AstraZeneca vaccine 79% effective in US trial with no identified safety concerns
[Editor’s note: A data and safety monitoring board has “expressed concern” that AstraZeneca may have reported outdated information from this trial. For more on that story, click here.]
AstraZeneca’s COVID-19 vaccine demonstrated an overall efficacy of 79% against symptomatic disease and completely prevented severe disease or hospitalization in a trial conducted partly in the United States, the company said Monday.
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That overall efficacy number is higher than the average efficacy reported from trials of the vaccine in the United Kingdom and Brazil last year.
An independent review by the data safety monitoring board identified no safety concerns in the new trial, including no increased risk for thrombosis or “events characterized by thrombosis” among more than 21,500 people who had received at least one dose of the vaccine, AstraZeneca said.
Ann Falsey, MD, professor of medicine at the University of Rochester School of Medicine and co-lead principal investigator for the trial, reiterated during a call with reporters that a close look at the data showed “no concerning signals” regarding the risk for thrombosis.
The European Medicines Agency last week declared the AstraZeneca shot safe after several European countries halted their rollout of the vaccine over reports of blood clots in vaccinees.
The vaccine has already been authorized for use in more than 70 countries. Ruud Dobber, PhD, who leads AstraZeneca’s biopharmaceuticals business unit, said during Monday’s press call that the company would submit the vaccine to the FDA for emergency use authorization (EUA) in the U.S. in the first half of April. He said the company would have 30 million doses available right away and 20 million more soon after that, for a total of 50 million doses ready to be shipped in the U.S. in the first month after the issuance of an EUA.
The U.S. has administered nearly 124.5 million doses of the three already available COVID-19 vaccines, with more than 44 million people already fully vaccinated, according to CDC tracking.
Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, said the AstraZeneca vaccine “would be an important addition to the U.S. COVID-19 vaccine menu.”
“There are many people left to vaccinate and the stockpiles of tens of millions of doses could be rapidly mobilized. Vaccination with no speed limit is the goal,” he told Healio.
The new efficacy data were based on a phase 3 trial that included more than 32,000 participants enrolled from 88 locations in the U.S., Chile, and Peru, and assigned in a 2 to 1 ratio to receive either the vaccine, which is called AZD1222, or a placebo. In addition to the overall efficacy result, the trial also showed that the vaccine was 80% efficacious in adults aged older than 65 years.
The calculated overall efficacy was based on 141 symptomatic cases of COVID-19 diagnosed among trial participants. Investigators on the call with reporters were not able to provide a breakdown of how many cases occurred in each arm of the trial, nor did they have data yet about how the vaccine performed against SARS-CoV-2 variants, although Falsey said they were “optimistic” for positive outcomes in that regard and AstraZeneca executive vice president of biopharmaceuticals R&D Mene Pangalos said they were encouraged by the results given that the trial took place in areas where variants are circulating.
The second dose in the trial was administered 4 weeks after the first, but previous data indicate that the vaccine is even more efficacious when the doses are given at even larger intervals — up to 12 weeks, the company said. This could increase the number of people who can receive their first dose sooner.
The chimpanzee adenovirus-vectored vaccine can be transported and stored at normal refrigerated temperatures for at least 6 months and administered within existing health care settings without a need for special preparations, the company noted.
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