AstraZeneca's (AZN  ) new antibody therapy reduced the risk of people developing COVID-19 symptoms by 77% in a late-stage trial, the company announced Friday. This positive data now puts the drugmaker on track to not only offer an effective COVID-19 vaccine, but also a protective therapy for those who respond poorly to vaccines.

The company's antibody therapy, AZD7442, which consists of two types of COVID antibodies discovered by Vanderbilt University Medical Center licensed by AstraZeneca, was first designed to aid immune system response after COVID exposure or infection, similar to therapies developed by Regeneron (REGN  ) and Eli Lilly (LLY  ). However, after failing late-stage clinical trials, AstraZeneca then studied AZD7442's potential use at preventing COVID-19 symptoms, similar to a vaccine.

In a late-stage trial testing the combination antibody therapy as a preventative treatment, the company found in preliminary results that AZD7442 showed 77% efficacy in reducing risk of symptomatic COVID-19 compared to placebo.

According to the preliminary findings, about 75% of the trial's nearly 5,200 adult participants have comorbidities, or chronic diseases, including conditions that cause vaccines to be less effective, AstraZeneca said in a statement.

In the trial, two-thirds of participants received the therapy, which is injected, while the rest received an inert placebo. Of participants who received the drug, none developed severe COVID symptoms, while the placebo group recorded three severe cases and two fatalities. The drug was well tolerated by all those who received it, the company said.

The full trial results have yet to be published or peer reviewed. The company estimates that the protection offered by AZD7442 could last as long as a year, but more research is needed to determine the drug's long-term efficacy.

"We need additional approaches for individuals who are not adequately protected by COVID-19 vaccines," said Mene Pangalos, executive vice president at BioPharmaceuticals R&D, in a press statement. "We are very encouraged by these efficacy and safety data in high-risk people, showing our long-acting antibody combination have the potential to protect from symptomatic and severe disease, alongside vaccines."

AstraZeneca plans to seek regulatory approval for AZD7442, which would offer a potential new alternative to vaccines for those who are immunocompromised or for whom vaccines are less effective.

The combination antibody therapy is separate from AstraZeneca's COVID vaccine developed in partnership with the University of Oxford, which has been authorized for emergency use by the United Kingdom, European Union, the World Health Organization, and other global health regulators.