German authorities on Thursday issued a COVID-19 exposure warning for more than 800 people who attended a dance party on Christmas evening in the northern state of Schleswig-Holstein.

One person who attended the party in the “Joy” discotheque in Henstedt-Ulzburg has tested positive for the omicron variant of coronavirus, the local health department said in a statement.

All attendees of the party, including those who are vaccinated or recovered from COVID-19, are now required to self-isolate for 14 days, Segeberg’s Health Department said.

Joey Claussen, the business manager of the discotheque, told local media that they obeyed all the rules, and only vaccinated and recovered people who presented a negative test were allowed to enter the venue.

The incident comes amid a nationwide debate on coronavirus restrictions in the country, with some experts calling for tougher measures, including blanket closures of bars, clubs, and indoor leisure settings, and strict limits on the number of attendees at public events.

Until recently, many states allowed bars and nightclubs to operate under the “2G plus” rule, requiring customers to present proof of vaccination or recovery from COVID-19, plus a negative test to enter the venues.

But critics say such measures are not sufficient to prevent the spread of the omicron variant, as studies show that vaccinated individuals can still get infected and transmit the virus to others.

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