Austrian district will study how the Pfizer vaccine works against a variant.

European authorities will offer a coronavirus vaccine to every adult in an Austrian district battered by a surge in infections to determine how effective the inoculation is against the variant first found in South Africa.

Starting next week, everyone aged 16 and older living in the Schwaz district, near the western Austrian city of Innsbruck, will be eligible for free shots of the vaccine from Pfizer-BioNTech, as part of the unique drive to learn more about fighting the variant.

The study in Austria is part of a much broader global effort to answer a crucial question as the virus mutates and new variants emerge: Do vaccinations designed last year work against more recent mutations? If not, scientists will have to keep developing new versions of the inoculations.

Laboratory studies have shown that some vaccines that work well against earlier variants are less effective — though they still offer significant protection — against the variant known as B.1.351, which was first found in South Africa in December and has become the dominant one there.

Real-world tests of those findings are still needed, and some combinations of variants and vaccines have not yet been tested, even in lab settings.

Authorities in the Schwaz district, in the state of Tyrol, appealed on Thursday to residents to sign up for their vaccines by March 8, to allow for enough doses to be ordered and delivered for the study. More than 20,000 residents, roughly a third of all those eligible, registered in the first 24 hours, the authorities said.

Earlier this week, Ursula von der Leyen, president of the European Commission, agreed to allocate 100,000 extra doses of the vaccine to Austria, in exchange for allowing a multinational team of scientists to collect data from the mass vaccination in Tyrol. The region has seen one of the worst outbreaks of the variant in Europe and Austria’s chancellor, Sebastian Kurz, had been lobbying the European Union for extra doses to try to stop its spread.

“Our goal is to be able to massively halt, if not eradicate, the South African variant,” Günther Platter, the governor of Tyrol, said on Wednesday. “We want to protect the people from this variant.”

But the success of the project is dependent on everyone being willing to take part. Officials hope to begin administering shots on March 11.