COVID-19: Vaccine protects monkeys from new coronavirus
Chinese biotechnology Sinovac has created a vaccine that works in its first tests. One of the many vaccines in development against Covid-19 has protected an animal from contagion, it is the rhesus macaque. This is a chemically inactivated formulation of the virus, it produced no obvious side effects in monkeys, and human trials began on April 16.
The monkeys who received the highest dose of vaccine had the best response: Seven days after the animals received the virus, the researchers were unable to detect it in the pharynx or lungs of any of them. Some of the lower-dose animals had a "viral virus" but also appeared to have controlled the infection, Sinovac's team reports. In contrast, four control animals developed high levels of viral RNA in various parts of the body and severe pneumonia. The results "give us a lot of confidence" that the vaccine will work in humans, says Meng Weining, senior director of regulatory affairs abroad at Sinovac.
But Douglas Reed of the University of Pittsburgh, which is developing and testing COVID-19 vaccines in monkey studies, says the number of animals was too small to produce statistically significant results. His team also has a manuscript in preparation that raises concerns about how Sinovac's team increased the stock of new coronaviruses used to challenge animals: it may have caused changes that make it less reflective than those that infect humans.
Another concern is that monkeys do not develop the more severe symptoms that SARS-CoV-2 causes in humans. The Sinovac researchers acknowledge that "it is still too early to define the best animal model to study SARS-CoV-2," but noted that unvaccinated rhesus macaques that receive the virus "mimic symptoms similar to COVID-19."
SARS-CoV-2 claims to accumulate mutations slowly, but variants can be challenging for a vaccine. In test tube experiments, the Sinovac researchers mixed antibodies taken from monkeys, rats, and mice that received their vaccine with strains of the virus isolated from patients with COVID-19 in China, Italy, Switzerland, Spain, and the United Kingdom. The antibodies "neutralized" all strains that are "widely dispersed in the phylogenetic tree," the researchers said.
If successful, Meng says, Sinovac will seek to launch traditional phase III efficacy trials comparing the vaccine to a placebo in thousands of people. The company has also evaluated joining international vaccine trials organized by the World Health Organization. Given the low level of transmission now occurring in China, the company is considering even more efficacy trials in other countries that are more affected by the virus. "We can't put all of our eggs in one basket," says Meng.
According to the WHO, six other vaccines were in human trials as of April 23, and another 77 were in development. The vast majority of these vaccines use modern genetic engineering tools; Only four rely on outdated inactivation technology such as this one, but Meng says that what ultimately matters is whether a vaccine is safe and effective, not how it's made. "We are not comparing ourselves to anyone," says Meng. "In this pandemic situation, the most important thing is to make a vaccine, no matter what type of vaccine it is, that is safe and effective as soon as possible".