Scientists at the Jenner Institute at Oxford University in the United Kingdom announced Monday that their potential vaccine against the new coronavirus passed a new stage with positive results: it worked successfully in rhesus macaque monkeys, perhaps the closest animal to humans in biological terms.
The institute is ahead in this type of effort – it has already begun its tests on hundreds of humans, a stage more advanced than those that have begun to do so in dozens – and advanced in positive initial testing, and with emergency approvals, it could have the first million doses in September.
The scientists explained that last month they inoculated six monkeys of this species with the potential vaccine. They were then exposed to high doses of Covid-19, which had sickened other monkeys. However, these six specimens are in good health 28 days after receiving the vaccine .
Dr. Vincent Muster, the scientist who led the study, clarified that they are still analyzing the results, but announced that he plans to share them next week and then refer it to a publication for evaluation by other colleagues .
Achieving immunity in monkeys, however, does not mean that the vaccine will work in humans. But Dr. Munster indicated that “the rhesus macaque is practically the closest thing to humans we have .”
The Jenner Institute is not the only group that has tested its vaccine on monkeys. Sinovac Biotech, a private company based in Beijing, announced similar results late last week. All of the monkeys inoculated in that case were also immune to the disease, while four of the control group developed high levels of viral RNA in various parts of the body and severe pneumonia.
Another encouraging fact was that the vaccine was effective against different variants of the disease. SARS-CoV-2 appears to accumulate mutations slowly, which can be challenging for treatments. In test tube experiments, 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 the strains, which are “widely dispersed in the phylogenetic tree,” the researchers noted.
However, different professionals have expressed doubts about how conclusive these studies are for two reasons: that the number of monkeys is not large enough to produce statistically significant results. And that monkeys do not develop the more severe symptoms that SARS-CoV-2 causes in humans.
In fact, the Sinovac researchers acknowledge in the document that “it is still too early to define the best animal model to study SARS-CoV-2”, but noted that unvaccinated rhesus macaques receiving the virus “mimic symptoms similar to COVID-19 ”.
“This provides strong evidence that the virus is not mutating in a way that would make it resistant to the COVID19 vaccine,” immunologist Mark Slifka of Oregon Health & Science University tweeted. “Good to know.”
The difference between the stages in which the Jenner Institute vaccine is found and Sinovec has to do with the fact that the first one managed to skip an initial stage of human testing and was able to start giving the vaccine to hundreds of people. This is because they had previously proven that similar vaccines did not cause harm to humans, the goal of the first stage of vaccination.
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In total, it is expected that in the clinical trial led by Oxford there will be 1,102 participants in different laboratories in the cities of Southampton, London, and Bristol.
The British Government has made £20 million (€ 22.60 million) available to the Oxford team and a further £22 million (€ 24.90 million) for the Imperial College project.
British Government Medical Adviser Chris Whitty has said the prospect of the work at Oxford University translating into an effective and safe vaccine that can be distributed this year is “incredibly small.”