Where Things Stand in the Race for a Covid-19 Vaccine

Thousands of researchers in more than 30 countries have been collaborating and competing this year on about 200 projects to develop a vaccine against the novel coronavirus in record time. In the most encouraging scientific advance so far, the vaccine being developed by Pfizer Inc. and BioNTech SE prevented more than 90% of symptomatic infections in a study of tens of thousands of volunteers. However, earlier decisions by AstraZeneca Plc and Johnson & Johnson to pause testing on their promisi