LONDON (AP) — British Prime Minister Boris Johnson warned Monday of a “blizzard” of new coronavirus infections coming into the U.K. from continental Europe, as his government extended the vaccine booster program to younger people in an effort to keep a lid on the pandemic during the winter months.

The Joint Committee on Vaccination and Immunization, the independent body of scientists that makes vaccine recommendations to the British government, said people aged 40 to 49 will also be eligible for a vaccine booster shot six months after their initial shot. Up until now, people aged 50 and over, as well as those deemed to be vulnerable in younger age groups, had been eligible for Pfizer or Moderna vaccine boosters.

The committee said that second doses of the Pfizer vaccine have also been approved for 16 and 17-year-olds 12 weeks after their first.

It said the the broadening of the booster campaign and the offer of a second jab to older teens will “help extend our protection into 2022."

Johnson urged people to get their booster to get the extra level of protection amid growing concerns of the virus outlook in Europe following fresh lockdowns in Austria and the Netherlands.

“What we have certainly got to recognize is there is a storm of infection out there in parts of Europe, you can see those numbers ticking up very sharply in some of our continental friends," he said. “And we’ve just got to recognize that there is always a risk that a blizzard could come from the east again, as the months get colder.”

Over the past few months, the U.K. has recorded relatively high levels of coronavirus infections following the lifting of most restrictions.

Though cases have steadily fallen in recent weeks, there have been signs over the past few days that they are ticking up again, particularly among students. Over the past week, there have been more than 260,000 confirmed infections, up 6% on the previous week.

The government has so far resisted reimposing restrictions such as mask-wearing in indoor places or introducing vaccine passports.

Johnson said there was nothing currently in the data which suggested a need to increase restrictions in England, under its contingency Plan B. The number of people in hospital with the virus is around 8,500, which though high is far down on the near 40,000 in January. Virus-related deaths are at around 150 a day.

“What’s happening is if you can get your booster then your immunity goes right back up to 95%," he said. “So far we’ve got 75% of everybody over 70 getting a booster, there’s a huge number of people, but it’s that further 25% that will make all the difference to winter, to Christmas, to our plans going forward, because it’s that extra level of protection that we really need.”

The expansion of the booster program comes as a new study from the U.K. Health Security showed adults over 50 had at least 93% reduced risk of getting a symptomatic case of COVID-19 two weeks after their booster.

“The booster dose markedly strengthens existing protection and will extend the duration of that protection against serious disease," said Professor Wei Shen Lim, chair of the JCVI's COVID-19 immunization program.

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