NPR News

AstraZeneca Vaccine Can Prevent COVID-19, Phase III Study Says

By Jaclyn Diaz

Published March 22, 2021 at 11:12 AM EDT

Results from a Phase III trial show the Oxford AstraZeneca COVID-19 vaccine can be 79% effective at preventing symptoms of COVID-19. [Finnbarr Webster / Getty Images] — Results from a Phase III trial show the Oxford AstraZeneca COVID-19 vaccine can be 79% effective at preventing symptoms of COVID-19.

Preliminary results from a study examining the efficacy of the Oxford-AstraZeneca coronavirus vaccine indicate it is significantly effective at preventing severe illness from COVID-19.

Results of the trial, which involved more than 32,000 volunteers, showed two doses of the vaccine administered four weeks apart had an efficacy of 79% at preventing symptoms of COVID-19. In participants aged 65 years and over, vaccine efficacy could be as high as 80%, AstraZeneca announced early Monday. It had an efficacy of 100% at preventing severe disease and hospitalization.

The results may mean the doses could soon be put into the arms of Americans. Data pulled from the study provides data to the Food and Drug Administration needed to grant the AstraZeneca vaccine an emergency use authorization. This approval would allow use of the vaccine by the general public to combat the coronavirus pandemic.

AstraZeneca's vaccine can be stored, transported and handled at normal refrigerated conditions (2-8 degrees Celsius or 36-46 degrees Fahrenheit) for at least six months. The company said it can also be administered without the need for preparation within existing healthcare settings.

The U.S. already has Pfizer, Moderna and Johnson & Johnson coronavirus vaccines distributed to the general public. But the Pfizer and Moderna vaccines must be stored at extremely cold temperatures, making shipping, storage and distribution difficult.

The Centers for Disease Control and Prevention report that as of Sunday 156,734,555 total vaccine doses have been distributed in the U.S. The agency reports 124,481,412 vaccine doses have been administered.

The vaccine is already being used around the world to prevent COVID-19. In recent weeks, several European countries temporarily suspended the use of the AstraZeneca vaccine following reports of blood clotting in at least 30 patients.

Most countries resumed using it, however, after the European Medicines Agency conducted an investigation and declared on Thursday that the AstraZeneca vaccine is safe and effective. The EMA said the benefits of the vaccine far outweigh the potential risks.