Your questions on Moderna, second doses, AstraZeneca and blood clots answered in our Covid vaccine Q&A Save Paul Nuki, Global Health Security Editor, London Follow The under 30s are to be offered an alternative to the AstraZeneca vaccine, it was announced yesterday, after the UK's medicines regulator found that the vaccine was linked to blood clots in young people. The benefits of the AstraZeneca vaccine continue to outweigh any risks for most people, the UK medicines watchdog said, as European regulators ruled that unusual blood clots were "very rare side effects" of the jab. Scientists have also insisted that further research is needed to understand more about the risk of these rare blood clots.