Pharma major Johnson & Johnson has said its COVID-19 vaccine study has been temporarily halted due to an unexplained illness in a trial participant.
"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 injection is being developed by the Janssen vaccine arm of Johnson & Johnson.
The company has not yet revealed details about the unexplained illness but has stopped trials while doctors find out if the illness was caused due to the vaccine or was a coincidence.
The idea behind clinical trials is to explore the dangerous side effects of vaccination.
"Adverse events -- illnesses, accidents, etc. -- even those that are serious, are an expected part of any clinical study, especially large studies," the company added.
The company also claimed its strong commitment to safety.
All clinical trials carried out by the Janssen Pharmaceutical Company have prespecified guidelines that maintain that studies must be paused in case an unforeseen serious adverse event (SAE) is noticed in relation to the vaccine so there can be a careful review of all medical information, the company said.
"We must respect this participant's privacy. We're also learning more about this participant's illness, and it's important to have all the facts before we share additional information."
The drugmaker said, "Serious adverse events are not uncommon in clinical trials, and the number of serious adverse events can reasonably be expected to increase in trials involving large numbers of participants. Further, as many trials are placebo-controlled, it is not always immediately apparent whether a participant received a study treatment or a placebo."
The Dean of the Brown University School of Public Health Ashish Jha said that this pause is not immediately concerning.
"This is completely expected, and it's just a reminder how ridiculous it is to try and meet a political timeline of having a vaccine before November 3," Jha told CNN
"The Johnson & Johnson trial is the biggest trial of the vaccine that I know of -- 60,000 people," Jha said.
"Within that trial you'd expect a few pauses," he added.
However, the drugmaker claimed that there is a "significant distinction" between a study pause and a regulatory hold on a clinical trial.
It further said that a study pause, in which recruitment or dosing is paused by the study sponsor, is a standard component of a clinical trial protocol.
After AstraZeneca's vaccine trial, this is the second Phase Three vaccine trial to be paused in the United States.
However, AstraZeneca's trial has resumed in other countries but still remains paused in the United States while the US Food and Drug Administration investigates.
Jha further said that they want the vaccine to be safe.
"To me, it's reassuring that companies are acting responsibly and pausing when they need to," he said.
Phase Three trial of Johnson's vaccine started in September.
It's one of six coronavirus vaccines being tested in the US, and one of four in the most advanced stage.
It requires just one dose and hence, federal officials have said they hope testing may be completed a bit faster than other vaccines, including those being made by Moderna and Pfizer, which require two doses, CNN further reported.