Sixty-four people tested positive for the Omicron variant after a Christmas lunch attended by 150 people in Denmark. It means that more than a third of attendees came away with the recently-discovered variant after the event on November 27. More than a thousand more “close contacts” or “close contact to close contacts” were also potentially exposed, Andreas Peder Schultz, a spokesperson for the Danish Patient Safety Authority, said on Monday. Omicron vs Delta: battle of coronavirus mutants is critical The event was at a community centre in the Viborg region of Denmark, according to the Viborg Flokeblad local newspaper. Students from two local schools took part, it said. It was also not immediately clear how severe their symptoms were, or how many of the attendees were vaccinated. Vaccine policy in Denmark allows children aged 12 and up to receive shots, and some 77 per cent of Danes were fully vaccinated as of December 1, per Our World in Data. As of Monday, Denmark had recorded 261 Omicron cases. Tests there are revealing a surge of Omicron cases, leading officials to believe that it is spreading locally rather than only among travellers exposed abroad. Omicron was first named as a variant of concern by the World Health Organization on November 26. It is too early to tell if is more transmissible, can escape vaccines more readily, or can cause more or less severe symptoms. Vaccines remained the most effective protection against severe disease, hospitalisation, and death after infection in the face of the Delta variant. The news of the Omicron outbreak comes as the country is seeing a rapid increase of cases since mid-September, from a seven-day average of 328 new daily cases on September 22 (about 56 per million) to 4583 cases (about 788 per million) reported on December 4, per Our World in Data. This is the latest in a series of reports of Omicron clusters since late November. Norway party is biggest Omicron superspreader outside South Africa Up to 120 vaccinated people in Norway were reported to have caught Covid-19 after a Christmas party on November 26, 13 of which were confirmed to have Omicron, per the Norwegian newspaper Dagbladet . At least five of 12 vaccinated people who caught mild cases of Covid-19 at a wedding on November 27 in Alameda County, California, were also found to carry Omicron. A fully vaccinated Minnesota man also caught a mild case of Omicron and started displaying symptoms on November 22. He later said 15 of his friends came back infected with Covid-19 after an anime convention in New York City that they all attended together. It is not clear if his friends had Omicron. Read Business Insider’s story .