AstraZeneca (NASDAQ: AZN) reported on Monday that its coronavirus vaccine candidate developed in partnership with the University of Oxford was found to be 79% effective in preventing symptomatic infection and 100% effective at preventing severe disease and hospitalization in its late-stage U.S. clinical trial.
The vaccine's new safety and efficacy analysis was based on 32,449 healthy, adult participants across dozens of trial centers in the United States, Peru and Chile. While the vaccine's efficacy was consistent across both ethnicity and age, the vaccine had a higher efficiency for participants aged 65 years or older, being 80% effective against severe disease.
The trial data also demonstrated that the vaccine was well tolerated in participants and raised no safety concerns regarding blood clots, medically known as thrombosis. These results come after several counties had temporary paused their use of the vaccine following concerning reports that the shot may be linked to increased risk of blood clots.
AstraZeneca said that the trial's independent data safety monitoring board (DSMB) found "no increased risk of thrombosis of events characterised by thrombosis among the 21,583 participants receiving at least one dose of the vaccine." The DSMB, with the help of an independent neurologist, also analyzed for a more serious form of blood clots that are present around the brain, known as cerebral venous sinus thrombosis, and found no evidence linking the vaccine to this condition.
Multiple countries, including Germany, France, Italy and Spain have resumed use of the AstraZeneca vaccine after the European Medicines Agency, the region's drug regulator, found the vaccine to be safe and effective upon further data analysis. The World Health Organization as well as the International Society on Thrombosis and Hemostasis also recommend use of the vaccine.
The pharmaceutical giant said that it will continue to analyze the data from the trial and prepare for the primary analysis to be submitted to the U.S. Food and Drug Administration in request of an emergency use authorization in the company weeks. The analysis will also be submitted for publication in a peer-reviewed journal.
The United States has been critical of the AstraZeneca-Oxford vaccine candidate in the past, with this trial the result of many global health experts and regulators requesting clarity from the results of the drugmaker's first late-stage trial released last November. Those trials, which were conducted in the United Kingdom and Brazil, produced different efficacy ratings due to different dosing amounts and regimes used by researchers. The vaccine requires two doses given a few weeks apart.
However, the vaccine may still have trouble with getting approval in the United States even with the new trial data.
On Tuesday, the U.S. National Institute of Allergy and Infectious Diseases said in a statement that AstraZeneca may have included outdated information in its new trial results, "which may have provided an incomplete view of the efficacy data."
In response to the health agency, AstraZeneca issued in a statement on Tuesday: "We will immediately engage with the independent data safety monitoring board to share our primary analysis with the most up to date efficacy data. We intend to issue results of the primary analysis within 48 hours."