AstraZeneca 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.