There are good reasons to be concerned about the Omicron variant. For starters, this strain has 50 mutations, twice as many as Delta. Early reports from South Africa, where the virus has been circulating for a while, suggest it’s outcompeting Delta and spreading rapidly. There is a concern, too, that it could blunt the vaccines, because more than half of the new mutations affect the spike protein that the jabs are designed against. But all of this is theoretical: we need real-world data. So we won’t know whether it really is more transmissible, or how the vaccines perform against it, until long after Christmas. The concern, for now, remains Delta, as Chris Whitty said last week. On that front, the news is better.