Oxford University is set to begin a trial combining COVID-19 vaccines from AstraZeneca PLC and Pfizer Inc. that could enable greater flexibility in the use of scarce supplies globally.

The university will begin recruiting 820 participants over 50 years of age across eight U.K. sites this week, according to a statement Thursday. The AstraZeneca and Pfizer vaccines will be given in different orders and with two dosing intervals, four and 12 weeks apart.

The trial will allow researchers to see whether two shots of different vaccines produce better or worse results than two doses of the same product. The study could be key to relieving pressure on individual vaccine-makers to deliver shots if they run into manufacturing difficulties.