Studies of the final phases of AstraZeneca’s candidate vaccine for Covid-19 are temporarily suspended while the company investigates whether a patient suffered a serious side effect or if their discomfort is not linked to the inoculation.
In a statement issued Tuesday night, the company said its “standard review process created a pause in vaccinations to allow review of safety data.”
AstraZeneca did not disclose any information about the possible side effect, other than calling it “a potentially unexplained illness.” The STAT news portal was the first to report the pause in testing, claiming that the possible side effect occurred in the UK.
A spokesperson for AstraZeneca confirmed that the pause in vaccinations covers studies in the United States and other countries. Late last month, AstraZeneca began recruiting 30,000 people in the United States for its largest trial of the vaccine. It is also testing the vaccine, developed by the University of Oxford, in thousands of people in Britain, and in smaller-scale studies in Brazil and South Africa.
Two other vaccines are in the final stages of testing in the United States: one produced by Moderna Inc. and the other by Pfizer and the German laboratory BioNTech. Those two vaccines work differently than AstraZeneca’s, and the studies have already recruited two-thirds of the volunteers in need.
Temporary pauses in large-scale medical studies are not unusual, and investigating any possible serious side effects or unexpected reactions is mandatory. AstraZeneca noted that the problem could be a coincidence; Diseases of all kinds can arise in studies of thousands of people.
“We are working to expedite the review of that lone event to minimize any potential impact on the testing schedule,” the company said in its statement.
The announcement came on the same day that AstraZeneca and eight other pharmaceutical companies pledged to uphold the highest ethical and scientific standards in the development of their vaccines.
That came amid fears that President Donald Trump will pressure the Food and Drug Administration (FDA) to approve a vaccine before it is shown to be safe and effective.
The United States has invested billions of dollars to rapidly develop a coronavirus vaccine. But public fears that a vaccine will be ineffective and unsafe could prove disastrous, and derail efforts to vaccinate millions of Americans.
Representatives for the FDA did not immediately respond to requests for comment.