British-Swedish pharmaceutical company AstraZeneca announced on Monday its antibody-drug Evusheld, which is taken pre-emptively to prevent Covid-19, has been approved in the European Union.

The treatment, administered in two injections, can be taken by adults and adolescents above the age of 12. In clinical trials, the drug reduced the risk of developing symptomatic Covid-19 by 77% compared to the placebo, the company said in a statement.

Unlike other antibody treatments, which are used after someone contracts Covid-19 to prevent severe illness, Evusheld would be used as an alternative vaccination for people who had a weak immune response to existing Covid-19 vaccines or for whom vaccination is not recommended, such as the immunocompromised.

In a second analysis, six months into the Phase 3 trial of Evusheld - which includes a 150mg dose of tixagevimab and 150mg of cilgavimab administered as two separate sequential injections - those who took the drug saw their risk of developing symptomatic Covid-19 drop by 83% compared to those who'd taken a placebo.

The company also said Evusheld specifically targeted and neutralized antibodies from Omicron and its subsequent BA.2 variant, which is now dominant across Europe and the U.S.

Christoph D. Spinner, pandemic officer at the University Hospital Rechts der Isar, said, “the authorization of Evusheld for a broad population will allow health authorities in the EU to identify the populations who are most at-risk and need additional protection.”

Confusion overseas

Evusheld was authorized by the Food and Drug Administration on Feb. 2, 2022 for emergency use in the U.S. and has also been granted conditional marketing authorization in the U.K.

But while the protection it offers from getting Covid-19 is widely accepted, around 80% of the available Evusheld doses sit unused in warehouses, pharmacies and hospitals, according to the New York Times.

In the U.S., there has been confusion surrounding the drug, with patients and doctors not knowing about the drug’s existence or where they can even find it. Some doctors and providers also don’t know how to prescribe the drug due to its confusing relationship to other antibody therapies that are usually taken after contracting Covid-19.

“The biggest problem is that there is absolutely no guidance or prioritization or any rollout in place at all, and it’s been a mess,” Dr. Dorry Segev, a transplant surgeon and epidemiologist at N.Y.U. Langone Health, said in the New York Times.

"For people who did everything they could but didn't have an adequate response to the vaccines, [Evusheld] is their only hope, and to deny them that because of a disorganized and chaotic distribution and education rollout is just terrible," Sergev said to CNN.

The Biden administration purchased 1.7 million doses of Evusheld in January - enough to fully treat 850,000 people - and made 650,000 doses ready for distribution to the states. But of those 1.7 million doses only 370,000 have been ordered by the states, and fewer than a quarter of those doses have been used.

A CNN investigation identified 59 pharmacies that had ordered Evusheld. Of the 5,372 boxes they had been delivered, only 1,376 boxes had been used.

Distributing Evusheld in the EU will likely require a smoother rollout to avoid the poor uptake it has experienced in the U.S. "We will continue to work with governments across Europe to make Evusheld available as quickly as possible," Mene Pangalos, executive vice president of biopharmaceuticals research and development at AstraZeneca said.

Otherwise, the immunocompromised waiting for a silver bullet may be left waiting.

This story was originally featured on Fortune.com