AstraZeneca has reported that the Phase III trial of its AZD1222 vaccine in the US showed statistically significant efficacy of 79% at preventing symptomatic Covid-19 and 100% efficacy at preventing severe disease and hospitalisation.

Co-invented by the University of Oxford and its spin-out company Vaccitech, the vaccine uses a replication-deficient chimpanzee viral vector based on adenovirus and has the genetic material of the SARS-CoV-2 virus spike protein.

Named D8110C00001, the trial was led by AstraZeneca and funded by the US Biomedical Advanced Research and Development Authority (BARDA).

The randomised, double-blind, placebo-controlled multi-centre study analysed the safety, efficacy, and immunogenicity of AZD1222 versus placebo in preventing Covid-19, in 32,449 subjects across 88 trial centres in the US, Peru and Chile.

The trial subjects were aged 18 years and above who are healthy or have medically stable chronic diseases and at increased risk of Covid-19 exposure.

They were randomised in a 2:1 ratio to receive two intramuscular doses of either 5×1010 viral particles of AZD1222 or saline placebo four weeks apart.

This interim safety and efficacy analysis was conducted on accruing 141 symptomatic Covid-19 cases.

The vaccine was well-tolerated, and no vaccine-related safety concerns related were reported by the independent data safety monitoring board (DSMB).

Furthermore, the DSMB found no enhanced risk of thrombosis or events characterised by thrombosis among the 21,583 subjects who were given at least one vaccine dose.

AstraZeneca BioPharmaceuticals R&D executive vice-president Mene Pangalos said: “These results add to the growing body of evidence that shows this vaccine is well tolerated and highly effective against all severities of Covid-19 and across all age groups.

“We are preparing to submit these findings to the US Food and Drug Administration and for the rollout of millions of doses across America should the vaccine be granted US Emergency Use Authorisation.”