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The drugmaker AstraZeneca announced on Monday that an early analysis of some of its late-stage clinical trials, conducted in the United Kingdom and Brazil, showed that its coronavirus vaccine was 70.4 percent effective in preventing Covid-19, suggesting that the world could eventually have at least three working vaccines — and more supply — to help curb the pandemic.
The British-Swedish company, which has been developing the vaccine with the University of Oxford, became the third major vaccine developer in this month to announce encouraging early results, following Pfizer and Moderna, which both said that their vaccines were about 95 percent effective in late-stage studies.
AstraZeneca’s results are a reassuring sign of the safety of the vaccine. It came under global scrutiny after AstraZeneca temporarily paused its trials in September to investigate potential safety issues after a participant in Britain developed a neurological illness.
Oxford and AstraZeneca said they would submit their data to regulators in Britain, Europe and Brazil and seek emergency authorization.
The company said its early analysis was based on 131 coronavirus cases. The trials used two different dosing regimens, one of which was 90 percent effective in preventing Covid-19 and the other of which was 62 percent effective.
The regimen that was 90 percent effective involved using a halved first dose and a standard second dose. Oxford and AstraZeneca also said that there were no hospitalized or severe cases of the coronavirus in anyone who received the vaccine, and that they had seen a reduction in asymptomatic infections, suggesting that the vaccine could reduce transmission.
AstraZeneca’s vaccine is expected to come with relatively simple storage requirements, which would be an asset once it gets rolled out. The company has said it anticipates the vaccine will require refrigeration, though it has not provided details about how long and at what temperature it can be kept. Moderna’s vaccine can be kept for up to a month at the temperature of an ordinary refrigerator. Pfizer’s can be kept for up to 5 days in conventional refrigerators, or in special coolers for up to 15 days, but otherwise needs ultracold storage.
AstraZeneca has said it aims to bring data from its studies of its vaccine being conducted overseas to the Food and Drug Administration — which would mean that the agency will likely review and authorize a vaccine before late-stage data are ready on how well the vaccine works in American participants. British regulators already have been conducting a so-called rolling review of the vaccine.
“Today marks an important milestone in our fight against the pandemic,” AstraZeneca’s chief executive, Pascal Soriot, 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.”
Professor Andrew Pollard, the chief investigator of the Oxford Vaccine Trial, said that “these findings show that we have an effective vaccine that will save many lives.”
In the wake of results suggesting that two prospective coronavirus vaccines are remarkably effective, the official in charge of the federal coronavirus vaccine program explained on Sunday news shows how the vaccines might be distributed to Americans as early as next month.
Dr. Moncef Slaoui, head of the administration’s Operation Warp Speed, said that within 24 hours after the Food and Drug Administration approves a vaccine, doses will be shipped to states to be distributed. “Within 48 hours from approval,” the first people would likely receive injections, Dr. Slaoui said on ABC’s “This Week With George Stephanopoulos.”
Two companies, Pfizer and Moderna, announced this month that their vaccines were about 95 percent effective, and Pfizer formally submitted an application to the F.D.A. for emergency approval. Regulators at the agency will spend about three weeks reviewing the application. On Dec. 10, an outside advisory board on vaccines will meet to discuss the application, and the agency is expected to make a decision shortly after that meeting. Moderna is expected to submit its own application soon.