Although no clear cause of the illness has been identified, Johnson & Johnson says it has found no evidence that the vaccine candidate caused the event (it has not disclosed either the nature or severity of the illness).
A statement from the company issued on Friday [October 23] says it is preparing to resume the trial in the US, while discussions with other regulators around the world are ongoing.
“The independent Data Safety and Monitoring Board (DSMB) overseeing the ENSEMBLE study has recommended resuming trial recruitment. Following consultation with the U.S. Food and Drug Administration (FDA), preparations to resume the trial in the US, including submissions for approval by the Institutional Review Boards, are now underway. Discussions with other regulators around the world to resume the clinical trial program are progressing.
“After a thorough evaluation of a serious medical event experienced by one study participant, no clear cause has been identified. There are many possible factors that could have caused the event. Based on the information gathered to date and the input of independent experts, the Company has found no evidence that the vaccine candidate caused the event.”
In line with the clinical trial protocol and regulatory requirements, the Janssen study team remains blinded as to whether the unexplained illness was in the vaccine or placebo group.
It highlights that unexpected adverse events can occur in any clinical study, especially large studies.
“The full safety and efficacy results will be shared at the conclusion of the trial when we can present a complete assessment of the profile of our vaccine candidate to regulatory authorities for consideration.”
Viral vector technology
The Janssen COVID-19 vaccine candidate, JNJ-78436735 (also known as Ad.26.COV2.S), is a recombinant vector vaccine that uses a human adenovirus to express the SARS-CoV-2 spike protein in cells. It uses the company’s existing AdVac technology platform (used to develop and manufacture Janssen’s European Commission approved Ebola vaccine and construct its Zika, RSV, and HIV vaccine candidates).
Its Phase 3 trial was launched on September 23, setting out to enrol up to 60,000 people aged 18 and over in 215 sites in the US, Argentina, Brazil, Chile, Colombia, Mexico, Peru and South Africa.
Unlike a number of other frontrunners in the COVID-19 vaccine race, the Phase 3 trial is based on the vaccine requiring a single rather than double shot.
AstraZeneca’s viral vector candidate also suffered a setback when its Phase 3 trial was paused on September 6 due to an unexplained illness: but all trials globally have now recommenced.