This is due to potential issues with the AstraZeneca vaccine among older people.
HSE Chief Clinical Officer Colm Henry has said that the "preferred option" will be for older people to be given the Pfizer and Moderna vaccines, also known as the mRNA vaccines.
This is opposed to the AstraZeneca vaccine, of which Ireland has ordered over a million doses.
Recent reports have claimed that the AstraZeneca vaccine is potentially less effective when administered to older people.
Speaking on Wednesday morning, Henry said: "We've seen the advice come through from the EMA (European Medicines Agency) that based on the current evidence we have, and bear in mind we are dealing with evolving evidence all the time, the advice generally is to give the mRNA vaccines, to preferentially give them to older people."
He did stress however that this could change as more information comes to light, but that "at this point in time, it is preferred" for older people to get the mRNA vaccines.
35,000 doses of the AstraZeneca Covid-19 vaccine will be delivered to Ireland next week and three instalments of the vaccine are due to be delivered in quarter one of 2021.
It is now believed that the AstraZeneca vaccine will be reserved for younger people, among whom it is understood to be more effective.
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Henry also said that of 580 nursing homes, 117 are incomplete in terms of vaccination.
