The National Immunisation Advisory Committee has advised vaccines can be mixed.
NIAC has told Health Minister Stephen Donnelly it can be done in limited circumstances.
This could be where someone has had an adverse reaction to dose one, or has serious concerns about taking a second dose of the same vaccine.
It would allow a first dose of AstraZeneca to be followed by a second dose of Pfizer for example.
The HSE and the Department of Health is now working to operationalise the advice.
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 jabs would be given towards the end of September.
*Reporting by Sean Defoe