(Bloomberg) -- U.K. Prime Minister Boris Johnson tightened pandemic rules to curb the spread of the omicron variant, advising people to work from home and mandating the use of so-called vaccine passports in large venues.

“It’s become increasingly clear that omicron is growing much faster than the previous delta variant,” Johnson said at a televised press conference on Wednesday, announcing the measures for England. It’s the “proportionate and responsible thing to do to move to Plan B,” he said.

Johnson Apologizes Over Christmas Party as Covid Rules Loom (3)

The activation of the so-called Plan B restrictions follows warnings that the new Covid-19 strain will overwhelm hospitals, given the U.K. has recorded a high daily caseload for months even before omicron emerged. Scotland, Wales and Northern Ireland already had tighter restrictions in place before Johnson’s announcement.

While the new rules fall far short of the lockdowns imposed previously, they still represent a significant change in approach and are politically risky for Johnson. The government had hoped an accelerated program of vaccine booster shots would mean no new restrictions would be needed over the Christmas period, after festivities were banned for many households last year.

The timing is also sensitive as Johnson’s government struggles to handle the backlash over allegations his officials held a rule-breaking party in his Downing Street office last Christmas, which has provoked a public outcry. 

Johnson’s press secretary on Wednesday denied he attended the event last December, but the prime minister apologized in the House of Commons on Wednesday after a video emerged showing key aides joking about a party. One of them, Allegra Stratton, later offered her resignation in a tearful statement.

The saga has angered even MPs in Johnson’s Conservative Party, one of whom accused him of using tougher Covid rules as a “diversionary tactic.”

Johnson had previously said he would wait to see evidence of Omicron’s impact on hospitalizations and deaths before reviewing Britain’s pandemic rules. Wednesday’s announcement comes as the U.K. recorded 131 new confirmed cases of the omicron variant, bringing the total to 568. 

Neil Ferguson, a government scientific advisor whose modeling led to the first pandemic lockdown, said Wednesday that the incidence of the omicron strain is doubling every two to three days in Britain, meaning it will likely become the dominant variant before Christmas.

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