WASHINGTON: Johnson & Johnson said Monday it had temporarily halted its Covid-19 vaccine trial because one of its participants had become sick.

"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," the company said in a statement.

The pause means the enrollment system has been closed for the 60,000-patient clinical trial while the independent patient safety committee is convened.

J&J said that serious adverse events (SAEs), such as accidents or illnesses, are "an expected part of any clinical study, especially large studies." Company guidelines allow them to pause a study to determine if the SAE was related to the drug in question and whether to resume study.

The J&J Phase 3 trial had started recruiting participants in late September, with a goal of enrolling up to 60,000 volunteers across more than 200 sites in the US and around the world, the company and the US National Institutes for Health (NIH), which is providing funding, said.

The other countries where the trials were taking place are Argentina, Brazil, Chile, Colombia, Mexico, Peru and South Africa.

With the move, J&J became the tenth maker globally to conduct a Phase 3 trial against Covid-19, and the fourth in the US. The US has given J&J about $1.45 billion in funding under Operation Warp Speed.