The head of the European office of the World Health Organization (WHO) urged people to get a booster jab, stating that it was the single most important defence against the more transmissible Omicron variant.
Dr Hans Kluge was holding a joint press conference with Austrian Health Minister Wolfgang Mueckstein.
Kluge warned that COVID-19 infections are already 40% higher now than during the same period last year. The Omicron variant has already been detected in at least 38 of the member states in the region.
Kluge said early evidence showed that the booster jab was essential in the fight against Omicron.
He said the variant was already dominant in the UK, Denmark and Portugal, with cases doubling every 1.5 to three days and that it would be dominant across the whole region "within weeks."
"The sheer volume of new COVID-19 infections could lead to more hospitalisations and widespread disruption to health systems and other critical services. It has unfortunately already resulted in hospitalisations and deaths," he stressed.
It comes a day after WHO chief Dr Tedros Adhanom Ghebreyesus urged people to skip holiday gatherings, warning that "an event cancelled is better than a life cancelled."
More than 2.6 million COVID-19 infections were reported across the 51 counties included in the WHO European region in the weeks ending on December 13 — the highest of any region for the 12th consecutive weeks, according to the UN's agency COVID-19 dashboard.
Over 26,000 people lost their lives, taking the region's death total death toll to more than 1.6 million.
Dr Kluge warned in a statement last week that as Europe goes into the holiday season, it will be dealing "with two highly transmissible variants, with the potential to overwhelm our already overstretched systems."
"The European region was the epicentre of the pandemic even before the emergence of Omicron, with surging cases of the Delta variant," he explained then.
According to the European Centre for Disease Prevention and Control (ECDC), the latest variant of concern has now been detected in 64 countries worldwide including most European Union member states.
As of December 16, the UK had detected Europe's highest number of Omicron infections with 4,773 cases. It was followed by Denmark (267), Germany (237), Norway (179), and the Netherlands (149).
Evidence gathered so far suggests community transmission of Omicron doubles every 1.5 to three days, the WHO said on Monday. It also appears to be more resistant to vaccines with people that have been fully vaccinated or who have recovered from the disease more likely to be infected or reinfected by Omicron.
The UN agency also highlighted that it is too early to conclude that Omicron is a milder variant than Delta.
In his statement last week, Dr Kluge urged people to "exercise caution" over the festive period by attending only small social gatherings, avoiding crowds, wearing masks, observing physical distance of at least one metre and testing regularly.
He also called for people to "get vaccinated as soon as possible."
"Vaccines remain the best way to prevent severe disease and death, even with the arrival of Omicron," he said.