Dr Tony Holohan has issued a specific plea to young people in the run-up to Christmas - as he revealed one in six have still not come forward for a vaccination or a booster shot.
Christmas 2021 will once again look very different as pubs shut up shop at 8pm and work parties are cancelled en masse.
Speaking as the case numbers were announced by the HSE, Dr Holohan said: "As we continue to see incidence rising in our young adult population, I would urge all parents, guardians and extended friends and family to support the young people in your lives to reduce their contacts.
"I know that this is not an easy task for any of us and it can feel very unfair that we continue to ask so much of our young people, particularly at this special time of year.
"This group have made significant sacrifices in order to protect loved ones and I would like to thank them for that. It is important now that we continue to encourage and support each other to make sacrifices, take responsible actions and continue to follow the public health advice."
He told the younger generation to do one thing in the buildup to Christmas, saying: "This week, try and only meet with the people with whom you will spend Christmas Day. Keep your contacts as low as possible in order to protect those around you."
The CMO also issued a reminder of what he believes to be the most important advice anyone could give out.
He noted: "As we roll out the booster programme, it is important to remember that approximately one in six young adults are yet to come forward for vaccination or are not fully vaccinated. Vaccination offers very good protection against severe illness, so it is important that everyone who is eligible for a vaccine comes forward for one.
"If you display any symptoms of COVID-19 then you must self-isolate straight away and arrange a test. This is the single most important piece of basic public health advice. Do not meet up with others and put them at risk of COVID-19 or another respiratory infection. Do not rely on a negative antigen test as a basis for not isolating.
"Omicron now accounts for about two thirds of confirmed cases of COVID-19 in Ireland. Public health teams are reporting a higher level of infection among household close contacts as a result of Omicron infection.
"If there is one positive test, whether from a PCR or an antigen test, within a group such as a household then there is a significant chance that others are already infected, even if not yet testing positive. If one person from a household tests positive prior to an event or gathering, then none should attend."
