A large trial in the US and two South American countries of the Oxford-AstraZeneca vaccine has shown a 79 percent efficacy rate at preventing symptomatic COVID-19 and 100 percent effectiveness in stopping severe disease and hospitalization, the biotech firm said on Monday.

A Phase III study of the vaccine, developed by Oxford University and produced by AstraZeneca was conducted by AstraZeneca plc in the US, Chile, and Peru and reaffirmed that the vaccine is "safe and highly effective", adding to previous trial data from the UK, Brazil, and South Africa.

The Oxford/AstraZeneca vaccine is also being produced as part of a tie-up by the Serum Institute of India. The vaccine's efficacy was consistent across ethnicity and age, and in participants aged 65 years and over, its effectiveness was 80 percent.

"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," said Andrew Pollard, Professor of Paediatric Infection and Immunity and Lead Investigator of the Oxford University trial of the vaccine.

"We can expect strong impact against COVID-19 across all ages and for people of all different backgrounds from the widespread use of the vaccine," he said.

In the trial, which recruited over 32,000 volunteers across all age groups, the participants received either two standard doses of the Oxford-AstraZeneca vaccine or a placebo vaccine, at a four-week interval. The vaccine was found to be well-tolerated, and the independent Data Safety Monitoring Board (DSMB) identified no safety concerns related to the vaccine.

AstraZeneca said that it continues to engage with governments, multilateral organizations, and collaborators around the world to ensure broad and equitable access to the vaccine at no profit for the duration of the coronavirus pandemic.

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