AstraZeneca Vaccine Shows 70% Efficacy in Early Trial Data
AstraZeneca reports its COVID-19 vaccine demonstrates an average 70.4% effectiveness, presenting a perplexing discrepancy between dosing regimens that researchers are still working to understand.
AstraZeneca announces that its COVID-19 vaccine reduces the risk of symptomatic illness by an average of 70.4% based on an interim analysis of Phase 3 trials in the United Kingdom and Brazil. While this effectiveness falls short of the 95% efficacy rates recently reported by Moderna and Pfizer-BioNTech, University of Oxford researchers still hail the data as a promising step toward ending the pandemic.
The trial results reveal a perplexing discrepancy regarding the dosing schedule. Participants who receive two full doses show a 62% effectiveness rate, while a smaller subgroup of 2,741 participants who receive a half dose followed by a full dose achieves a 90% effectiveness rate.
AstraZeneca plans to discuss adding the half dose-full dose regimen to its ongoing trials with regulatory agencies. Experts like Anthony Fauci note that it remains unclear why the lower initial dose produces a better immune response, suggesting that further investigation is necessary to explain these surprising clinical findings.