SCIENCE - For the first time, one of the many COVID-19 vaccines in development has protected an animal, rhesus macaques, from infection by the new coronavirus, scientists report. The vaccine, an old-fashioned formulation consisting of a chemically inactivated version of the virus, produced no obvious side effects in the monkeys, and human trials began on 16 April.
Researchers from Sinovac Biotech, a privately held Beijing-based company, gave two different doses of their COVID-19 vaccine to a total of eight rhesus macaques. Three weeks later, the group introduced SARS-CoV-2, the virus that causes COVID-19, into the monkeys’ lungs through tubes down their tracheas, and none developed a full-blown infection. The monkeys given the highest dose of vaccine had the best response: Seven days after the animals received the virus, researchers could not detect it in the pharynx or lungs of any of them.
Douglas Reed, associate professor of immunology, infectious diseases and microbiology at the University of Pittsburgh, is developing and testing COVID-19 vaccines in monkey studies. He says the number of animals was too small to yield statistically significant results. His team also has a manuscript in preparation that raises concerns about the way the Sinovac team grew the stock of novel coronavirus used to challenge the animals: It may have caused changes that make it less reflective of the ones that infect humans.
Other concerns include that monkeys do not develop the most severe symptoms that SARS-CoV-2 causes in humans and worries that partial protection could be dangerous. Earlier animal experiments with vaccines against the related coronaviruses that cause severe acute respiratory syndrome and Middle East respiratory syndrome had found that low antibody levels could lead to aberrant immune responses when an animal was given the pathogens, enhancing the infection and causing pathology in their lungs. But the Sinovac team did not find any evidence of lung damage in vaccinated animals who produced relatively low levels of antibodies. This “lessens the concern about vaccine enhancement,” Reed says. “More work needs to be done though.”
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COVID-19 vaccine protects monkeys from new coronavirus, Chinese biotech reports, by Jon Cohen, Science , Apr. 23, 2020 , 1:05 PM