1,700 person study, 90% of people created antibodies after one dose, the others did after two doses.
They still don't know how long the antibodies will last or just how protective it may be. Side effects so far have been fever and headache.
"The trial has also been expanded to other countries because levels of coronavirus are low in the UK, making it hard to know if the vaccine is effective.
There will be a large trial involving 30,000 people in the US as well 2,000 in South Africa and 5,000 in Brazil.
There are also calls to perform "challenge trials" in which vaccinated people are deliberately infected with coronavirus. However, there are ethical concerns due to a lack of treatments."
