A single-shot vaccine for COVID-19: Will it work? What you need to know about J&J’s phase 3 ENSEMBLE trial

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Johnson & Johnson coronavirus vaccine
  • Johnson & Johnson is starting the phase 3 clinical trial for its single-shot vaccine against the SARS-CoV-2
  • Researchers say a single immunization with the vaccine protects rhesus macaques against SARS-CoV-2
  • The global phase 3 ENSEMBLE study will involve 60,000 volunteers - 18 years old and older
As drug makers and scientists across the world race to produce a vaccine against novel coronavirus (SARS-CoV-2), the first single-shot COVID-19 vaccine has entered the late-stage, pivotal, phase 3 trial of clinical testing in the United States. On Wednesday, September 23, American pharmaceutical company Johnson & Johnson announced that it is initiating a large-scale global trial (ENSEMBLE) involving 60,000 volunteers across three continents for its COVID-19 vaccine candidate, JNJ-78436735, also known as Ad26.COV2.S.
The candidate being developed by Janssen Pharmaceutical Companies, a division of Johnson & Johnson, is the fourth vaccine to enter the phase 3 trials in the US. The investigational vaccine elicited an immune response against SARS-CoV-2, the virus that causes COVID-19, in a preclinical, non-human study. And here’s a brief summary of the Johnson & Johnson’s phase 3 ENSEMBLE study.

Facts about Johnson & Johnson’s single-shot COVID-19 vaccine phase 3 trial

  • Johnson & Johnson, in a press release, said the phase 3 clinical trial for its single-shot vaccine is a randomized, double-blind, placebo-controlled clinical trial designed to evaluate the safety and efficacy of a single vaccine dose versus placebo.
  • The phase 3 ENSEMBLE study will enroll up to 60,000 adults 18 years old and older, including significant representation from those who are over age 60.
  • The phase 3 trial will also include those both with and without comorbidities associated with an increased risk for progression to severe COVID-19.
  • The researchers will enroll participants in Argentina, Brazil, Chile, Colombia, Mexico, Peru, South Africa and the United States to assess the safety and efficacy of the single-dose vaccine dose in preventing COVID-19.
  • “In order to evaluate the effectiveness of Janssen’s COVID-19 vaccine, countries and clinical trial sites which have a high incidence of COVID-19 and the ability to achieve a rapid initiation will be activated,” the release said.
“As COVID-19 continues to impact the daily lives of people around the world, our goal remains the same - leveraging the global reach and scientific innovation of our company to help bring an end to this pandemic,” said Alex Gorsky, Chairman and Chief Executive Officer, Johnson & Johnson. “As the world’s largest healthcare company, we are bringing to bear our best scientific minds, and rigorous standards of safety, in collaboration with regulators, to accelerate the fight against this pandemic. This pivotal milestone demonstrates our focused efforts toward a COVID-19 vaccine that are built on collaboration and deep commitment to a robust scientific process. We are committed to clinical trial transparency and to sharing information related to our study, including details of our study protocol.”

Will a single-shot vaccine work against COVID-19?

A single immunization with the vaccine, Ad26.COV2.S, has proven successful on primates, according to a study published in the journal Nature. The researchers reported that the vaccine raised neutralizing antibodies and robustly protected rhesus macaques against SARS-CoV-2, the virus that causes COVID-19.
“This vaccine led to robust protection against SARS-CoV-2 in rhesus macaques and is now being evaluated in humans,” said Dan H Barouch, an immunologist at Beth Israel Deaconess Medical Center (BIDMC), who led the study and partnered with J & J to develop the vaccine.
Barouch’s team developed a series of vaccine candidates designed to express different variants of the SARS-CoV-2 spike protein, the major target for neutralizing antibodies, said a report in The Harvard Gazette.
“Our data show that a single immunization with Ad26.COV2.S robustly protected rhesus macaques against SARS-CoV-2 challenge. A single-shot immunization has practical and logistical advantages over a two-shot regimen for global deployment and pandemic control, but a two-shot vaccine will likely be more immunogenic, and thus both regimens are being evaluated in clinical trials. We look forward to the results of the clinical trials that will determine the safety and immunogenicity, and ultimately the efficacy, of the Ad26.COV2.S vaccine in humans,” added Barouch, who is director of BIDMC’s Center for Virology and Vaccine Research.
The phase 3 clinical trial will determine whether the vaccine can protect humans against the SARS-CoV-2 virus with a single-shot. 
According to Barouch, a single-shot vaccine, if it’s proven to be safe and effective, will have substantial logistic advantages in controlling the global pandemic.
The Ad26.COV2.S vaccine uses a common cold virus, called adenovirus serotype 26 (Ad26), to deliver the SARS-CoV-2 spike protein into host cells, where it stimulates the body to raise immune responses against the virus.
Johnson & Johnson said it is scaling up manufacturing of the vaccine and the company plans to produce more 1 billion doses globally through 2021.

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