Drugmaker AstraZeneca announced Monday morning that its vaccine candidate, developed by Oxford University, is up to 90 percent effective in preventing COVID-19, the third such candidate to meet the threshold.
The company said an interim analysis of U.K. trials found an average efficacy rate of 70 percent, seemingly less effective than two other vaccines from Moderna and the Pfizer/BioNTech group.
It said two full doses of the vaccine given at least a month apart appeared to be only 62 percent effective at preventing disease, while a half dose followed by a full dose was about 90 percent effective.
“We’ve found that one of our dosing regimens may be around 90 percent effective and if this dosing regime is used, more people could be vaccinated with planned vaccine supply,” Andrew Pollard, CEO of the Oxford Vaccine Trial, said in a statement. “Today’s announcement is only possible thanks to the many volunteers in our trial, and the hard working and talented team of researchers based around the world.”
The reasons for the difference will not likely be known until the full data are published in a medical journal.
The U.S. clinical trial, funded by the Trump administration's Operation Warp Speed, is testing the full two-dose regimen.
AstraZeneca said no severe cases of the virus or hospitalizations were found among subjects receiving the vaccine, adding that it will seek emergency authorization in countries that allow for conditional approval.
Results in the U.S. will likely be delayed, however, as the clinical trial was paused for over a month because one of the participants developed a neurological condition. The trial was just resumed last month.
AstraZeneca reportedly said it could have up to 200 million doses by the end of the year, around quadruple that of Pfizer. The company also said it could manufacture up to 3 billion doses worldwide by the end of 2021 on a rolling basis.
Pollard noted in a news conference that the vaccine could also be stored at refrigerated temperatures, simplifying the logistics of transporting it.
“Because the vaccine can be stored at fridge temperatures, it can be distributed around the world using the normal immunization distribution system,” he said in a news conference. “And so our goal … to make sure that we have a vaccine that was accessible everywhere, I think we’ve actually managed to do that.”
Aside from being easier to store and distribute, the vaccine is also expected to be cheaper than the others. AstraZeneca has pledged to sell the drug at cost.
Experts told Reuters that the latest data should not be taken as an indication that AstraZeneca's vaccine is less effective than its counterparts from Pfizer and Moderna, which both recently reported 95 percent efficacy rates.
“I think it is a real fool’s errand to start trying to pick these three apart on the basis of snippets of phase three data from press releases,” Danny Altmann, a professor of immunology at Imperial College London, told the news service. “For the bigger picture, my suspicion is that by the time we are a year down the line, we’ll be using all three vaccines with about 90 percent protection — and we’ll be a lot happier.”
— Updated at 9:29 a.m.