After months of research and a week-long controversy over a reduction in expected vaccine supply, regulators in Europe have authorized AstraZeneca’s two-dose COVID-19 vaccine.
The vaccine, the result of AZ's collaboration with Oxford University, is conditionally approved across Europe in people ages 18 and older. A broad rollout in EU member countries will follow, but in recent days, a reduction in first-quarter supply has dominated headlines.
Last week, AstraZeneca notified EU officials of manufacturing problems in its supply chain that would cause it to drastically cut first-quarter shipments to the continent. An intense back-and-forth followed, and on Friday, Europe restricted exports of COVID-19 vaccines.
On a call with reporters Friday, AstraZeneca CEO Pascal Soriot said that manufacturing processes typically take years to develop and refine. During the pandemic, the company and its production partners have set up the manufacturing process in the span of “a few months.” The result is that millions of doses will be available sooner, he said, but still the process hasn't been fully refined at all of the sites.
Some sites are farther along in the “learning curve," he said, so AZ is seeing a “variability of yield” throughout different sites in its network. The company has had a “good discussion” with Europe and is focused on improving supply, he said.
The AstraZeneca authorization follows similar green lights from European officials for mRNA vaccines from Pfizer/BioNTech and Moderna. But while those vaccine regimens require doses to be given several weeks apart, AZ's shots can be administered between 4 and 12 weeks part, providing for greater flexibility, Soriot noted.
That means if AZ ships an initial 20 million doses, European health officials could use all of them to start to vaccinate 20 million people, he said. Then, up to three months later, those recipients could get their second shots from another shipment.
In its phase 3 trial, AstraZeneca’s vaccine was 70% effective overall, but a dosing error yielded a higher result in a subset of participants. For people who received a half dose followed by a full dose, vaccine efficacy was 90%.
The trial results prompted AZ to run another study for a potential emergency use authorization in the U.S. That study is fully enrolled and set to read out next month, AZ execs said on Friday’s call.