AstraZeneca became the latest pharmaceutical company to unveil positive data in the global race for a coronavirus vaccine.
More than 23,000 adults are currently being assessed in the trials in the US, Japan, Russia, South Africa, Kenya and Latin America.
Oxford professor Andrew Pollard says their dosing regimens may be around 90 per cent effective and so more people could be vaccinated with a planned vaccine supply.
AstraZeneca say they are looking at producing three billion doses of the vaccine in 2021.