A UK Covid trial has been launched to see if giving people different Covid vaccines for their first and second doses works as well as the current approach of using the same type of vaccine twice.
The idea is to provide more flexibility with vaccine rollout and help deal with any potential disruption to supplies.
Scientists say mixing jabs could also possibly give even better protection.
The vaccines minister said no changes would be made to the UK’s current approach until at least the summer.
Currently, official guidance from the Joint Committee on Vaccination and Immunisation (JCVI) says anyone already given the Pfizer-BioNTech or Oxford-AstraZeneca jab as part of the UK’s approved immunisation programme should get the same vaccine for both doses.