we know that the vaccines won’t work for everyone, which may dent the effectiveness of roll-out programmes. How can we find out whether we are still at risk after having had a jab?

Promise on this front comes in the form of commercial tests that offer to measure precise levels of antibodies in the blood after infection or vaccination. Theoretically, it should be possible to keep an eye on these over time to see when levels are waning. Unfortunately, it seems doubtful whether the tests currently live up to the hope.

Many of the answers to these quandaries lie in determining how much the virus can spread even among those who have been inoculated. Until then, vaccination won’t be the jab-and-go solution many of us will have hoped for. ■