Up to 1,000 people a day can be vaccinated at the centres in Cavan and Monaghan.
Both began full operation this week with people in the 65 to 69 age groups receiving their first vaccines.
The vaccine portal today opened to people in the 60 to 64 age groups.
People have been warned the centres, which are based at the Hotel Kilmore in Cavan and Hillgrove Hotel in Monaghan, are only open to people who have booked an appointment.
AstraZeneca vaccines are the only vaccines being used in the centres at the moment and Cara O'Neill from the HSE says people won't have a choice in the dose they receive.
Speaking at the vaccine centre in Cavan she said things have been going well so far: