It follows a big bump in cases linked to an Argyle House event, a medical ball at NEX on Friday night, and another high risk exposure at Finnegan's Hotel.

Anyone who attended The Cambridge Hotel in Newcastle between 6.30pm on Friday, December 10, until 2.30am on December 11 is a close contact and must immediately get tested and isolate for seven days.

All household contacts of close contacts should also be tested and self-isolate until a negative result is received by everyone in the household.

NSW Health said The Cambridge was visited by confirmed cases of COVID-19, and it was likely some of these cases have the Omicron variant of concern.

NSW Health is urgently contacting anyone who attended The Cambridge Hotel at these times and checked in via the QR code and is directing them and members of their households to immediately get tested and follow public health advice.

"NSW Health is reminding everyone of the importance of maintaining COVID-safe practices with transmission occurring at social events during the festive period," a statement said.

"Everyone should remain vigilant when celebrating with family, friends and colleagues and should not attend any social functions if they have any symptoms."