Once again, a coronavirus vaccine trial has been temporarily halted due to an unexplained illness in one of the study participants. This time, it's Johnson & Johnson's trial that's on pause; the company says in a statement that clinical studies are expected to have adverse events, but that this ailment will be "reviewed and evaluated by the ENSEMBLE independent Data Safety Monitoring Board (DSMB) as well as our internal clinical and safety physicians" before the company decides whether to restart the trial. A source tells Stat that such an event is not unexpected: "If we do a study of 60,000 people, that is a small village. In a small village there are a lot of medical events that happen."
The statement echoes that: "SAEs [Serious Adverse Events] are not uncommon in clinical trials, and the number of SAEs can reasonably be expected to increase in trials involving large numbers of participants," it notes. "Further, as many trials are placebo-controlled, it is not always immediately apparent whether a participant received a study treatment or a placebo." As Bloomberg reports, the last trial that was paused involved an AstraZeneca vaccine; while that study has since resumed in a number of countries, it is still on hold in the US. (Read more coronavirus vaccine stories.)