Prime Minister Boris Johnson of Britain received his first dose of AstraZeneca’s coronavirus vaccine on Friday, as neighboring countries resumed its use after the European Union’s drug regulator ruled it safe and effective.

“Getting the jab is the best thing we can do to get back to the lives we miss so much,” said Mr. Johnson after receiving his first injection at St Thomas’ Hospital in London, where he spent three nights in intensive care last year as he battled persistent symptoms of the Covid-19.

“Thank you to all the incredible scientists, NHS staff and volunteers who helped make this happen,” Mr. Johnson, 56, added about the revered National Health Service.

hampered by a drop in vaccine supply.

nearly 126,000.

But British authorities hope that the breakneck pace of their vaccination campaign will help the country return to some form of normalcy by the summer.

Schools reopened this month, and more restrictions are expected to be lifted in the spring. Mr. Johnson insisted this week that the “road to freedom remains unchecked” despite the announced shortage in vaccine supply.

the variant first discovered in South Africa.

Early research suggests that the variant, which accounts for a significant portion of new cases in countries like France, may weaken the efficacy of some vaccines. That includes the AstraZeneca vaccine, which is central to Britain’s inoculation drive.

The head of England’s National Health Service, Simon Stevens, 54, also received his first injection of the AstraZeneca vaccine this week, as did Prime Minister Jean Castex of France, 55, who flashed a thumbs-up at television cameras after getting his shot at a military hospital southeast of Paris.

The nearly simultaneous public inoculations of Mr. Johnson and Mr. Castex underscored how public officials in Europe have tried to restore public confidence in the AstraZeneca vaccine, after several countries in the European Union, including France, paused its use this week.