US trial results underscore efficacy and safety of Oxford/AstraZeneca COVID-19 vaccine

The Oxford/AstraZeneca COVID-19 vaccine was highly effective at preventing symptomatic disease and hospitalisation in the US phase III trial, including in participants aged 65 years and over.

Several EU countries recently paused rollout of the Oxford/AstraZeneca vaccine over blood clot concerns, despite reassurances from the European Medicines Agency and WHO. | GETTY IMAGES
Several EU countries recently paused rollout of the Oxford/AstraZeneca vaccine over blood clot concerns, despite reassurances from the European Medicines Agency and WHO. | GETTY IMAGES

The Oxford/AstraZeneca vaccine showed 79% efficacy at preventing symptomatic COVID-19 and 100% efficacy at preventing severe disease and hospitalisation, according to interim analysis of data from 32,449 participants in the US trial. 

Vaccine efficacy was consistent across ethnicity and age, with 80% efficacy in participants aged 65 years and over, who made up a fifth of the trial population.

The vaccine was well tolerated, with no reported safety concerns including no increased risk of thrombosis or thrombotic events. 

Validation

Ann Falsey, professor of medicine at the University of Rochester School of Medicine, US, and co-lead principal investigator for the trial, said: '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. 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.'

The randomised, double-blind, placebo-controlled trial took place in the US, Peru and Chile, with participants receiving two doses of the vaccine administered at a 4-week interval. Among those included in the interim analysis, approximately 79% were white, 8% black, 4% native American and 4% Asian. Overall 22% of participants were Hispanic.

Approximately 60% of participants had co-morbidities associated with an increased risk for progression of severe COVID-19, such as diabetes, severe obesity or cardiac disease.

Andrew Pollard, professor of paediatric infection and immunity, and lead investigator of the Oxford University trial of the vaccine, said: 'These results are great news as they show the remarkable efficacy of the vaccine in a new population and are consistent with the results from Oxford-led trials.'

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