A medical worker instructs a woman to take a swab sample at a COVID-19 drive-thru testing site in Atlanta, Georgia, the United States, July 20, 2020. (Photo by Alan Chin/Xinhua)

 
A fourth Phase 3 clinical trial evaluating an investigational COVID-19 vaccine has begun enrolling adult volunteers, the US National Institutes of Health (NIH) announced on Wednesday.

The trial is designed to evaluate if the investigational Janssen COVID-19 vaccine JNJ-78436725 can prevent symptomatic COVID-19 after a single dose regimen, the NIH said in a release.

Up to 60,000 volunteers will be enrolled in the trial at up to nearly 215 clinical research sites in the United States and internationally.

The Janssen Pharmaceutical Companies of Johnson & Johnson developed the investigational vaccine, and is leading the clinical trial as regulatory sponsor.

It is the fourth large-scale phase 3 clinical trials for a COVID-19 vaccine in the United States. The other three trials are for vaccine candidate AZD1222, co-invented by the University of Oxford and its spin-out company Vaccitech; vaccine candidate mRNA-1273, developed by the US National Institute of Allergy and Infectious Diseases (NIAID) and American biotechnology company Moderna; and vaccine candidate BNT162b2, developed by American biopharmaceutical company Pfizer and German company BioNTech.

Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, testifies at a House subcommittee hearing in Washington, D.C., the United States, on July 31, 2020. U.S. top infectious disease expert Anthony Fauci said on Friday he is "cautiously optimistic" that the United States would have a safe and effective COVID-19 vaccine this late fall or early winter. (Kevin Dietsch/Pool via Xinhua)

 
While the other vaccine candidates require two doses, the Janssen vaccine candidate will be studied as a single-dose vaccine. It is a recombinant vector vaccine that uses a human adenovirus to express the SARS-CoV-2 spike protein in cells.

Preclinical findings published in Nature show that the Janssen 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 trial is designed primarily to determine if the investigational vaccine can prevent moderate to severe COVID-19 after a single dose. It also aims to understand if the vaccine can prevent COVID-19 requiring medical intervention and if the vaccine can prevent milder cases of COVID-19 and asymptomatic SARS-CoV-2 infection, according to the NIH.

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

"Four COVID-19 vaccine candidates are in Phase 3 clinical testing in the United States just over eight months after SARS-CoV-2 was identified. This is an unprecedented feat for the scientific community made possible by decades of progress in vaccine technology and a coordinated, strategic approach across government, industry and academia," said NIAID Director Anthony Fauci.

"It is likely that multiple COVID-19 vaccine regimens will be required to meet the global need. 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," Fauci said.