Covid-19 variant spread across the globe on Sunday, shutting borders and renewing curbs as the EU chief said governments faced a "race against time" to understand the strain.
Dubbed Omicron, the strain, first discovered in southern Africa, represents a fresh challenge to global efforts to battle the pandemic, amid fears it is highly infectious.
Several countries have already re-imposed measures many had hoped were a thing of the past. "We know we are now in a race against time," said European Commission chief Ursula von der Leyen.
Vaccine manufacturers needed two to three weeks "to get a full picture of the quality of the mutations", she added. A long list of countries have already imposed travel restrictions on southern Africa,