US, WASHINGTON (ORDO NEWS) — Specialists from the Chinese company Sinovac Biotech have stated that the inactivated vaccine they are developing against Covid-19 has been shown to be effective in rhesus monkeys. A drug called PiCoVacc (purified inactivated SARS-CoV-2 virus vaccine candidate) protected animals from the virus without causing noticeable side effects.
The research article is available in the BioRxiv preprint archive.
The authors introduced two different doses of the vaccine (3 mg and 6 mg, respectively) to eight monkeys. Three weeks after the injection, the monkeys were injected with SARS-CoV-2 virus into the lungs by inhalation. After that, none of the experimental primates developed a full-blown coronavirus infection.
The double-dose macaques showed the best response to the vaccine: seven days after viral inhalation, scientists did not find traces of the virus in the throat and lungs of these animals. Some macaques who received 3 milligrams of the vaccine, according to scientists, observed a “glimpse of the infection”, which their body coped with without any difficulty. Moreover, all four monkeys from the control group that were infected with coronavirus without prior immunization developed a severe form of pneumonia, as well as high concentrations of viral RNA in all parts of the body.
The results of PiCoVacc research have already caused both approval and criticism from other scientists. “It’s an (inactivated vaccine – Ed.) Old school, but it might work,” says virologist Florian Kramer, who studies Covid-19 prevention and is a co-author of the status report for many vaccines. “What I like most is that many vaccine manufacturers, including in lower-middle-income countries, could make such a vaccine.”
Douglas Reed of the University of Pittsburgh, also testing monkey coronavirus vaccines, said the number of animals was too small to produce statistically significant results. Another important issue is that monkeys usually do not develop the most serious symptoms that SARS-CoV-2 causes in humans.
Sinovac experts in their article admit that their model for studying the anti-coronavirus vaccine is probably not the best, but they note that the infected monkeys from the control group “mimic symptoms similar to Covid-19.” The researchers also found no signs of lung damage in macaques that produced a relatively low level of antibodies, which was previously observed when testing vaccines against coronaviruses related to SARS-CoV-2.(A) Phylogenetic distribution of coronavirus strains; (B) Kinetics of PiCoVacc in Vero cell line cultures; (C) vaccine preparation schedule; (D) Electrophoregram of vaccine proteins; (E) Micrograph of viral particles / © Qin, Gao, Bao et al., 2020.
Sinovac also examined how mutation of the virus can reduce the effectiveness of the vaccine. For this, scientists mixed antibodies obtained from monkeys, mice, and rats with virus strains isolated from patients with COVID-19 in China, Italy, Switzerland, Spain, and the United Kingdom. Researchers report that antibodies neutralized all varieties of the virus, “widely scattered across the phylogenetic tree.”
The company’s specialists have already begun the first phase of clinical trials. They will be attended by 144 Chinese volunteers who will be given equal proportions of low and high doses, as well as a placebo. Although placebo is not commonly used in this phase of the study, this technique will help identify side effects of PiCoVacc. If everything goes well, the second phase of research will start in May.
According to WHO, at the moment six other vaccines against coronavirus have already been tested in humans, and another 77 are under development. The vast majority of these drugs are created using modern genetic engineering tools, and only four, like PiCoVacc, are based on inactivation technology.
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