Women Scientists lead the South African leg of the Phase 3 Janssen Efficacy COVID-19 vaccine trial

Cape Town | South Africa has the biggest burden of COVID-19 infections in Africa and is the 10th most affected country globally. Without a COVID-19 vaccine, it is unlikely that South Africa or other heavily affected countries can control or eliminate SARS-CoV-2 without a vaccine in the short-term. South Africa is commencing a phase 3 efficacy vaccine trial with the Janssen Pharmaceutical Companies of Johnson & Johnson called the ENSEMBLE trial.

This is a large scale randomized, double-blind, placebo-controlled clinical trial that is designed to evaluate the safety and efficacy of Janssen’s investigational COVID-19 vaccine candidate, JNJ-78436735, also known as Ad26.COV2.S – the study is sponsored by Janssen Vaccines & Prevention B.V. The Department of Science and Innovation and the SAMRC is supporting community engagement for COVID-19 vaccine development.

The SAMRC is participating in the trial as part of the COVID-19 Prevention Network funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of the U.S. National Institutes of Health.

“This is the first international COVID-19 Vaccine trial sponsored by Operation Warp Speed and the NIH supported Coronavirus Prevention Network (CoVPN). It builds upon the longstanding collaborations in HIV that we have had with the citizens and investigators of South Africa,” said Prof Larry Corey, Principal Investigator of the COVPN Operations Center in Seattle. 

Leading the trial are two respected female scientists Profs Glenda Gray, President and CEO of the SAMRC and Linda-Gail Bekker Deputy Director, Desmond Tutu HIV Centre. With close to 215 clinical research sites including 31 in South Africa, the trial is expected to enroll up to 60,000 adult volunteers including significant representation from those who are over 60 years of age. The trial will also include those with and without comorbidities associated with an increased risk for progression to severe COVID-19. Persons who are HIV infected are who are stable on medication are not excluded from participation.

Considering the current disease prevalence and population demographics, clinical trial sites will be in seven provinces including Gauteng; North West; Eastern Cape; Western Cape; Limpopo; Mpumalanga and the Free State. “It’s important that South Africa participates in vaccine trials and contributes to the global cause, to ascertain the safety and efficacy of the various vaccine candidates,” said Bekker.

“This trial is a great feat for transformation as a women led study, with more than 60% Black investigators and over 60% women leading the research sites, representation of rural communities, as well as historically disadvantaged institutions, and a huge collaboration between academia and the private sector,” said Gray.

After providing a baseline nasopharyngeal and blood sample, participants will be assigned at random to receive either a single dose of the investigational vaccine or a saline placebo. Because the trial is blinded, neither investigators nor participants will know who is receiving the investigational vaccine. Participants will be followed closely for safety for over two years.

Scientists will analyze the blood samples to detect and quantify immune responses to COVID-19. Specialized assays will be used that can distinguish between immunity as a result of natural infection and vaccine-induced immunity.

Johnson & Johnson is committed to bringing an affordable COVID-19 vaccine to the public on a not-for-profit (NFP) basis for emergency pandemic use, provided the vaccine is efficacious, has a good safety profile and receives approval or authorisation from regulators.

About the Janssen vaccine candidate

The Janssen vaccine candidate is a recombinant vector vaccine that uses a human adenovirus to express the SARS-CoV-2 spike protein in cells. Adenoviruses are a group of viruses that cause the common cold. However, the adenovirus vector used in the vaccine candidate has been modified so that it can no longer replicate in humans and cause disease. Janssen uses the same vector in the first dose of its prime-boost vaccine regimen against Ebola virus disease (Ad26.ZEBOV and MVA-BN-Filo) that was recently granted marketing authorization by the European Commission.

Preclinical findings show that the investigational Janssen COVID-19 vaccine induced neutralizing antibody responses in rhesus macaques and provided complete or near-complete protection against virus infection in the lungs and nose following SARS-CoV-2 challenge. The safety, reactogenicity and immunogenicity of the investigational vaccine are being evaluated in a Phase 1/2a trial in the United States and Belgium enrolling adult volunteers. Positive interim results from the Phase 1/2a clinical study demonstrated that the safety profile and immunogenicity after a single vaccination were supportive of further development.


An independent Data and Safety Monitoring Board (DSMB) will provide oversight to ensure the safe and ethical conduct of the study.

More information about the trial is available at: www.ensemblestudy.com

Release date: 
Monday, November 9, 2020 - 09:16
Dumile Mlambo
Contact: Dumile Mlambo

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E-mail: Dumile.Mlambo@mrc.ac.za