Johnson & Johnson voluntarily paused the clinical trial for its COVID-19 vaccine candidate Oct. 12 after learning of a participant's unexplained illness, STAT reported.
The study's online enrollment system has been closed, and the data and safety monitoring board is being called on, according to a document sent to outside researchers running the trial that was obtained by STAT.
The drugmaker told STAT that the study has been paused due to "an unexplained illness in a study participant," but declined to disclose further information.
"We must respect this participant's privacy," Johnson & Johnson told STAT. "We're also learning more about this participant's illness, and it's important to have all the facts before we share additional information."
Johnson & Johnson began enrolling participants in its phase 3 vaccine trial Sept. 23, aiming to gather 60,000 participants in the U.S., Mexico, Argentina, Brazil, Chile, Colombia, Peru and South Africa.
The drugmaker's single-shot vaccine candidate is the fourth to enter phase 3 testing in the U.S. Moderna's candidate and the one Pfizer is developing with BioNTech both entered phase 3 testing in July. The vaccine AstraZeneca is developing with the University of Oxford began phase 3 testing in August, but its U.S. trial is currently paused as its safety is reviewed following an adverse reaction in a U.K. trial participant.