People who receive the COVID-19 vaccine from AstraZeneca as their first dose and the BioNTech vaccine as their second shot show a significantly stronger immune response than those who receive the AstraZeneca vaccine on both occasions. This ‘mix-and-match’ approach also delivers a slightly higher bodily immune response than two shots of the BioNTech vaccine. These are the findings of a research team led by Martina Sester, Professor of Immunology at Saarland University. Sester’s team has spent several weeks examining in detail the immune response of 250 individuals. Their provisional but very promising results have yet to be published in a peer-reviewed journal.