LONDON -- British government regulators on Friday authorized another coronavirus vaccine for use in the U.K. amid concerns about rising COVID-19 cases as a variant of the virus first identified in India spreads around the country.

The Medicines and Healthcare products Regulatory Agency said the single-dose vaccine made by Johnson & Johnson met “the expected standards of safety, quality and effectiveness.â€

The authorization takes the number of vaccines in the U.K.'s armory to four following earlier approvals for the two-dose regimens developed by Pfizer/BioNTech, AstraZeneca and the University of Oxford, and Moderna.

The regulator said the vaccine developed by J&J subsidiary Janssen has been shown to be 67% effective overall in preventing COVID-19 infection and 85% effective in preventing severe disease or hospitalization. It can be be stored at refrigerator temperatures of 2 to 8 degrees Celsius (36 to 47 F), which the regulator said makes it “ideal for distribution to care homes and other locations.â€

Details of which groups will get the vaccine have yet to be determined. There was speculation it might only be administered to older adults after it was linked to reports of rare blood clots.

Given the U.K.'s rapid rollout of vaccines, the Johnson & Johnson's product may be used as part of the country's planned booster program in the fall. The Joint Committee on Vaccination and Immunisation, which decides how vaccines are rolled out across the U.K., will submit updated advice before the shots become available.

The British government has amended its order from last year of 30 million J&J doses to 20 million.

“As Janssen is a single-dose vaccine, it will play an important role in the months to come as we redouble our efforts to encourage everyone to get their jabs and potentially begin a booster program later this year,†Health Secretary Matt Hancock said.

Nearly 58% of the population has received at least one dose and around 35% has gotten two shots. The U.K. is aiming to have offered a jab to all adults by the end of July.

The U.K. has seen a modest uptick in new cases in recent days as a result of the variant identified in India, which is considered to be more transmissible than the previously dominant strain of the virus.

On Thursday, the country reported 3,542 new confirmed cases, its highest daily total since April 12. The number of cases remains well below the close to 70,000 recorded in mid-January, during the peak of the second wave.

Data released on Friday by the Department of Health and Social Care and the Scientific Advisory Group for Emergencies put the virus' reproduction number between 1.0 and 1.1, up from the previous week's 0.9 to 1.1. The new range means that every 10 infected people are likely to infect 10 or 11 others, meaning the outbreak is growing.

Concerns are mounting that the next scheduled easing of lockdown restrictions in England on June 21 will have to be delayed if case numbers continue to rise. The British government has said that it will make a decision on whether to lift all remaining social restrictions on June 14.

The government has been lifting restrictions in stages. Indoor eating, drinking and entertainment venues reopening last week, but social distancing and mask-wearing rules still in place.

While the most vulnerable people should have vaccine protection, there are worries the virus could spread widely among younger adults and that many will end up needing to go to the hospital.

Prime Minister Boris Johnson said Thursday that the decision to take the next step in his government's roadmap out of lockdown would depend on how much the new variant drove an increase in cases and the speed of the vaccination campaign.

“I don't see anything currently in the data to suggest that we have to deviate from the roadmap,†he said. “But we may need to wait.â€