Governments have grossly over-reacted to the pandemic, people have begun to declare. The smattering of initial voices pressing for an end to lockdowns has given way to a clamour. So governments are caving in and easing restrictions on movement and economic activity. But this only sends the Covid-19 infection rate higher – and one by one, countries are hit with a second wave of infections.

Christian Drosten, the director of the Institute of Virology at the Charité hospital in Berlin – and one of those who identified the Sars virus in 2003 – calls this the “prevention paradox”...