Britain’s health secretary is urging eligible residents to get booster shots of the coronavirus vaccine, aiming to reduce pressure on the country’s health system as winter approaches.

Ten million Britons, largely those over age 50, have received booster shots since the government began offering them, and millions more will be invited in the coming weeks to book appointments.

Officials hope the extra doses will boost protection against the virus. Some research suggests that immunity against infection in certain populations, particularly the elderly and those with underlying medical conditions, may begin to wane six months after full vaccination.

“If we all come together and play our part, we can get through this challenging winter, avoid a return to restrictions and enjoy Christmas,” said Sajid Javid, the health secretary, in a statement on Sunday.

The move recalled last winter’s outbreak, when the Alpha variant ripped through the country, prompting dozens of nations to ban British travelers and forcing families to cancel Christmas gatherings because of lockdown restrictions.

As Britain and several European countries struggle with a surge in cases, the World Health Organization said this week that Europe has reemerged as an epicenter of the pandemic and could experience a half million Covid-related deaths in the next three months.

The region was reporting an average of more than 30 new cases a day for every 100,000 people, a rate that has almost doubled since mid-September. Officials have blamed the relaxation of coronavirus restrictions and low vaccination rates in some countries.

Germany, where vaccination rates are lagging behind those in such European countries as Spain and Italy, reported a new daily case record this week, with about 25,320 infections on average per day. Some 67 percent of the population is fully vaccinated.