WHEN the first trial results for covid-19 vaccines were announced back in November, it seemed that the end of the coronavirus pandemic was in sight. But then came news of first one dangerous new virus variant and then another. So where does that leave us? Will new variants scupper efforts to get life back to normal?

No one can say for sure what will happen next, of course. But many researchers are optimistic that in countries that get hold of enough vaccine, life could mostly return to normal in around …