The interim analysis of AZD1222 is based on 32,449 participants accruing 141 symptomatic cases of COVID-19 across 88 sites in the U.S., Chile, and Peru. In the study, one participant received a placebo for every two participants who received AZD1222, resulting in approximately 20,000 people receiving the investigational vaccine.

The vaccine was administered as two doses four weeks apart. The results from the analysis were consistent across ethnicity and age, with a vaccine efficacy of 80% in participants ages 65 years and older.

The vaccine was well tolerated with no related safety concerns, according to the independent data safety monitoring board. The board found no increased risk of thrombosis or events characterized by thrombosis among the 21,583 participants receiving at least one dose of the vaccine.

AstraZeneca will continue to analyze the data and prepare for the primary analysis to be submitted to the U.S. Food and Drug Administration (FDA) for emergency use authorization (EUA) in the coming weeks. In parallel, the primary analysis will be submitted for publication in a peer-reviewed journal.

The vaccine can be stored, transported, and handled at normal refrigerated conditions for at least six months, according to the company.

The phase III trial was funded by the Biomedical Advanced Development Authority (BARDA) and the U.S. National Institute of Allergy and Infectious Diseases (NIAID).