Viruses mutate, and vaccines can be tweaked. However, news that the Oxford-AstraZeneca vaccine may be less effective against the B.1.351 variant first discovered in South Africa, has raised the prospect of “booster” shots for people who have already been vaccinated against COVID-19, in addition to the second ‘booster’ already recommended. Already, an updated version of the Oxford-AstraZeneca vaccine is being developed. This involves tweaking the piece of genetic code for the coronavirus spike protein that it contains, to match the spike protein from the new coronavirus variant. Messenger RNA (mRNA) vaccines, such as those being produced by Pfizer and Moderna could be similarly tweaked, and these updated vaccines could either be given in place of, or on top of, the existing vaccines to create a more specific – and hopefully more effective – immune response.