Johnson & Johnson said Wednesday it has begun its phase three trial testing its potential coronavirus vaccine. J&J is the fourth drugmaker backed by the Trump administration's Covid-19 vaccine program Operation Warp Speed to enter late-stage testing. The others are Moderna, Pfizer and AstraZeneca. The trial will enroll up to 60,000 adult volunteers across 215 locations in the U.S. and other countries, according to the National Institute of Allergy and Infectious Diseases. Participants will be randomly selected to receive a dose of the potential vaccine or a placebo, according to details of the trial, which will determine whether the vaccine is safe and effective.
