Johnson & Johnson (J&J) has paused a phase 3 study of its investigational COVID-19 vaccine after a participant in the trial developed an unexplained illness.
According to a document sent to outside researchers, seen by STAT News, the online system used to enrol patients has been closed after a ‘pausing rule’ was imposed.
J&J added that the independent data and safety monitoring board (DSMB) and J&J’s own clinical and safety physicians are reviewing the participant’s illness.
In a statement, J&J confirmed that it had paused the trial due to an “unexplained illness in a study participant”. The company offered no further details regarding the nature of the adverse event and added that the vaccine study is not currently under a clinical hold.
“We must respect this participant’s privacy. We’re also learning more about this participant’s illness, and it’s important to have all the facts before we share additional information,” J&J added.
J&J initiated the phase 3 trial in September and plans to enrol up to 60,000 volunteers across three continents. It is testing the safety and efficacy of a single dose of the COVID-19 vaccine, JNJ-78436735/Ad26.COV2.S, versus placebo in preventing COVID-19.
The investigational candidate uses J&J’s AdVac technology platform, which was also used to develop and manufacture the company’s exiting Ebola vaccine as well as its other investigational vaccines for Zika, RSV and HIV.
J&J is the second company with a COVID-19 vaccine in development that has had to pause its study after a participant in its phase 3 study developed an illness.
At the beginning of September, AstraZeneca (AZ) put all clinical trials of its COVID-19 vaccine on hold after a patient fell ill. The illness that the AZ participant reportedly experienced was transverse myelitis, an inflammation of the spinal cord.
Although trials have resumed in the UK and other trial sites across the globe, the US AZ study remains on hold.
In an interim analysis of results from J&J’s ENSEMBLE phase 1/2a trial, the vaccine demonstrated a promising safety profile and immunogenicity after one dose.
J&J maintained that safety events such as the unexplained illness are expected in wide-scale efficacy studies, given the fact that the vaccine is being tested in a much larger patient population.