August 10, 2020

The development of a safe and effective vaccine is a key step in ending the COVID-19 pandemic. A group of scientists now report that a leading candidate COVID-19 vaccine raises neutralizing antibodies and robustly protects non-human primates against SARS-CoV-2, the virus that causes COVID-19. The study was published July 30 in the journal Nature.

“This vaccine, [which was developed at Beth Israel Deaconess Medical Center (BIDMC) in collaboration with Johnson & Johnson,] led to robust protection against SARS-CoV-2 in rhesus macaques and is now being evaluated in humans,” said Dan H. Barouch, MD, PhD, director of BIDMC’s Center for Virology and Vaccine Research.

Dr. Ralph Baric

Dr. Ralph Baric

Dr. David Martinez

Dr. David Martinez

Paper co-authors from the UNC Gillings School of Global Public Health include Ralph Baric, PhD, William R. Kenan, Jr. Distinguished Professor of epidemiology, and David Martinez, PhD, a postdoctoral scholar in the Baric Lab.

“The Baric Lab has developed a SARS-CoV-2 neutralization assay,” Martinez explained. “Using this assay, we were able to measure antibody responses elicited by the vaccine in rhesus macaques.”

The 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 coronavirus. Barouch has been working on the development of a COVID-19 vaccine since January, when Chinese scientists released the SARS-CoV-2 genome. His team developed a series of vaccine candidates designed to express different variants of the SARS-CoV-2 spike protein, which is the major target for neutralizing antibodies.

The researchers then conducted a study in 52 non-human primates, immunizing 32 adult rhesus macaques with a single dose of one of seven different versions of the Ad26-based vaccine and giving 20 animals sham vaccines as placebo controls. All the vaccinated animals developed neutralizing antibodies following immunization.

Six weeks after the immunization, all the animals were exposed to SARS-CoV-2. Each of the 20 animals that received the sham vaccine became infected and showed high levels of virus in their lungs and nasal swabs. Of the six animals that received the strongest vaccine candidate — Ad26.COV2.S — none showed virus in their lungs, and only one showed low levels of virus in nasal swabs.

Moreover, Baric Lab researchers found that neutralizing antibody responses correlated with protection, suggesting that this biomarker will be useful in the clinical development of COVID-19 vaccines for use in humans.

“Our data show that a single immunization with Ad26.COV2.S robustly protected rhesus macaques against SARS-CoV-2,” said Barouch. “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.”

Investigators at BIDMC and other institutions have initiated a first-in-human Phase 1/2 clinical trial of the Ad26.COV2.S vaccine in healthy volunteers. Pending clinical trial outcomes, the Ad26.COV2.S vaccine is on track to start a Phase 3 efficacy trial in 30,000 participants in September.

Martinez added: “We hope these promising findings in monkeys will translate to a vaccine that works in humans and has the potential to end the COVID-19 pandemic.”

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