It began in January as a “little lab project” after a curious new disease emerged in China. Little more than four months later, the eyes of the nation - and perhaps the world - are firmly upon Professor Adrian Hill and his team at Oxford University. This week, the pharmaceutical giant AstraZeneca announced a $1.2 billion deal with the US government to produce 400 million doses of the unproven coronavirus vaccine first produced in Prof Hill's Oxford lab. Meanwhile, the British Government has agreed to pay for up to 100 million doses, adding that 30 million may be ready for UK citizens by September. The stakes could hardly be higher. If proven effective, the ZD1222 vaccine would allow people to leave their homes, go back to work, and rebuild the economy. But Professor Hill, director of the university’s Jenner Institute, revealed that his team now faces a major problem, throwing the September deadline into doubt. In short, their adversary is disappearing so rapidly in the UK that the next phase of trials has only a 50 per cent chance of success. Without Covid-19 spreading in the community, volunteers will not catch the disease, leaving scientists unable to prove that their vaccine makes any difference. Professor Hill said that of 10,000 people recruited to test the vaccine in the coming weeks - half of whom will be given a placebo - he expected fewer than 50 people to catch the virus. If fewer than 20 test positive, then the results may be useless, he warned.