The National Immunisation Advisory Committee has advised vaccines can be mixed in some circumstances.
Health Minister Stephen Donnelly has signed off on the move and confirmed a campaign of booster vaccines is now being worked on.
There will be limited mixing of vaccines for now, however.
Where someone has had an adverse reaction to dose one or has serious concerns about taking a second dose of the same vaccine, they may be given another.
For example, a first dose of AstraZeneca may be followed by a second dose of Pfizer in some instances.
The HSE and the Department of Health is now working to operationalise the advice.
It comes as Ireland is set to move away from the use of the AstraZeneca and Johnson & Johnson vaccines.
Meanwhile, NIAC is expected to make a recommendation on a potential campaign of booster vaccines next week.
No decision has been taken, but if it was given the go-ahead it's likely the first booster jabs would be given towards the end of September or early October.
The World Health Organisation has asked richer countries not to proceed with boosters until at least the end of September, in a bid to help the developing world get vaccinated.