The real nightmare scenario for anti-vaccine activists is the outbreak of a single drug-resistant strain. For instance, it would be dreadful if bird flu were to emerge, possibly through the massive migration of birds from China to Europe. The World Health Organisation has been talking about this for some time, but there is no evidence of bird flu emerging, although scientists are watching.

The risks are low and long term, which should reassure Britons. And with no serious incidents in recent months, it should make it more acceptable for officials to start to seek to persuade the public to accept some preventive measures. If it is an isolated outbreak of coronavirus, some experts may decide it is sufficient to vaccinate against it.