A late-stage study of Johnson & Johnson’s COVID-19 vaccine candidate has been paused while the company probes whether a study participant’s unexplained illness is related to the shot.

The New Brunswick-based company announced in a statement Monday evening that illnesses, accidents and other so-called adverse events are an expected part of large clinical studies.

VIRUS TRACKER: New York, New Jersey, Connecticut coronavirus cases and deaths 

MORE: New Jersey Coronavirus Dashboard 

In a statement, the company says, in part, "We have temporarily paused further dosing in all our COVID-19 vaccine candidate clinical trials, including the Phase 3 ENSEMBLE trial, due to an unexplained illness in a study participant. Following our guidelines, the participant's illness is being reviewed and evaluated by the ENSEMBLE independent Data Safety Monitoring Board, as well as our internal clinical and safety physicians."

Its physicians and a safety monitoring panel will try to determine what might have caused the illness. The company did not release details or symptoms of the person's illness, and only said that researchers are evaluating the subject to see if the illness is related to their medication.

Johnson & Johnson officials also emphasize that the person who got sick could have been taking the placebo. But they say that everything is on hold until more information can be gathered.

The company adds it must respect this participant's privacy and learn more about the illness, as well as gather all the facts before sharing additional information.

The pause is at least the second such hold to occur among several vaccines that have reached large-scale final tests in the U.S.

Final-stage testing of a vaccine made by AstraZeneca and Oxford University remains on hold in the U.S., though it has restarted elsewhere.

AP wire services helped contribute to this report.