A participant in the trials of a Covid-19 vaccine being developed by AstraZeneca and Oxford University has died. Seems like kind of a big deal. But the authorities have assured us that, after a "thorough" review, there's nothing to worry about and the trials are proceding. AstraZeneca said in a statement that it could not comment on individual cases but it "can confirm that all required review processes have been followed... These assessments have not led to any concerns about continuation...