ALISTAIR SMOUT  THE University of Oxford's possible COVID-19 vaccine could be rolled out by the end of the year but there is no certainty, the lead developer of the vaccine has announced. The experimental vaccine, which has been licensed to AstraZeneca, produced an immune response in early-stage clinical trials, data showed on Monday, preserving hopes it could be in use by the end of 2020. "The end of the year target for getting vaccine roll-out, it's a possibility but there's absolutely no certainty about that because we need three things to happen," Sarah Gilbert told BBC Radio. She said it…