European Union leaders have agreed that administering booster jabs is “urgent” and “crucial” to tackle the surge of coronavirus infections across the continent and the emergence of the new Omicron variant.

With the festive season looming, the bloc’s leaders also stressed the importance of coordinated action to avoid a confusing cacophony of rules in the 27 member states, and to ensure that Covid-19 certificates continue to guarantee unrestricted travel.

In their summit’s conclusions, leaders gathered in Brussels insisted on the need for a harmonised approach to avoid limitations to free movement between member countries or travel into the region being hampered.

But alarming rises in infections have already prompted many European governments to implement public health measures and new restrictions in recent weeks.

France will restrict arrivals from Britain because of fast-spreading Omicron cases, putting limits on reasons for travelling and requiring 48-hour isolation upon arrival. The new measures will take effect first thing on Saturday.

Italy this week required negative tests from vaccinated visitors, raising concerns that similar moves elsewhere will limit the ability of EU citizens to travel to see friends and relatives over the holidays.

Portugal adopted a similar measure on December 1, requiring a mandatory negative test for all passengers on arriving flights, regardless of their vaccination status, point of origin or nationality.

Greece announced on Wednesday that all arriving travellers must display a negative test, starting from Sunday, unless they have spent less than 48 hours abroad.

Greek Prime Minister Kyriakos Mitsotakis said additional restrictive measures, such as extra testing for visitors, should only apply during the Christmas period “in order for us to gain additional time to boost as many people as possible. It’s a battle against time.”

He said that booster doses were key to counter the spread of the new variant.

“The one answer to the Omicron right now is the acceleration of our vaccination programme, with a particular emphasis on the booster shots,” Mr Mitsotakis said. “In Greece, we are one of the first European countries to open booster shots to the entire population.”

Irish Prime Minister Micheal Martin said that leaders had significant concerns about Omicron’s capacity to spread rapidly and create pressure on health systems.

Omicron is expected to be the dominant coronavirus variant in the European Union’s 27 nations by mid-January, according to European Commission President Ursula von der Leyen. She said the bloc was well prepared to fight it, with more than 66% of the EU population now fully vaccinated.

However, while nations like Portugal and Spain have immunised the vast majority of their people, other countries lag way behind. Bulgaria, for example, has just 26.6% of its population fully vaccinated, according to the European Centre for Disease Prevention and Control.

Leaders also pledged to continue to export doses outside the bloc to achieve global vaccination. With more than one billion doses sent to the rest of the world, the EU is the largest exporter of Covid-19 vaccinations.