Considerable international interest was generated at the beginning of June when Martina Sester, Professor of Immunology at Saarland University, published a preprint of her research into mixing different types of COVID-19 vaccines. After a rigorous peer review process, the results of the study have now been published in the journal Nature Medicine. The results have also been picked up by Germany’s Standing Committee on Vaccination (STIKO), which is now recommending a combination vaccination for adults including those over the age of sixty. The research team led by Martina Sester found that people who receive the 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.