AstraZeneca Plc has begun a large-scale human trial of its coronavirus vaccine in the U.S., the company said in a statement, with plans to enroll as many as 30,000 adults to test the shot, Fortune reports.

The AstraZeneca shot, invented by researchers at the University of Oxford, is one of the farthest along of numerous Covid-19 vaccines in development. In addition to the U.S. trial, a final-stage test of the inoculation is underway in the U.K. and could yield preliminary results as soon as next month. Other companies that have Covid-19 vaccines in phase 3 trials include Moderna Inc. and Pfizer Inc.

The trial had been delayed for several days, according to researchers from the University of Wisconsin School of Medicine and Public Health who are helping conduct the tests. The university is one of the sites where the trial is being run, and plans to begin injecting healthy volunteers on Tuesday, September 1, according to William Hartman, a UW Health anesthesiologist and investigator on the trial. It plans to ramp up to injecting 50 people a day shortly after the September 7 Labor Day holiday, he said in an interview.

An August 27 article in the Palm Beach Post reported that the U.S. trial of AstraZeneca vaccine has been put on hold due to political pressure, perhaps because U.S. regulators planned to grant an emergency use authorization on the basis of the trial in Europe.