The Health Service Executive has told GPs that first dose allocations for patients in the 75 to 79 year age group will be limited next week.
GP practices were told the news through a new information bulletin.
The HSE said the decision to limit "dose one allocation" for the 75 to 79 age group was made "in order to maintain the equitable nature of the vaccination programme".
It wants to ensure that as many people as possible in the older age groups are vaccinated first.
The bulletin states: "The two key priorities for the distribution of available vaccine supplies next week (commencing 15 March) are:
a) to complete first dose vaccines for those patients in the 80 to 84 category and
b) administer second doses for those patients aged over 85 who are due them."
The HSE said the new limitations will impact on 100 of the 500 GP practices expecting vaccine deliveries next week.
So far, over 1,300 GP practices representing over 3,000 individual doctors have received and administered over 100,000 vaccine doses to older citizens.
Next week the HSE will deliver another 33,500 first dose vaccines to 500 GP practices to be administered to people in the community aged between 80 to 84.
It will also deliver second dose vaccines for those aged 85 and older.
The HSE is also changing its process for confirming the number of vaccines to be delivered to each GP.
Its new system means that GPs will no longer have to complete vaccine order forms and submit them online.
Instead, the amount of vaccines to be delivered will be automatically calculated on the number of patients registered to each GP practice on the Primary Care Re-Imbursement Service (PCRS).
Upward adjustments - to cater for private patients - will be managed on an individual basis by Vaccine Relationship Managers assigned to each GP practice in the past week.
The HSE bulletin also warned that "recent deliveries from Moderna have been less than the forecast quantity. Our ability to provide Moderna vaccine to GP practices has obviously been impacted by this.
"For the short-term we are only in a position to supply dose twos to the already committed dose ones."