Johnson & Johnson Paused COVID Vaccine Trial after unexplained illness of participant

Johnson & Johnson have temporarily stopped its Covid-19 vaccine trial. The trial was stopped in the backdrop of one of its participants became sick during the trial.


  • Giving further doses to all Covid-19 vaccine candidate clinical trials has been stopped.
  • Phase 3 ENSEMBLE trial has also been stopped temporarily.
  • One of the trial participant fell ill, reason for which is still unknown.
  • After this has been  paused, the online enrolment system has also been closed for the 60,000-patient clinical trial.


Johnson & Johnson had announced the launch of its large-scale, pivotal, multi-country Phase 3 trial (ENSEMBLE) for its COVID-19 vaccine candidate on September 23, 2020. The initiation of the ENSEMBLE trial followed the positive interim results from the Company’s Phase 1 and 2 clinical study. The phase 1 and phase 2 trials had demonstrated that the safety profile and immunogenicity were supportive of further development after single dose. ENSEMBLE then enrolled up to 60,000 volunteers across more than 200 sites in the US and other continents. Apart From US, countries like Argentina, Brazil, Chile, Mexico, Peru, Colombia and South Africa are involved in the trial.


This study is a randomized, double-blind, placebo-controlled clinical trial. The phase 3 has been designed to evaluate the safety and efficacy of a single vaccine dose versus the placebo in up to 60,000 adults. The candidates’ age is ranging from 18 years old to 60 year old. ENSEMBLE has been initiated in collaboration with the Biomedical Advanced Research and Development Authority (BARDA) and Response at the U.S. Department of Health and Human Services (HHS).