The Oxford/AstraZeneca vaccine induced a stronger cellular immune response in elderly adults than the BioNTech/Pfizer shot, potentially providing more protection against severe Covid-19 and new virus variants.

In the first head-to-head comparison of the two vaccines, scientists discovered that both shots elicited an antibody response in the group of over-80s, tested five to six weeks after the first shot. However, participants who received the AstraZeneca jab were more likely to also have a T-cell response. 

Vaccines teach the immune system — which includes both antibodies and T-cells — to recognise part of the Sars-Cov-2 virus. The antibody response of different vaccines has already been studied, but so far less data has been gathered on the T-cell response because it is harder to measure.