Participants will be given one vaccine dose, followed by a second booster shot of a different vaccine.

The trial will combine the AstraZeneca Oxford University vaccine with the fires of biotech One.

Scientists will assess the participants immune response as well as monitor for any unexpected side effects.

About 800 volunteers over the age of 50 are being recruited to take part in the trial, with results expected in June.

AstraZeneca's shot is also being tested in combination with Russia's Sputnik V vaccine.

British researchers said the study was crucial for understanding whether vaccines could be rolled out with greater flexibility around the world, particularly as a steady supply of vaccines is always in question.

Matthew Snape and Oxford Vaccine Ologists, who is leading the trials that the results could inform vaccine deployment in the second half of the year.