The Government has approved the mixing of Covid vaccines in limited circumstances.
It comes as NIAC is due to advise on a potential vaccine booster campaign to start in September.
It said vaccine doses can be mixed in very limited circumstances - meaning a first dose of AstraZeneca could be followed by a second of Pfizer or Moderna.
It will only be in cases where someone had a reaction to dose one or has serious concerns about taking a second shot of the same vaccine.