AstraZeneca said that it had paused research on its experimental coronavirus vaccine after a person who was taking part in a clinical trial became ill.The vaccine, which AstraZeneca is developing with researchers from the University of Oxford, has been viewed as one of the leading candidates to reach the market.The decision to tap the brakes jolted investors, sending AstraZeneca’s US-traded shares down sharply, while boosting the stocks of some rivals developing different potential Covid-19…