Three weeks after being vaccinated, the animals came into contact with the new coronavirus – and none of them developed severe symptoms of infection.
For the first time, one of the vaccines being studied for the prevention of COVID-19 worked when tested on animals, more specifically on monkeys. The drug is a chemically inactivated version of the virus that, when it comes into contact with the immune system, promotes the development of antibodies against the new coronavirus.
The vaccine is being developed by a group of researchers from Sinovac Biotech, located in Beijing, China. The scientific article published by the team is still being reviewed by other scientists, but a previous version of the document was shared on bioRxiv last Sunday (19).
In the tests, the scientists administered two different doses of the vaccine to a total of eight rhesus monkeys (Macaca mulatta). Three weeks later, the group introduced Sars-CoV-2 into the animals’ lungs through tubes in the trachea – and none of them developed a complete infection.
The monkeys that received the highest dose of vaccine had the best response: seven days after coming into contact with the coronavirus, the researchers were unable to detect it in the animals’ pharynx or lungs. Some of the guinea pigs that received lower doses had a “viral outbreak”, but they also controlled the infection.
Monkeys that were not vaccinated and came into contact with Sars-CoV-2 had high levels of viral RNA in various parts of the body and developed severe pneumonia. The results give confidence that the vaccine will work in humans, says Meng Weining, director of Sinovac, according to Science.
The drug must now undergo clinical trials and be administered to 144 individuals to determine whether it is safe. After that, the vaccine will be tested on 1,000 people for scientists to assess its effectiveness. Evidently, volunteers are not at risk of contracting Covid-19.
The technology used in the vaccine is old, but, according to experts, it continues to be used because it is effective. “What I like most is that many vaccine producers, also in lower–middle-income countries, could make such a vaccine,” said Florian Krammer, a professor in the Department of Microbiology at the Icahn School of Medicine at Mount Sinai, in New York City, on his Twitter.
However, other researchers, who studied the pre-published version of the article, say the test was done on a very small number of animals and consider that the coronavirus affects monkeys and humans in different ways. “More work needs to be done,” said Douglas Reed, of the University of Pittsburgh, who is also testing vaccines to prevent Covid-19.
Lucy Walker, a professor of immunological tolerance and regulation at University College London, who did not participate in the research, said on Twitter that it is necessary to analyze “whether the vaccine provides lasting protection”. That is, it is necessary to find out if the immunization generated by the drug will be continuous: “This is a fundamental question,” she wrote.