The AstraZeneca vaccine trial, on hold in the United States since early September, also got the greenlight Friday to restart from the Food and Drug Administration, according to a company statement.
When a potential adverse event occurs during a clinical trial, the testing is typically stopped so that an independent data and safety monitoring board can thoroughly investigate and determine whether the problem was likely related to the vaccine. Rules around clinical trials and patient privacy usually restrict details from being released, but the tremendous scrutiny of the coronavirus vaccine trials has led many experts to call for greater transparency in disclosing and explaining the reasons for such halts.
In the Johnson & Johnson trial, which was paused on Oct. 12, a man who received a vaccination suffered a stroke that may have been triggered by an infection. To conclude it was not likely to be related to the shot, investigators probed not only the medical details of the event, but also examined a safety database of 100,000 people who have received vaccines that use the same underlying technology.
The investigation found “no clear cause" of the incident, according to a company statement. It also found no evidence the vaccine triggered the event, the details of which were not disclosed by the company. The independent board that monitors the trial recommended lifting the pause.
“With the information which we gathered to date and the information from external experts, the company found no evidence the vaccine candidate caused it,” Paul Stoffels, chief scientific officer of Johnson & Johnson said in an interview. He did not offer any details of the illness, citing patient privacy.
The company is testing the only vaccine that aims to protect people with a single shot; other prospective vaccines require a return visit and second shot three to four weeks after the first to trigger a protective immune response.
It was the second late-stage vaccine trial put on hold in recent weeks; the vaccine being developed by AstraZeneca and the University of Oxford was halted on Sept. 6 after a British participant developed a neurological problem. While the AstraZeneca study had resumed in the rest of the world, its clearance to restart in the U.S. came Friday and was first reported by the Wall Street Journal.
AstraZeneca spokeswoman Michele Meixell did not provide further information on the illness, but said the FDA reviewed data from the trials running around the world before concluding it was safe to restart. She said the company was adding a new expert panel “to provide advice on diagnosis and causality assessment of neurological events,”in addition to continuing standard company oversight and the independent data and safety committee.
Pausing and unpausing clinical trials happens routinely, and experts have said that the public should be confident the process worked as intended to protect the health and safety of participants.
“We see this all the time during clinical research," said Carlos del Rio, an infectious diseases physician at Emory University School of Medicine. "As long as the data and safety monitoring board has reviewed the data and says its OK to proceed, we proceed.”
But whether the temporary halts -- particularly the prolonged pause of the AstraZeneca trial -- dampens volunteers’ interest in participating remains to be seen.
“We are excited to get this trial back up and running,” said William Hartman, a principal investigator of the AstraZeneca trial at the University of Wisconsin Hospital and Clinics. “It is too soon to tell whether participant enthusiasm will approach what it was prior to the pause. We certainly hope it will.”