A clinical trial of the Oxford vaccine, now manufactured by AstraZeneca, began in the United Kingdom last month. By Jon CohenScience’s COVID-19 reporting is supported by the Pulitzer Center.Operation Warp Speed, the Trump administration’s bid to deliver a COVID-19 vaccine faster than any previous vaccine, is both turning heads and raising eyebrows with a major new investment that promises to shave weeks off its already ambitious timeline.Warp Speed’s earlier target of mass immunizations of Americans starting in November already had many scientists and public health officials wondering whether the clinical trials needed to assure that a vaccine for the new coronavirus was safe and effective before wide-scale use could possibly be completed