LONDON — Britain is to expand the rollout of its coronavirus vaccine program by offering jabs to those over the age of 70 in areas where those deemed to be the most vulnerable have already received their first dose.

More than 3.8 million people across the U.K. — more than 5% of the population — have already received their first dose of vaccine.

The early phase of the vaccination program has been focused on the most vulnerable groups — those over the age of 80, residents in nursing homes and their carers, and staff in hospitals.

Britain is also opening another 10 mass vaccination centers this week. And a pilot program to provide 24-hour vaccinations will commence in London hospitals by the end of January.

Britain’s vaccines minister, Nadhim Zahawi, said the normal daytime slots work “much more conveniently” for those over the age of 80 but that nighttime appointments may be handier for those in lower age groups.

Britain, which has Europe’s highest virus-related death toll at nearly 90,000, is aiming to have offered a first dose of vaccine to the four groups deemed most vulnerable to COVID-19 by mid-February.