The British government on Tuesday announced a Plan A and a Plan B for getting through the challenging autumn and winter months in the face of a stubborn pandemic driven by the highly contagious delta variant.

The hope is that Plan A will be enough. As part of it, the government will offer free booster shots to 30 million people to protect front-line health workers, those older than 50 and any other medically vulnerable people.

However, if the virus begins to spread exponentially and threatens to overwhelm hospitals during flu season, Plan B might be required. In that case, the government said, it was prepared to reinstate restrictive measures, including mandatory mask-wearing in crowded spaces and the use of vaccine passports to allow people to go to large events and nightclubs.

The news that booster shots are coming follows an announcement Monday night that the government would offer vaccines to all children ages 12 to 15.

Speaking in the House of Commons, Javid said some of the emergency powers Parliament introduced in 2020 as Britain went into the first of its pandemic-induced lockdowns would be repealed. But others would be kept as part of Plan B.

This included contingency measures such as legally mandating face masks — a remark that prompted one Conservative lawmaker to cry out “No!” — and pressing people to work from home. Javid also said that although plans to introduce vaccine passports in October for large gatherings have been paused, “we will be holding that power in reserve.”

At news conferences from 10 Downing Street on Monday and Tuesday, Prime Minister Boris Johnson and his scientific advisers stressed that the pandemic was ongoing and that the coming months would be about “living with the virus” and “getting through the winter.”

Johnson said it was vital to get the remaining vaccine holdouts — about 5 million people — to come forward to get vaccinated.