It comes as yesterday NPHET asked over 70s to stay away from people outside "a very small core group" of family, carers and friends.
613 more people tested positive for the virus, a level of new infection not seen since mid-April.
Ten more patients have also been reported dead, though eight of those cases date back at least a month.
Close to 3,100 have tested positive for Covid-19 on the island of Ireland in the last three days.
Professor of Health Systems at DCU, Anthony Staines, says Dr Ronan Glynn's advice to older people is not going to do enough.
"That is a very large part of the whole population, I understand his advice and it is sound, but it is not a solution.
"What we are seeing happening is that case rates rose in younger age groups and have now started rising in older age groups."
He said there is a "leakage" of cases from younger age groups to older age groups.
To date, there has now been a total of 1,810 Covid-19 related deaths in the country.
Of the cases announced yesterday: 224 cases were in Dublin, 58 in Donegal, 46 in Cork, 44 in Kildare,31 in Limerick, 28 in Laois, 21 in Kerry, 19 in Galway, 17 in Clare, 13 in Meath, 12 in Louth and 12 in Monaghan.
There was also nine cases in Offaly, nine in Tipperary, nine in Wicklow, eight in Cavan, eight in Wexford, seven in Carlow, seven in Sligo, seven in Roscommon, six in Mayo, five in Kilkenny, five in Westmeath, with the remaining seven cases in three counties.
Acting chief medical officer Dr Ronan Glynn said yesterday:
"The numbers being reported today and over the past week represent a significant escalation in the profile of Covid-19 in Ireland.
"For those aged 70+ and those who are medically vulnerable to Covid-19, it is strongly recommended that you should limit the number of people you meet to a very small core group of family members, carers or friends, for short periods of time, while remaining physically distant."