Predicting viral evolution may let vaccines be prepared in advance

GENERALLY, IMMUNE systems mount responses only against pathogens that have already infected the bodies they are protecting. Science, though, can shorten the path to immunity by vaccination. This involves presenting the immune system with harmless or lookalike versions of dangerous pathogens so that it may create antibodies and killer cells hostile to the real thing in advance of any actual infection, thereby reducing its danger.

Like immune responses themselves, however, vaccination generally has to wait for the appearance of the pathogen in question before it can do its stuff. There is therefore a delay between a pathogen’s arrival on the scene and the deployment of a vaccine against it. That delay costs lives. Even in the case of covid-19, which has prompted the fastest vaccine-development programme the world has ever witnessed, millions are reckoned to have died by the time vaccinations began to be given in the rich world at the end of 2020.