COVID-19 vaccine maker AstraZeneca announced Thursday that its antibody drug is more than 80% effective at reducing risk of severe disease or death. 

The company said new data from the AZD7442 COVID-19 Provent prevention and Tackle outpatient treatment Phase III trials showed "robust efficacy" from a one-time intramuscular dose of the long-acting antibody (LAAB) combination.

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Analysis of the ongoing Provent trial with a six-month follow-up found that one 300- mg intramuscular dose of AZD7442 reduced the risk of developing symptomatic COVID-19 compared to placebo by 83%.

"The AZD7442 PROVENT trial is the first Phase III trial prospectively designed to evaluate a monoclonal antibody for pre-exposure prophylaxis of symptomatic COVID-19, with targeted inclusion of high-risk and immunocompromised participants. More than 75% of PROVENT participants at baseline had co-morbidities that put them at high risk for severe COVID-19 if they were to become infected, including people who are immunocompromised and may have a reduced immune response to vaccination," AstraZeneca wrote

There were no cases of severe COVID-19 or COVID-19-related deaths in those treated with AZD7442 at either the initial or six-month analyses.

In this Wednesday, March 10, 2021, file photo, a health worker administers a dose of the AstraZeneca vaccine against COVID-19 to a patient inside the convention center known as

In this Wednesday, March 10, 2021, file photo, a health worker administers a dose of the AstraZeneca vaccine against COVID-19 to a patient inside the convention center known as "La Nuvola," The Cloud, in Rome.  (AP Photo/Andrew Medichini, file)

Comparatively, in the placebo arm, there were two additional cases of severe COVID-19 at the six-month assessment and five in total. There were also two COVID-related deaths.

An exploratory analysis of a separate treatment trial – the Tackle outpatient treatment trial – found that one 600-mg intramuscular dose of AZD7442 reduced the risk of patients with mild-to-moderate COVID-19 developing severe COVID-19 or death by 88%, compared with placebo in patients who had been symptomatic for three days or less at the time of treatment.

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AstraZeneca noted that 90% of the participants enrolled in Tackle were from populations at high risk of progression to severe COVID-19 if they became infected, including those with comorbidities.

"In both PROVENT and TACKLE, AZD7442 was generally well tolerated," it said. "No new safety issues were identified in the six-month analysis of PROVENT." 

"AZD7442 is the only long-acting antibody with Phase III data to demonstrate benefit in both pre-exposure prophylaxis and treatment of COVID-19 with one dose. These new data add to the growing body of evidence supporting AZD7442’s potential to make a significant difference in the prevention and treatment of COVID-19," Mene Pangalos, executive vice president of biopharmaceuticals research and development at AstraZeneca, said in a statement. "We are progressing regulatory filings around the world and look forward to providing an important new option against SARS-CoV-2 as quickly as possible."

The full results from both trials will be submitted for publication in a peer-reviewed medical journal and presented at a forthcoming medical meeting.

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In October, AstraZeneca announced that it had submitted a request to the Food and Drug Administration for Emergency Use Authorization for AZD7442 – or Evusheld – "for prophylaxis of COVID-19."

If regulators greenlight authorization, the company has agreed to supply the U.S. government with 700,000 doses of AZD7442.