There are still big unanswered questions about the first variant of the coronavirus which was announced by the government last week.
It is different to the South Africa-linked variant which Health Secretary Matt Hancock referred to in today's news conference, when he said two cases had been discovered in the UK.
Given the first variant's explosive spread in the east and southeast of England, the most immediate question is whether the Tier 4 "stay at home" restrictions will be enough to bring it back under control.
Professor Neil Ferguson, the epidemiologist who closely tracks the coronavirus epidemic, said the next two weeks should lead to a flattening of the curve to some degree because the enhanced restrictions over Christmas will reduce social mixing.
But children are the unknown factor. There has been a rise in the proportion of cases in those under 15 and if ongoing research shows children are more infectious, then schools may not be able to re-open in January with face-to-face teaching.
The Christmas travel restrictions will also slow the movement of the virus around the country.
But Prof Ferguson said the first variant is now "everywhere" and the Tier 4 controls are likely to affect more areas in January. That may buy time until more vulnerable people have been vaccinated.
That's the other big question: are the vaccines likely to be effective against the variant?
Almost certainly, seems to be the scientific consensus. The vaccines stimulate the immune system to make multiple types of antibodies against the virus - and even if one becomes redundant because of a new mutation the others should still work.
More of a concern are experimental antibody treatments. These are based on one or two of the antibodies raised against the virus, so there is a greater chance of them being knocked out.
Scientists are working on the belief that the variant announced last week arose in a single person in southeast England who had an immune system that was unable to completely block the virus, allowing it to mutate and escape.
It has since spread far and wide, with Prof Ferguson saying it's likely that the virus is now in "most, if not all" European countries.
That rather undermines the rationale behind the restrictions on travel from UK. The seeds for a new wave of infections have already been sown.
The rapid emergence of the first variant shows how the rollout of the jab is not game over for the virus.
Tracking the mutations and perhaps reformulating the vaccine could be the story of 2021.