Half the UK population has now had at least one jab against Covid-19 and Public Health England says the vaccines have already saved at least 6,000 lives and stopped many becoming ill. But for all its success, the rollout has raised questions about rare but serious side-effects. The one that’s caught the public eye is the very slight risk of blood clots from the AstraZeneca vaccine. Even though there’s no proof the jab is to blame, the Medicines and Healthcare products Regulatory Agency (MHRA) has recommended that adults under 30 are offered one of the other vaccines available, to be on the safe side.