So much for the turkey. Staff at US vaccine maker Moderna spent Thanksgiving studying the Omicron coronavirus variant. Moderna’s shares have since risen by a third, as have those of German peer BioNTech. That is a measure of the hopes pinned on mRNA pioneers in the face of the latest threat.

A big advantage of this technology is its adaptability. Unlike traditional vaccines, which involve growing cells in a vat, mRNA jabs are genetic code, wrapped in tiny bubbles of fat. If Omicron evades existing vaccines, new versions could be ready in as little as 100 days.

It is possible that the new variant will diminish, not demolish, the effectiveness of vaccines. If so, tweaks to their design may be superfluous. A third dose of the existing vaccines might be enough just to top up immunity. Omicron is no reason to panic but a great reason to get boosted, the boss of the National Institutes of Health said on Sunday.