For the record: The World Health Organization tweeted that it’s in “close contact” with British officials on the variant, as the Dutch government introduced a ban on passenger flights from the United Kingdom, effective Sunday morning through Jan. 1, after finding a case with the same strain in the Netherlands.

Driving the news: British Prime Minister Boris Johnson said Saturday although there’s “considerable uncertainty,” the new strain “may be up to 70% more transmissible” than the original version of the disease. England’s chief medical officer Chris Whitty said the strain accounted for over 60% of new cases in London over the past week.

Johnson said during the news conference that an expected Christmas Day reprieve — a planned postponement of restrictions that would permit up to three households to convene in “Christmas bubbles” — would be canceled for Tier 4 zones.