People ask me a lot what I think about "mix and match" approaches for COVID vaccines. We are all excitedly awaiting the ComCov Study, but I'm full of enthusiasm for 3 reasons: 1/4 https://twitter.com/OxfordVacGroup/status/1382268210125361152

Reason 1: Precedent. It's how we give licensed vaccines anyway. I usually run a Travel clinic, and we mix and match your Hep A, rabies etc vaccine. When we are giving you a booster, we don't mind which one you had in the past - evidence shows they can boost each other 2/4

Reason 2: Necessity. With scarcity & supply chain issues for COVID vaccines, much of the world may not have the luxury of matching the 2nd dose to the 1st, so an evidence base to support being able to boost one spike vaccine with another will be incredibly useful. 3/4

Finally for years, we @JennerInstitute and others believed heterologous prime-boost the best way to get optimal immune responses: repackaging the antigen in a novel way to get attention. @FletcherHelen reminded me today I wrote a review on it in 2003! 4/4 https://www.researchgate.net/publication/5890955_Prime-boost_strategies_for_malaria_vaccine_development