Coronavirus: Monkeys resist re-infection after vaccine immunisation in USA study

Modesto Morganelli
Mag 22, 2020

Antibody production seen in the patients is a good sign that the vaccine may protect them from infection, but it's too soon to say for sure. "In these two studies, we demonstrate in rhesus macaques that prototype vaccines protected against SARS-CoV-2 infection and that SARS-CoV-2 infection protected against re-exposure".

"Upon second exposure, the animals demonstrated near-complete protection against the virus", researchers said.

"The global COVID-19 pandemic has made the development of a vaccine a top biomedical priority, but very little is now known about protective immunity to the SARS-CoV-2 virus", said Dan H. Barouch, MD, PhD, professor of medicine, Harvard Medical School, director, Center for Virology and Vaccine Research, BIDMC, and senior author on both studies. After they recovered, the team exposed them to the virus again and the animals did not get sick.

The Beijing Institute of Biotechnology's vaccine is just one of dozens being studied around the world as public health authorities desperately search for a cure for the pandemic, which has already killed more than 94,000 people in the USA alone.

These studies, which have been peer reviewed, do not prove that humans develop immunity or how long it might last, but they are reassuring. Instead their viral loads started low and declined rapidly.

It uses a weakened common cold virus (adenovirus, which infects human cells readily but is incapable of causing disease) to deliver genetic material that codes for the SARS-CoV-2 spike protein to the cells. And the monkeys showed hardly any symptoms.

Additional research will be required to define the durability of natural immunity shown here, the authors noted. Further trials are needed to tell whether the immune response it elicits effectively protects against SARS-COV-2 infection, said the medical journal.

Blood samples from a group of 108 vaccinated adults showed both neutralizing antibodies and T-cell responses against the novel coronavirus in most of those tested.

Barouch's team reports in Science that 35 days after the original infection, they gave the monkeys the same doses of SARS-CoV-2 as each had received initially.

With only four or five animals getting each vaccine, comparisons need to be treated with caution, but the monkeys receiving certain vaccines showed dramatically lower levels of virus throughout their bodies compared to the controls.

"While data from humans will require rigorous clinical trials, these data in an animal model increases our optimism that the development of a vaccine for humans will be possible", Dr Barouch said.

"Our study provided a new vaccine platform simulating coronavirus surface protein and internal nucleic acids, therefore, combining features of inactivated vaccines and mRNA vaccines", the researchers added.

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