AstraZeneca AZN -0.24% PLC’s Covid-19 vaccine was shown to be safe and 79% effective in preventing symptomatic disease in U.S. clinical trials involving more than 32,000 people, the U.K. drugmaker said Monday.
The company said it would continue to analyze the data and prepare to request emergency authorization in the U.S. in coming weeks, a move that—if approved—will add another vaccine available for Americans.
The shot is already widely used outside the U.S. The American trials, however, reflect the largest-scale tests yet of the vaccine and could bolster confidence in its use following questions about its efficacy and serious blood-clotting issues in a very small number of people in Europe who received the shot. The U.S. trials identified no increased risk of serious blood clotting.
AstraZeneca said participants aged 65 years and over were shown to have vaccine efficacy of 80%.
Blood clotting concerns led more than a dozen European countries, including Germany and Italy, to temporarily halt use of the vaccine this month. Most resumed administering the vaccine after European and U.K. medicine regulators again endorsed the shot’s use despite the rare clotting issues, which weren’t proven to be linked to the vaccine. The regulators said they couldn’t rule out a connection, but said the vaccine is an important weapon in preventing death and serious illness and that its benefits outweigh potential risks.
Much is riding on global acceptance of the AstraZeneca shot, which was co-developed with the University of Oxford and is the most widely used in many parts of the globe. The U.S. Food and Drug Administration is expected to review the trial data and could decide whether to authorize the vaccine for use as early as next month.
Previous trial results of the shot from the U.K. and elsewhere were criticized for lacking elderly volunteers, who were recruited later in the trial process for safety reasons. The U.K. and other countries used the vaccine in over-55s, but some countries initially held back and only deployed the shot in younger age groups.
The U.S. trial involved 32,449 participants aged 18 and over, and about 20% were 65 or older. The vaccine’s effectiveness was 100% in preventing severe disease and hospitalizations, with similar results across all age and ethnicity groups.
The U.K. trial results of the vaccine, released late last year, presented a range of effectiveness, between 62% and 90%. That range was difficult to compare with U.S. trial results of rival vaccines, one from Pfizer Inc. and Germany’s BioNTech SE and another from Moderna Inc. Both were found to be more than 90% effective in U.S. trials.
The U.S. trial results haven’t yet been reviewed by independent researchers. AstraZeneca said the analysis will be submitted for publication in a peer-reviewed journal.
AstraZeneca said independent safety monitors ran a specific review of severe blood clotting, or serious thrombotic events, based on the trial data, including a severe condition known as cerebral venous sinus thrombosis that has been reported to be linked to a very small number of deaths in Europe among people who received the vaccine. The review was assisted by an independent neurologist. It found no increased risk of thrombosis among 21,583 participants who received at least one dose of the vaccine, AstraZeneca said.
The U.S. AstraZeneca vaccine trial, which started recruiting volunteers in the U.S., Chile and Peru in August, was standardized to meet FDA guidelines, measuring the results of two doses four weeks apart. AstraZeneca said stretching out doses—which the U.K. and other countries have done—could boost effectiveness of the vaccine further.
Write to Jenny Strasburg at [email protected]
Copyright ©2020 Dow Jones & Company, Inc. All Rights Reserved. 87990cbe856818d5eddac44c7b1cdeb8
