British-Swedish pharma firm AstraZeneca has temporarily put on hold phase-3 trials of its vaccine candidate after a volunteer reportedly suffered a serious adverse reaction in the UK.
The AZD1222 COVID-19 vaccine human clinical trial has been paused in the United States (US) and other countries, as confirmed by the company in a statement issued by the company on Tuesday.
However, the vaccine trials have been halted, not stopped, as the pharma company is going to conduct a "review of safety data by an independent committee", it stated in its email statement, adding that the (safety) assessment is a "routine action, which has to happen whenever there is a potentially unexplained illness in one of the trials, while it is investigated".
Meanwhile, AstraZeneca did not divulge any further details on the nature of the illness in the study participant, or when the (last stage) trial is expected to resume.
However, the volunteer is expected to recover, according to Stat News, which first reported the suspension due to a "suspected serious adverse reaction." Stat News is a US-based health-oriented news website.
Albeit, the company elucidated that it is expediting the "standard review process" in hopes that it will not cause any extreme delays.
But the suspension dims prospects for an early rollout amid reports that the US was aiming for a fast-track approval before the November presidential election.
The U.S. Food and Drug Administration defines an adverse event as one in which evidence suggests a possible relationship to the drug being tested.
According to a New York Times report, which cited a person familiar with the situation, a participant based in the UK was found to have transverse myelitis, an inflammatory syndrome that affects the spinal cord and is often sparked by viral infections.
Whether the illness was directly linked to AstraZeneca's vaccine remains unclear, the report said.
AstraZeneca's shares fell more than 8% in after-hours U.S. trading, while shares in rival vaccine developer Moderna Inc rose more than 4%. Shares in AstraZeneca's Indian unit, AstraZeneca Pharma India Ltd, tumbled more than 12%.
The vaccine, being jointly developed by the company with the University of Oxford, has been described by the World Health Organisation (WHO) as probably the world's leading candidate and the most advanced in terms of development.
The vaccine candidate is in late-stage clinical trials in the US, Britain, Brazil, and South Africa, and additional trials are planned in Japan and Russia. The trials aim to enrol up to 50,000 participants globally.
Meanwhile, South Korea said on Wednesday it would look into the suspension and review its plan to participate in the manufacturing of the vaccine.
"It's not rare that clinical trials get suspended as various factors interact," health ministry official Yoon Tae-ho told a briefing.
The decision to put the trial on hold has impacted clinical trials being conducted by other vaccine makers, which are looking for signs of similar reactions, Stat said.
Moderna said in an emailed statement that it was "not aware of any impact" on its ongoing COVID-19 vaccine study at this time.
Nine leading US and European vaccine developers pledged on Tuesday to uphold scientific safety and efficacy standards for their experimental vaccines despite the urgency to contain the coronavirus pandemic.
The companies, including AstraZeneca, Moderna, and Pfizer, issued what they called a "historic pledge" after a rise in concerns that safety standards might slip in the face of political pressure to rush out a vaccine.
The companies said they would "uphold the integrity of the scientific process as they work towards potential global regulatory filings and approvals of the first COVID-19 vaccines."
The other signatories were Johnson & Johnson, Merck & Co, GlaxoSmithKline, Novavax Inc, Sanofi, and BioNTech.