Onwards and upwards

VACCINES are medical science’s nuclear weapons. Clean water and sewage disposal aside, they have saved more lives than any other public-health measure. Vaccines have wiped smallpox, a disease once dreaded by rich and poor alike, from the face of the Earth. They may soon do the same to polio. They have driven words like diphtheria and whooping cough from public discourse in rich countries, and might do the same for measles, mumps and rubella were it not for the vanity, selfishness or foolishness of a minority who will not immunise their children against these threats. They also offer the elderly protection, albeit imperfectly, against the lethal ravages of influenza.

But they could do more. Most vaccines are made in ways which would be familiar to Louis Pasteur, the 19th-century French polymath who put vaccination on a scientific footing. Pasteur’s method is either to weaken a pathogen in a laboratory or to kill it outright. The result, when injected or swallowed, acts as an antigen and stimulates an immune response—but it does not cause illness. Thus safely primed, the immune system reacts faster if and when it encounters the real thing.