AstraZeneca Plc and the University of Oxford’s COVID-19 vaccine won U.K. clearance, marking the first approval worldwide for a shot that’s faced questions but will be key to mass immunizations.

The vaccine will be prioritized for the country’s most vulnerable groups, with shots starting Monday, according to the government. It’s the second coronavirus injection to be cleared for emergency use in the U.K. after Pfizer Inc. and BioNTech SE’s in early December.

The move will help the U.K. ramp up vaccinations as a new surge in coronavirus infections strains hospitals. The country has reported record numbers of COVID cases this week, with a new variant of the pathogen raising concern globally.