The U.K. health secretary said at least 10 people were in hospital with the variant, which experts believe may cause a milder form of Covid-19 but can evade immunity and spread rapidly.
Some of the world’s biggest producers of Covid-19 vaccines are divided over whether the shots protect against omicron, while new, variant-specific vaccines are already being developed.
Italy, which has one of the highest vaccination rates in the world, will require proof of vaccination or recovery to enter many public spaces and a negative test to use public transport.
Early data suggests the variant can also get around some of the immunity from vaccines, though they still appear to protect against serious illness and death.