AstraZeneca's Covid-19 vaccine showed 79% efficacy against symptomatic disease and 100% efficacy against severe disease and hospitalization in a new, US-based clinical trial, the company said Monday.
The findings from the new Phase 3 trial, which included more than 32,000 participants, may boost confidence in the vaccine, which was originally developed by the University of Oxford.
The trial showed that the vaccine was well-tolerated and identified no safety concerns, the company said. An independent committee "found no increased risk of thrombosis or events characterized by thrombosis among the 21,583 participants receiving at least one dose of the vaccine," according to AstraZeneca.
The new data came from a Phase 3 clinical trial conducted in the US, Chile and Peru. AstraZeneca says it plans to submit the findings to a scientific journal for peer review.
Ruud Dobber, president of AstraZeneca's biopharmaceuticals business unit, said on CNBC Monday that the company plans to apply for emergency use authorization from the US Food and Drug Administration in the first half of April. If authorized, it would be the fourth Covid-19 vaccine available in the United States.
For its part, Oxford said the findings add "to previous trial data from the United Kingdom, Brazil and South Africa, as well as real-world impact data from the United Kingdom" according to a press release from the university.
As part of the trial, more than 32,000 adult volunteers recruited across all ages received either two doses of the vaccine or a placebo vaccine at a four-week interval.
About 79% of trial participants were White, 22% were Hispanic, 8% were Black, 4% were Native American and 4% were Asian.
About 20% of participants were 65 years and over and approximately 60% had conditions linked with higher risk of severe Covid-19, such as diabetes, severe obesity or heart disease.
In patients 65 years and older, vaccine efficacy was 80%, AstraZeneca said -- echoing the overall trial results -- which is notable as some countries initially did not authorize the vaccine for use in this older age group, citing a lack of data from earlier trials.
"It is clear this vaccine has very good efficacy (remember that 60% was, prior to any trials being started, regarded as a good target), and that this efficacy does not show a notable decline at older ages," Stephen Evans, a professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine, said in a statement to the Science Media Centre in the UK.
Evans called previous assertions that the vaccine may be ineffective in older ages"totally unjustified."
The Oxford-AstraZeneca vaccine became the subject of controversy earlier in the month when a number of European countries including Norway, France and Denmark decided to temporarily suspend its rollout due to reports of blood clotting in patients post inoculation.
An emergency investigation by the European Medicines Agency (EMA) came to the conclusion last Thursday that the vaccine is "safe and effective" in preventing coronavirus and "not associated with an increase in the overall risk of thromboembolic events, or blood clots."
Lead Investigator for the vaccine and professor of Paediatric Infection and Immunity at Oxford University Andrew Pollard said the AstraZeneca data was "consistent with the results from Oxford-led trials," adding that he expected a "strong impact against COVID-19 across all ages and for people of all different backgrounds from widespread use of the vaccine."
Dr. Peter Hotez, dean for the National School for Tropical Medicine at the Baylor College of Medicine, told CNN's Alisyn Camerota the results were good news for the United States and the world.
"I'm pretty confident now AstraZeneca will apply for, request emergency use authorization, so we'll have that vaccine released to the American public," Hotez said. Covid-19 vaccines by Pfizer/BioNTech, Moderna and Johnson & Johnson have previously been authorized in the United States.
Despite recent pauses in the vaccine's rollout, "this is one of our workhorse vaccines that we're expecting for Africa and Latin America," Hotez said. "So this is good news also because it's reaffirming for the vaccines used for global health as well."