AstraZeneca/Oxford COVID-19 Vaccine Achieves Good Safety, Efficacy in U.S. Trial

University of Oxford and AstraZeneca vaccine
University of Oxford and AstraZeneca vaccine [University of Oxford]

AstraZeneca has released results from a large Phase III study carried out in the U.S., Chile, and Peru, showing good efficacy and safety for its non-replicating adenoviral vector vaccine targeting SARS-CoV-2.

This vaccine (AZD1222) is not currently approved in the U.S., but has been approved and rolled out in many countries in Europe and in the U.K. where it was first developed as a collaboration between the University of Oxford and its spin-out company, Vaccitech, before AstraZeneca joined the collaboration.

There has been some controversy regarding the AstraZeneca/Oxford vaccine in Europe in recent months with criticism from some quarters about a lack of data in over 65s and more recently there were claims it might increase the risk of blood clots.

The data from the current trial should go some way to relieving anxieties about these claims. The researchers found the vaccine was 79% effective at preventing symptomatic COVID-19 and 100% effective at preventing severe disease or hospitalization in the whole cohort. It was also 80% effective at preventing symptomatic disease in over 65s who made up 20% of the participants.

“These findings reconfirm previous results observed in AZD1222 trials across all adult populations but it’s exciting to see similar efficacy results in people over 65 for the first time,” said Ann Falsey, M.D., a professor at the University of Rochester School of Medicine, and co-lead Principal Investigator for the trial.

Overall, the vaccine was well tolerated with no major safety concerns raised by the trial. The investigators specifically looked at whether the vaccine could increase the risk of blood clots and an independent data safety monitoring board found no increased risk of such clots or related events in the participants who received the vaccine.

The trial was large, with 32,449 participants. In addition to including a significant number of those over the age of 65 years, around 60% had comorbidities putting them at greater risk of severe COVID-19 such as diabetes, obesity or cardiovascular disease.

Participants were randomly assigned to vaccine—two doses with a four-week interval—or placebo in a 2:1 ratio, with approximately 21,583 participants receiving the vaccine. Overall, 141 symptomatic cases of COVID-19 occurred during the trial.

The positive results achieved in this trial are higher than those in the original trials of this vaccine. “This analysis validates the AstraZeneca COVID-19 vaccine as a much-needed additional vaccination option, offering confidence that adults of all ages can benefit from protection against the virus,” says Falsey.

The company now plans to submit this Phase III vaccine data to the FDA in an application for emergency approval. If approved it would add to the current vaccine options in the U.S. of the two-dose BioNTech/Pfizer and Moderna mRNA vaccines and the Johnson & Johnson one-dose non-replicating adenoviral vector vaccine.

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