Johnson & Johnson has paused all clinical trials of its experimental COVID-19 vaccine after a study participant had an unexplained illness. According to the company, it has temporarily paused further dosing in all of its COVID-19 vaccine candidate clinical trials, including a Phase III trial that began in September, while it investigates the illness.

Study pauses are not uncommon in clinical trials and are often resolved.

The Phase III ENSEMBLE trial of its Janssen COVID-19 vaccine candidate JNJ-78436735 involves an anticipated 60,000 adults in multiple countries, testing the safety and efficacy of a single dose versus a placebo in preventing COVID-19. A two-dose regimen is being tested in a separate trial.