There is a story of two men travelling on a train through Africa. One of them is throwing powder out of the window. His puzzled travelling companion asks him what he is doing. He replies that he is throwing powder out of the window to keep the elephants away. “There are no elephants,” replies the inquisitor. “There you are,” retorts the powder-thrower, “it works!”

The problem with prevention is that things, once prevented, become invisible. Somehow, public health must make visible and real threats to public health that have gone (such as childhood infections) and maintain vigilance and awareness and a commitment to perpetuate preventive programmes such as childhood immunisation and vaccination that will keep the elephants away.