The vaccine developed by Oxford University was 90% effective in preventing COVID-19 when it was administered as a half dose followed by a full dose at least one month apart, according to data from the late-stage trials in Britain and Brazil.
No serious safety events related to the vaccine have been confirmed and it was well tolerated across both dosing regimens, it said.
“This vaccine’s efficacy and safety confirm that it will be highly effective against COVID-19 and will have an immediate impact on this public health emergency,” Pascal Soriot, Astra’s chief executive, said in a statement.
AstraZeneca will have 200 million doses by the end of 2020, with 700 million doses ready globally by the end of the first quarter of 2021, operations executive Pam Cheng said on Monday.
The vaccine’s effectiveness depended on the dosing, and fell to just 62% when given as two full doses rather than a half-dose first. But scientists cautioned against seeing this as evidence that it would be less useful than rival vaccines from Pfizer and Moderna, which each prevented about 95% of cases according to interim data from their late-stage trials.
“I think it is a real fool’s errand to start trying to pick these three (Pfizer/Moderna/Astra) apart on the basis of snippets of phase 3 data from press releases,” said Danny Altmann, professor of immunology at Imperial College London.
“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% protection - and we’ll be a lot happier.”
Scientists also noted there may be advantages to AstraZeneca’s vaccine.