(Reuters) – Johnson & Johnson JNJ.N has suspended clinical trials of its coronavirus vaccine candidate due to unexplained illness in a study participant, delaying one of the most important efforts to contain the global pandemic.
The move comes about a month after AstraZeneca AZN.L has also suspended trials of its experimental coronavirus vaccine – which uses similar technology – due to a participant falling ill.
J&J said Monday the disease was under review by an independent data and safety oversight committee as well as the U.S. group’s clinical and safety doctors.
The company, which releases its quarterly financial results Tuesday morning, said such pauses were normal in large lawsuits, which can include tens of thousands of people.
He added that the voluntary “study break” in administering doses of the candidate vaccine was different from a “regulatory suspension” imposed by health authorities.
AstraZeneca last month suspended late-stage trials of its experimental coronavirus vaccine developed with the University of Oxford due to an unexplained illness in a participant in a British study.
While AstraZeneca’s trials in Britain, Brazil, South Africa and India have since resumed, its trial in the United States is still pending, awaiting regulatory review.
The J&J and AstraZeneca vaccines are both based on a so-called adenovirus, a harmless modified virus that instructs human cells to produce vaccine proteins.
They are both also part of the US government’s Operation Warp Speed program to support vaccine development.
“This could be a second case of adenoviral vaccine to raise safety concerns,” said Olga Smolentseva, analyst at Bryan Garnier.
AstraZeneca and medical experts say trial suspensions to investigate the cause of a participant’s illness are not uncommon. Underwriters of clinical trials insurance said premiums for coronavirus vaccine studies were only slightly higher than for pre-pandemic vaccines.
On September 22, J&J became the fourth Warp-Speed participant to enter the final phase of human testing, with the goal of recruiting 60,000 volunteers in the United States and abroad. “Everyone is on high alert because of what happened with AstraZeneca,” Dr William Schaffner, professor of infectious diseases at Vanderbilt University School of Medicine, said via email, adding that the information gathering could take a week.
“It’s probably a neurological event,” he said. Last month, J&J said its vaccine candidate produced a strong immune response in an early to mid-stage clinical trial. This prompted the company to launch the trial on a large scale, with results expected by the end of this year or early 2021.
J&J declined to give further details on the illness due to confidentiality concerns. He said some study participants were given placebos and it was not always clear whether someone with a serious adverse event in a trial was receiving a placebo or the treatment.
Stat News reported the break here earlier, citing a document sent to external researchers, which said that a ‘pause rule’ had been followed, the online system used to enroll patients in the study had been closed and the Data and Security Oversight Committee would be convened.