Scientists expect that the Omicron variant will be able to spread much more quickly but it is not known whether it will cause more serious infections.
Switzerland has introduced a 10 day quarantine for UK travellers which is likely to ruin many British tourists’ ski holidays.
From December 1, Spain will only allow vaccinated British tourists to enter the country. The rules apply to every Briton over the age of 12.
Portugal will require every tourist, including vaccinated people, to provide a negative test result to enter. It will introduce the rule from December 1.