A test tube labelled vaccine is seen in front of AstraZeneca logo in this illustration taken, September 9, 2020.Dado Ruvic | ReutersAstraZeneca shares fell Wednesday after a Brazilian health authority said a volunteer in its coronavirus vaccine study died.The Federal University of Sao Paulo, which is helping coordinate late-stage trials in Brazil, separately said that the volunteer was Brazilian, according to Reuters. Shares of AstraZeneca, a front-runner in the Covid-19 vaccine race, fell about 1% in early afternoon trading.The news comes as the Food and Drug Administration still has a late-stage clinical trial from AstraZeneca on hold in the United States. That means the company is unable to administer second doses of its two-dose vaccine regimen to U.S. participants.The company announced on Sept. 8 that its trial had been put on hold due to an unexplained illness in a patient in the United Kingdom. The patient is believed to have developed inflammation of the spinal cord, known as transverse myelitis. The trial has since resumed in the U.K. and other countries but is still on hold in the U.S.This is breaking news. Please check back for updates.