Johnson & Johnson COVID-19 vaccine trial paused due to 'unexplained illness'

A Johnson & Johnson building in Irvine.
(Image credit: Getty Images)

Johnson & Johnson on Monday night announced that it has paused its COVID-19 vaccine trial due to one of the volunteers coming down with an "unexplained illness."

In a statement, Johnson & Johnson said that under its guidelines, the "participant's illness is being reviewed and evaluated" by the study's independent data safety monitoring board (DSMB), as well as internal clinical and safety physicians. The company also said that "adverse events — illnesses, accidents, etc. — even those that are serious, are an expected part of any clinical study, especially large studies."

Johnson & Johnson's vaccine arm, Janssen, began the Phase 3 clinical trial in September. There are 60,000 participants, and each person is receiving one dose of the vaccine. Advanced clinical trials are conducted so researchers can determine whether participants are experiencing side effects, and Johnson & Johnson said it is not revealing what illness the volunteer has due to privacy reasons.

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Dr. Ashish Jha, dean of the Brown University School of Public Health, told CNN that the pause is "completely expected" due to how large the study is, and this is "just a reminder how ridiculous it is to try and meet a political timeline of having a vaccine before Nov. 3." Jha added that it is important for the vaccine to be "safe and we've got to let the process play out and it's going to take a while. To me, it's reassuring that companies are acting responsibly and pausing when they need to."

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Catherine Garcia

Catherine Garcia is night editor for Her writing and reporting has appeared in Entertainment Weekly and, The New York Times, The Book of Jezebel, and other publications. A Southern California native, Catherine is a graduate of the University of Redlands and the Columbia University Graduate School of Journalism.