A spokesperson for AstraZeneca said the company’s “standard review process triggered a pause to vaccination to allow review of safety data”. It is unclear who had placed a temporary halt to the trial and how long the hold will last.
The spokesperson described the pause in as “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”.
They added the company is “working to expedite the review of the single event to minimise any potential impact on the trial timeline”.
AstraZeneca said in a statement: “As part of the ongoing, randomised, controlled global trials of the Oxford coronavirus vaccine, our standard review process triggered a pause of vaccination to allow review of safety data.
“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.
“We are working to expedite the review of the single event to minimise any potential impact on the trial timeline.
“We are committed to the safety of our participants and the highest standards of conduct in our trials.”
AstraZeneca’s shares dropped more than 6 percent in after-hours trading Tuesday following the news.
The firm began its trial late last month and is one of three developers currently in late-stage testing for a potential vaccine.
The other two firms, industry giants Pfizer and Moderna began their trials in late July.
AstraZeneca’s early-stage trials in July seemed encouraging after the firm published favourable data.
At the time, the company reported no serious adverse effects.
However, some mild-symptoms including fatigue and headache had been noted.
Other side-effects were reported such as soreness where the injection was administered, muscle ache, chills and fever.
The company is currently in mitigation status in order to complete the trials as close as possible to its original end date.
AstraZeneca’s trials had reached phase 3, the final stage before safety and efficacy reports can be sent to regulators for authorisation.
The trials were being carried out at dozens of facilities across the US and worldwide.