He added that the planned easing of restrictions in June remains "low to medium risk".
Chief Medical Officer (CMO) Dr Tony Holohan has warned that unvaccinated people should "limit" their interactions as Ireland continues reopening.
In his latest letter to the government, sent on 26 May but only published this week, Holohan said that vaccination was proceeding at or ahead of schedule, with high uptake, but added that there are concerns for those who have yet to access a vaccine.
Holohan also pointed to early evidence of high levels of vaccine effectiveness and added that it was the view of the National Public Health Emergency Team (NPHET) that the easing of restrictions for June remains "low to medium risk".
The letter added that in spite of "progressive relaxation of measures", "caution should continue to be exercised by those that are not fully vaccinated", saying that people who have yet to receive the jab "should seek to limit their indoor interactions with people who are also unvaccinated and avoid crowded indoor situations".
Holohan also said that the incidence of Covid-19 is at or below what model scenarios projected in late April, as daily case numbers are relatively stable at 400 to 500 a day. The number of patients in hospital and ICU has also decreased.
The letter added that there is also uncertainty about the impact of the "Delta" variant, which originated in India, as 89 cases had been identified in Ireland up to last week.
The letter was sent to the Government on 26 May and NPHET will provide a briefing to the media today (2 June).
It comes as, over the weekend, Dr Holohan said he was "absolutely shocked" after what he described as a "major open air party" in Dublin City Centre.
Dr Holohan said he saw "enormous crowds" while driving past the centre to collect someone from work at approximately 8.15 pm on Saturday evening.
The CMO added that the scenes are "what we do not need when we have made so much progress".
Taking to Twitter on Saturday night the CMO wrote: "Drove into Dublin City Centre to collect someone from work at 815 PM. Absolutely shocked at scenes in South Great George’s St, Exchequer St, South William St area.
"Enormous crowds- like a major open air party. This is what we do not need when we have made so much progress."
