U.K. approves the use of the Johnson & Johnson vaccine.

Britain’s drug regulator on Friday approved the use of the single-dose shots manufactured by Johnson & Johnson, the fourth coronavirus vaccine to be authorized in the country.

The authorization comes amid growing concerns about the spread in Britain of a coronavirus variant first detected in India. The number of cases of the variant, known as B.1.617.2, has doubled in a week, according to public data, and as of Thursday, nearly 7,000 cases had been detected.

“This fourth approved vaccine adds to our armory,” the British health secretary, Matt Hancock, said on Twitter. “When you’re eligible, get your jab.” Britain has also authorized the use of the vaccines manufactured by Moderna, Oxford-AstraZeneca and Pfizer-BioNTech.

More than 58 percent of Britain’s population has received at least one dose of a coronavirus vaccine, and 36 percent has been fully vaccinated. Britain opened vaccination to adults 30 and older this week, but most of the vaccination campaign’s efforts have in recent weeks focused on second injections.

Johnson & Johnson’s vaccine is 85 percent effective against severe illness from Covid-19, according to the British regulator.

The approval in Britain comes a day after Mexico gave emergency authorization to the same vaccine.

The Mexican government has previously authorized the vaccines from AstraZeneca and Pfizer, as well as Russia’s Sputnik V and China’s Sinovac and CanSino.

In other news around the world:

• Hong Kong on Thursday recorded no new coronavirus cases for the first time in seven months, a promising sign in the Chinese territory’s efforts to quash a wave of infections that began in November. The city has gone more than a month without recording more than 15 daily cases, increasing calls for the authorities to relax social-distancing measures.

• Vietnam ordered religious establishments to suspend large gatherings after a cluster of infections was linked to a Protestant congregation in Ho Chi Minh City, part of a nationwide surge in cases. Of more than 6,300 total cases recorded in the Southeast Asian nation since the start of the pandemic, half have come in the past month, the state-run Vietnam News Agency reported.

• South America’s largest soccer tournament is scheduled to start in just over two weeks, but with one of the planned host countries, Colombia, removed because of political protests, and the remaining host, Argentina, mired in its worst coronavirus surge to date, it is unclear where the competition will take place.