If we end the inequity, we end the pandemic. If we allow inequity to continue, we allow the pandemic to go forward," he insisted.
Omicron ‘could overwhelm’ health systems
Countries across Europe and the rest of the world have been enacting further restrictions to fight the spread of COVID-19, and especially the new variant Omicron.
"Seventy-seven countries have now reported cases of Omicron, but the reality is that Omicron is probably in most countries even though it has not yet been detected," Ghebreyesus said.
He added that the WHO was concerned that some considered Omicron to be more benign than other strains.
“Even if Omicron causes less severe symptoms, the number of cases could once again overwhelm unprepared health systems," he said.
According to Abdi Mahamud, incident manager at WHO, the spread of the variant is such that it could become a majority in some European countries by mid-December when they are still dealing with the impact of the fifth wave of infection caused by the Delta variant.