BERLIN — 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, announcing the project on Wednesday. “We want to protect the people from this variant.”

The pilot program in Austria is the first such inoculation drive targeting a specific region within the European Union, where the vaccine rollout has lagged among member states, far behind some other wealthy nations. About 6 percent of the bloc’s people have received at least one shot, compared to 16 percent in the United States, 31 percent in Britain and 55 percent in Israel.

“From a scientific point of view, it is an unbelievably important study where we can learn a lot,” Dr. Herwig Kollaritsch, a member of Austria’s immunization commission, said in an interview with public broadcaster ORF.

“It will also be beneficial to Pfizer, which is legitimate because these vaccines have not been on the market for very long and every day we acquire more knowledge that helps us to understand how to best use them,” Dr. Kollaritsch said.

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

Dr. Kollaritsch said it would take roughly one month for the full effect of the vaccine to take hold. Teams of scientists from Austria and abroad will be monitoring how well the vaccine prevents infection with the variant, a scenario that has not yet been clinically tested, he said.

Since last February, thousands of police and border patrol officers have been securing the state’s border, ensuring that anyone leaving, even to travel to other regions in Austria, can produce a test showing they are not infected. Communities were provided with test kits to encourage widespread testing as part of tracing efforts to prevent the spread of the virus.

The state has seen the number of infections with the B.1.351 variant drop from 200 per day at the start of February to 88 on Wednesday, as the overall infection rate in the state has also continued to decline.

Wary of the threat posed by the variant, the German government closed its border with Tyrol last month, disrupting international travel on one of Europe’s most important north-south arteries, snarling traffic and angering authorities in Brussels.

The region has been one of Austria’s hardest hit by the coronavirus. The first cases of infection in the country were detected in the state capital of Innsbruck in February 2020. The following month, a superspreader event was traced to the ski resort town of Ischgl, where authorities later determined many Europeans contracted the virus while there on vacation, and then took it home with them.

Christopher F. Schuetze contributed reporting from Hanover, Germany