AstraZeneca Plc stopped giving shots of its experimental coronavirus vaccine after a person participating in one of the company’s studies got sick, a potential adverse reaction that could delay or derail efforts to speed an immunization against Covid-19.
The pause stemmed from a standard review of the company’s vaccine trials after one person developed an unexplained illness, AstraZeneca said in a statement. The move was intended to give researchers time to examine safety data while maintaining the integrity of the trials, the company said. The drugmaker’s shares fell as much as 3% in London Wednesday morning. Later, they pared the decline to 1.1% as investors took it in stride as a fairly common event during testing.
The vaccine, which AstraZeneca is developing with researchers from the University of Oxford, has been viewed as one of the leading candidates. The partners are aiming to enroll as many as 50,000 participants for late-stage trials that are underway in the U.K., the U.S., Brazil and South Africa, with others planned for Japan and Russia.
AstraZeneca has a market value of about $140 billion and the largest weighting of all the companies in the U.K.’s FTSE-100 Index.