A phase 3 trial evaluating the vaccine candidate, JNJ-78436735 (Ad26.COV2.S; Janssen), for the prevention of coronavirus disease 2019 (COVID-19) has been initiated.

JNJ-78436735 is a recombinant vector vaccine that utilizes the Company’s AdVac® technology. It works by using a human adenovirus to express the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein.

The randomized, double-blind, placebo-controlled phase 3 ENSEMBLE trial will assess the efficacy and safety of JNJ-78436735 in up to 60,000 adults, including a significant number of individuals over 60 years of age. Patients will be randomized to receive JNJ-78436735 or placebo intramuscularly as a single dose regimen.

An independent Data and Safety Monitoring Board will provide oversight to ensure the safe and ethical conduct of the study. The study is being initiated in collaboration with the Biomedical Advanced Research and Development Authority and the National Institute of Allergy and Infectious Diseases (NIAID).

“Four COVID-19 vaccine candidates are in phase 3 clinical testing in the United States just over 8 months after SARS-CoV-2 was identified,” said NIAID Director Anthony S. Fauci, MD. “The Janssen candidate has showed promise in early-stage testing and may be especially useful in controlling the pandemic if shown to be protective after a single dose.”

The initiation of the ENSEMBLE study was based on positive interim results from a phase 1/2a clinical study, which demonstrated the safety and immunogenicity of JNJ-78436735, supporting further development of the vaccine. Moreover, preclinical findings showed JNJ-78436735 induced neutralizing antibody responses in rhesus macaques and provided complete or near-complete protection against virus infection in the lungs and nose after SARS-CoV-2 challenge.

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Adults interested in participating in the trial can visit coronaviruspreventionnetwork.org.

For more information visit nih.gov.


  1. Johnson & Johnson initiates pivotal global phase 3 clinical trial of Janssen’s COVID-19 vaccine candidate. https://www.prnewswire.com/news-releases/johnson–johnson-initiates-pivotal-global-phase-3-clinical-trial-of-janssens-covid-19-vaccine-candidate-301136522.html. Accessed September 23, 2020. 
  2. Fourth large-scale COVID-19 vaccine trial begins in the United States. https://www.nih.gov/news-events/news-releases/fourth-large-scale-covid-19-vaccine-trial-begins-united-states. Accessed September 23, 2020.