The EU is accusing pharmaceutical companies of prioritising vaccine supplies to the UK.
The project has started Phase III of the human trials to assess how the vaccine works in a large number of people over the age of 18.
A low-cost, widely used anti-inflammatory drug improved survival in patients with Covid-19, the first treatment to show life-saving promise months into the pandemic.
Professor Peter Horby, Professor of Emerging Infectious Diseases and Global Health, has said that dexamethasone is the 'only drug shown to reduce mortality'.
Around 90% of experimental vaccines never reach the clinic because of problems in development or manufacture.