BACK in 1796, an English country doctor named Edward Jenner carried out the experiment that was to make him famous. He took pus from a cowpox pustule on the hand of a milkmaid and transferred it to an open cut on the arm of 8-year-old James Phipps. Later, he injected the boy with smallpox virus, and though the youngster became ill he recovered with no lasting effects.
Jenner’s experiment, the first vaccination, was the start of a process that has progressively isolated humans from micro-organisms. Vaccination was followed by urbanisation and sanitisation. Over the intervening centuries, water and food have been purged of infectious agents, children…
