American pharmaceutical giant Johnson & Johnson on Monday, 12 October 2020, said it has hit pause on its much anticipated COVID-19 vaccine trial. This temporary halt is the result of unexplained illness in one of the study participants. This pause means that the online enrollment for phase 3 of the study, which began late September, has been closed for now. An independent patient safety committee is also being convened. (Read more: How are vaccines made?)

J&J’s phase 3 vaccine trial, dubbed ENSEMBLE, is a randomized, placebo-controlled study, the purpose of which is to evaluate the safety and efficacy of a single vaccine dose versus placebo in close to 60,000 adults, including many over 60 years of age. The trial also includes people with comorbidities who are more likely to develop severe COVID-19 if they contract the infection. According to a J&J press release, it had hoped to enrol participants from Argentina, Brazil, Chile, Colombia, Mexico, Peru, South Africa and the United States, before it hit this snag.

"Adverse events—illnesses, accidents, etc.—even those that are serious, are an expected part of any clinical study, especially large studies," said the company in a statement.

The COVID-19 shot is being developed by Janssen, an arm of Johnson & Johnson.

"Based on our strong commitment to safety, all clinical studies conducted by the Janssen Pharmaceutical Companies of Johnson & Johnson have prespecified guidelines. These ensure our studies may be paused if an unexpected serious adverse event (SAE) that might be related to a vaccine or study drug is reported, so there can be a careful review of all of the medical information before deciding whether to restart the study," the company said.

Last month, a large trial of another COVID-19 vaccine—by Oxford University and AstraZeneca—was put on hold due to a suspected adverse reaction in one of the patients in the United Kingdom. The Oxford trial, which was temporarily halted on 8 September 2020, was resumed after a week (as of 14 September 2020).

Medicines / Products that contain Johnson & Johnson hits pause on phase 3 trial of COVID-19 vaccine

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