AstraZeneca (NYSE:AZN) shares were lower Tuesday after the company said its late-stage trial for a potential coronavirus vaccine had been put on hold due to safety concerns.
Shares of the drugmaker were down nearly 2% ahead of the opening bell Wednesday.
“This is a routine action which has to happen whenever there is a potentially unexplained illness in one of the trials, while it is investigated, ensuring we maintain the integrity of the trials. In large trials illnesses will happen by chance but must be independently reviewed to check this carefully,” the company said
A person familiar with the development said researchers were told the hold was placed on the trial out of “an abundance of caution” after a suspected serious adverse reaction in a participant in the United Kingdom.
It’s unclear how long the hold on the trial will last. AstraZeneca began its trial late last month and is one of three companies currently in late-stage testing for a potential vaccine. The other two are Pfizer (NYSE:PFE) and Moderna (NASDAQ:MRNA), which both began their trials in late July.
The U.S. government announced May 21 that it would pay AstraZeneca up to $1.2 billion for its experimental vaccine developed alongside researchers at the University of Oxford. The U.S. will receive at least 300 million doses of the vaccine as part of its investment.
AstraZeneca’s vaccine, called AZD1222, uses genetic material from the coronavirus with a modified adenovirus. It uses technologies that were used to make an experimental Ebola vaccine, which was provided to people in the Democratic Republic of Congo in late 2019.
AstraZeneca shares dove $1.25, or 2.3%, to $53.46.