Johnson & Johnson Pauses COVID-19 Vaccine Clinical Trial

Johnson & Johnson recently announced that it paused dosing participants in the Phase 3 ENSEMBLE trial evaluating its COVID-19 vaccine after a study participant experienced an unexplained illness.

The company said that the participant’s illness is currently being reviewed and evaluated by the ENSEMBLE independent Data Safety Monitoring Board (DSMB), as well as clinical and safety physicians. It is unknown if the sick participant was taking the vaccine candidate or a placebo.

“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,” a Johnson & Johnson spokesperson said in the announcement. 

This announcement comes at the heels of Johnson & Johnson’s September 30th announcement that it found early positive results from the ongoing Phase 1/2a clinical trial of its vaccine candidate, Ad26.COV2.S. 

The results showed that a single dose of Ad26.COV2.S induced a strong neutralizing antibody response and was well tolerated in almost all participants aged 18 years and older.

But local adverse events were reported in 58 percent of Cohort 1 participants and 27 percent of Cohort 3 participants, researchers said. Solicited systemic adverse events were also reported in 64 percent of Cohort 1 participants and 36 percent of Cohort 3 participants. 

Serious adverse events are not uncommon in clinical trials, Johnson & Johnson noted. And the number of these adverse events may increase in trials involving large numbers of participants.

All studies conducted by pharmaceutical companies have prespecified guidelines, which ensure that a study may be paused or stopped if any unexpected serious adverse events related to the study product occur. 

When this happens, researchers will carefully review information and then decide when the study can re-start again. 

A study pause is done by the study sponsor and is a common component of clinical trial protocol, while a regulatory hold of a clinical trial is a requirement by regulatory health authorities, including FDA. 

“There is no greater priority than the safety and well being of the people we serve every day around the world,” Johnson & Johnson explained.  

“We are committed to providing transparent updates throughout the clinical development process of our vaccine candidate, in compliance with regulatory standards and our own high ethical and scientific principles.”

The pause is a setback for the company, which is seemingly behind its competitors in the “vaccine race,” The New York Times reported. 

However, its vaccine candidate does have several advantages compared to others currently being tested in clinical trials. Chief among the advantages is that the vaccine is a single dose whereas other pharmaceutical companies are developing a two-dose vaccine. 

Johnson & Johnson’s lead vaccine candidate also does not need to be frozen, which could ease manufacturing and distribution concerns.

But a trial pause does not indicate the end for Ad26.COV2.S.

At the beginning of September, AstraZeneca paused the clinical trial of its COVID-19 vaccine, AZD1222, due to an unexplained illness that occurred in the UK Phase III trial. 

AstraZeneca and the University of Oxford, as the trial sponsor, were not able to disclose further medical information.

But just a few weeks after, the company resumed the trial in the UK following confirmation by the Medicines Health Regulatory Authority that it was safe to do so.