Johnson & Johnson’s COVID-19 vaccine study has been paused due to an unexplained illness in a study participant, the company announced on Monday.
“We have temporarily paused further dosing in all our COVID-19 vaccine candidate clinical trials, including the Phase 3 ENSEMBLE trial, due to an unexplained illness in a study participant,” J&J said in a statement on its website.
“Following our guidelines, the participant’s illness is being reviewed and evaluated by the ENSEMBLE independent Data Safety Monitoring Board (DSMB) as well as our internal clinical and safety physicians.”
The company added that it is learning more about the participant’s illness, and that it is “important to have all the facts” before it shares additional information.
J&J said that its pre-specified guidelines for clinical studies ensure that if an unexpected serious adverse event occurs, “there can be a careful review of all of the medical information before deciding whether to restart the study.”
In its announcement, the company made a distinction between the use of the terms “study pause” and “regulatory hold,” with the former being initiated by the study sponsor and is a “standard component of a clinical trial protocol,” and the latter being a requirement by a regulatory health body, such as the U.S. Food and Drug Administration (FDA).
J&J said that it typically does not communicate study pauses publicly, but proactively discloses any regulatory hold of a “pivotal clinical trial.”
Johnson & Johnson declined to elaborate about the illness due to privacy concerns, Reuters reported. It did say that some participants in studies get placebos, and it was not always clear whether a person suffering a serious adverse event in a clinical trial received a placebo or the treatment.
The phase three trial marks the final step before drug manufacturers can seek emergency use authorization to widely distribute their vaccines. There is no authorized vaccine for COVID-19 yet.
J&J is pursuing a single-shot vaccine which is different from its three rival manufacturers that are testing vaccines that would require two shots separated by several weeks. Paul Stoffels, J&J’s chief scientific officer, said at the time that the company is seeking “to deliver a vaccine for emergency use authorization in early 2021.”
Participants enrolled in the trial “will include those both with and without comorbidities associated with an increased risk for progression to severe COVID-19, and will aim to enroll participants in Argentina, Brazil, Chile, Colombia, Mexico, Peru, South Africa, and the United States,” the company said at the time. The participants would also include “significant representation from those that are over age 60.”
The clinical trial would be considered a success if it proves to be at least 60 percent effective, with a study protocol that could have an efficacy answer after 154 people became infected with the virus, the company said.