The Covid-19 vaccine portal has opened for 49 year olds to register.
High risk patients and frontline healthcare workers who have yet to receive an appointment can also register.
People will be given Pfizer or Moderna when vaccinations start later this month.
However it's expected Johnson and Johnson and AstraZeneca will be offered if they aren't available.
Consultant in Infectious Diseases at St James' Hospital in Dublin, Professor Cliona Ni Cheallaigh, says the choice is a good thing.
"It allows people to make up their own minds as to whether they feel that the very small risks of blood clots with Astra Zeneca or Johnson and Johnson outweigh the risks of perhaps waiting longer to get Pfizer or Moderna."
