Could combining Pfizer's and AZ's COVID-19 vaccines fill supply gaps? U.K. researchers aim to find out

Given that the COVID-19 vaccines from Pfizer and AstraZeneca each require one dose, followed a few weeks later by a booster shot, could the two products be used interchangeably?

That’s the question researchers from the Oxford Vaccine Group have set out to answer with a new clinical trial designed to address a mounting problem: The demand for COVID vaccination in many locales around the world is far outstripping the supply.