Johnson & Johnson’s COVID-19 Vaccine Candidate Enters Phase 3 Trial


Johnson & Johnson has launched its large-scale phase 3 trial for Janssen’s COVID-19 vaccine candidate.

Vaccine clinical trial

Johnson & Johnson announced the initiation of its phase 3 clinical trial for Janssen’s coronavirus disease 2019 (COVID-19) vaccine candidate, JNJ-78436735, according to a press release.

Also known as Ad26.COV2.S, the investigational vaccine demonstrated positive interim results in the company’s phase 1/2a clinical study, which showed that the safety profile and immunogenicity after a single vaccination were supportive of further development.

The phase 3 ENSEMBLE trial will enroll up to 60,000 volunteers aged 18 years and older across 3 continents and will evaluate the safety and efficacy of a single vaccine dose compared with placebo in preventing COVID-19. The trial will include significant representation from those that are over the age of 60 years and will include individuals with and without comorbidities associated with an increased risk for progression in severe COVID-19. 

“With our vaccine candidate now in our global phase 3 trial, we are one step closer to finding a solution for COVID-19,” Mathai Mammen, MD, PhD, Global Head at Janssen Research & Development, LLC, Johnson & Johnson, said in a statement. “We used a highly scientific and evidence-based approach to select this vaccine candidate. We are extremely grateful for the tireless efforts of our researchers and for the vital contributions of those participants who have volunteered to take part in our studies. Together, we are working to help combat this pandemic.”

If successful in trials, the vaccine is estimated at launch to remain stable for 2 years at -20°C and at least 3 months at 2-8 °C, making it compatible with already existing standard vaccine distribution channels, effectively facilitating delivery to the public.

The company also said it has agreed to collaborate with the United Kingdom on a separate phase 3 clinical trial in multiple countries to explore a 2-dose regimen of Janssen’s vaccine candidate.

Johnson & Johnson said it anticipates the first batches of a COVID-19 vaccine to be available for emergency use authorization in early 2021, if proven to be safe and effective.


  1. Johnson & Johnson Initiates Pivotal Global Phase 3 Clinical Trial of Janssen’s COVID-19 Vaccine Candidate. News release. Johnson & Johnson; September 23, 2020. Accessed September 23, 2020.
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