Coronavirus: Chinese vaccine 'safe', triggers immune response

Henrietta Brewer
May 22, 2020

But in one study, monkeys developed immunity against the new SARS-CoV-2 coronavirus after receiving experimental vaccines.

In one of the new studies, researchers infected nine monkeys with COVID-19, the illness caused by the novel coronavirus.

"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.

CanSino Biologic, a Chinese vaccine company, is conducting phase two human trials of a COVID-19 vaccine, and the company has also received approval from Canada's Department of Health to carry out additional human trials in the country.

After two weeks, the vaccine produced virus-fighting antibodies across all dose levels, with the highest dose level triggering antibodies in 61 percent of those who took it.

In the paper, "SARS-CoV-2 infection protects against rechallenge in rhesus macaques", the group tested whether nine adult animals who had cleared the virus were immune to viral re-challenge 35 days later.

A Reuters poll published Thursday found that a quarter of Americans were not very or not at all interested in getting a vaccine for the virus that has infected more than 1.6 million people in the US. "These data suggest that it may be easier to protect against lower respiratory tract disease compared with upper respiratory tract disease", the researchers write.

They were then exposed to the virus alongside 10 control animals.

"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", Barouch said.

In all cases, as the production of immune system antibodies rose, viral load declined.

The authors of the study cautioned that further research will be needed because of the "important differences" between SARS-CoV-2 infection in monkeys and humans.

They were exposed to the coronavirus six weeks later and had developed levels of antibodies in the blood sufficient to neutralize it, the study found.

In fact, 8 of the 25 vaccinated monkeys showed no detectable virus at any point following exposure to SARS-CoV-2, and the other vaccinated animals showed only low viral loads, the researchers reported in the March 20 issue of the journal Science.

"Our findings increase optimism that the development of COVID-19 vaccines will be possible", said Barouch. Although we don't yet know how long the protection lasts, or if the same will be true in humans, the work bolsters hopes for a vaccine and lowers the chances our worst fears about the virus will be realized.

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