Matthew Snape's study on mixing COVID-19 vaccines expanded


St Cross Member of Common Room Professor Matthew Snape, Associate Professor in Paediatrics and Vaccinology at the University of Oxford, is the Chief Investigator of the first trial to explore alternating different COVID-19 vaccines.

The first phase of the trial has involved evaluating four different combinations of prime (initial) and booster (follow-up) vaccinations: Oxford-AstraZeneca prime and booster, Pfizer prime and booster, or Oxford-AstraZeneca prime with a Pfizer booster, and vice versa. It is now being expanded to include doses of Moderna and Novavax.

Combining vaccine doses could give broader immunity against the virus and its variants, and could allow countries to be more flexible in rolling out the vaccine.

The additional study will seek to recruit adults aged over 50 who have received their first dose in the past eight to 12 weeks. More than 800 volunteers have already taken part in the study, and six new "arms" of the trial will recruit a further 1050 volunteers in total to the programme. The results of the first phase of the trial are expected in May. 

Professor Snape said the option to mix vaccines "will give us lots of flexibility, not just in the UK, not just in Europe - where we're looking at restricting use of some vaccines for some age groups - but across the world, where we have, perhaps, a little bit more intermittent supply of vaccines. Let's hope that we can actually use this to get two doses of vaccine to as many people as possible."

If you are interested in volunteering, you can find out more about the study at