Evidence continues to build for long-lasting immunity to Covid-19 following disease infection, with the publication of a new study showing a durable immune response as far as eight months after the initial onset of symptoms.

AstraZeneca is likely to run an additional global trial to assess the efficacy of the company’s Covid-19 vaccine using a lower dosage, the British drugmaker’s chief executive was quoted as saying amid questions over the results of a late-stage study.