The HSE's registration system for a Covid-19 vaccine resumes today.
44-year-olds can sign up online or by phone today, 43-year-olds tomorrow, then those a year younger over subsequent days.
The health service says it expects appointments will start to be scheduled from the middle of this month.
Meanwhile the chief medical officer says the country will remain at riskin June and July because a large amount of the population won't be vaccinated.
In a letter to the Health Minister, Dr Tony Holohan expressed concern about variants.
He says case numbers and the incidence rate remain relatively high.