"Recent international experience and the rapid spread of the highly transmissible Omicron variant here means we can expect to see a large number of cases over the next short period of time.
"We all remember the call to ‘flatten the curve’ in the early days of the pandemic – we have successfully driven down incidence of disease in the community before - we can and must now work together to do it again.
He added: "By choosing to act safely right now, together we can limit the impact this disease will have in the weeks to come and in doing so, we can protect the vulnerable, prevent unnecessary deaths and ensure the continued operation of our healthcare system and other essential services."
Deputy Chief Medical Officer Dr Ronan Glynn also asked the public to limit their social contacts over the holiday season.
"The growth of the Omicron variant represents a significant threat to people’s ability to safely enjoy the Christmas and New Year period.
"Over the coming days please think about each of your social contacts and consider whether now is the time to be meeting with them.
“Meet up outside where possible and avoid all crowded settings.
"If you have symptoms please isolate immediately and arrange a PCR test – do not go to work and do not meet up with other people. If you are identified as a close contact it is vital that you restrict your movements."