AstraZeneca says its COVID-19 vaccine is 79 percent effective in large U.S. trial

AstraZeneca and Oxford University said Monday that their COVID-19 vaccine proved to be 79 percent effective against symptomatic illness and 100 percent effective at preventing serious COVID-19 cases or hospitalization in a U.S. trial involving more than 30,000 people. The vaccine, tested on 32,559 people 18 and older was effective among all age groups and demographics, including 80 percent effective with participants 65 and older.

The U.S. trial's independent safety monitors, aided by an outside neurologist, specifically reviewed the trail data for increased risk of severe blood clotting, following reports of vaccinated people in Europe suffering from cerebral venous sinus thrombosis. The review found no increased risk of thrombosis in the 21,583 volunteers who received at least one dose of the vaccine; the other participants were given a placebo.

A YouGov poll published Monday found that a growing number of adults in Spain, Germany, France, and Italy believe the AstraZeneca vaccine is unsafe, following a brief suspension of the vaccine in those countries last week. They began using the vaccine again after the European Medicines Agency and World Health Organization affirmed that AstraZeneca's vaccine is safe and effective.

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Public confidence in this vaccine, developed by Oxford researchers, is especially important for the global vaccination effort. The vaccine is already the most-used shot in many countries, and largely because of its price — about $4 a dose — and ability to be stored in a normal refrigerator, it is central to the efforts to vaccinate the developing world.

The U.S. has also ordered 300 million doses, though the Food and Drug Administration has not yet given it emergency use authorization. AstraZeneca said Monday it will submit the full results of its U.S. trial to the FDA and for peer review to be published in a journal.