The Omicron coronavirus variant is likely to spread internationally, posing a very high global risk of infection surges that could have severe consequences some areas, the World Health Organization (WHO) said on Monday.

The UN agency urged its 194 member states to accelerate vaccination of high-priority groups and, in anticipation of increased case numbers, to “ensure mitigation plans are in place” to maintain essential health services.

“Omicron has an unprecedented number of spike mutations, some of which are concerning for their potential impact on the trajectory of the pandemic,” the WHO said. “The overall global risk related to the new variant … is assessed as very high.”

To date, no deaths linked to Omicron had been reported, though further research was needed to assess Omicron’s potential to escape protection against immunity induced by vaccines and previous infections, it said.

“Increasing cases, regardless of a change in severity, may pose overwhelming demands on healthcare systems and may lead to increased morbidity and mortality. The impact on vulnerable populations would be substantial, particularly in countries with low vaccination coverage,” it said.