- A promising coronavirus vaccine candidate from China was able to protect monkeys from developing COVID-19 symptoms after being exposed to the virus.
- High doses of the vaccine worked better than a lower dose candidate, but even the latter led to a positive immune response.
- The vaccine has just started human trials, with phase II expected to begin in mid-May.
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The novel coronavirus has infected more than 2.75 million people in about four months, killing more than 192,000, as of Friday morning. Those are scary numbers and the virus will be with us for quite a while longer. It’s highly likely that more people will be infected and more will die of COVID-19 in the coming months and years. That’s because the world still lacks proper treatment options and vaccines likely at least still 18 months away. The good news, however, is that nearly 80 vaccine candidates are in the works and six of them have entered clinical trials. One of them comes from China, and it has been able to protect monkeys against various strains of COVID-19 that are wreaking havoc around the world.
The vaccine in question comes from Chinese Sinovac Biotech, reports ScienceMag. The company developed an “old-school” vaccine that uses a chemically inactivated version of the virus to trigger an immune response in the host. Researchers used the COVID-19 vaccine on rhesus macaque monkeys — if that type of monkey sounds familiar, it’s because other researchers in China proved the same species can’t be reinfected after surviving the disease.
The Sinovac team used two different doses of the vaccine on eight monkeys. Three weeks later, the monkeys were infected with the SARS-CoV-2 virus, which was placed right into their lungs via tubes inserted through their tracheas. None of the subjects developed a full-blown infection.
Monkeys who received a high dose developed the best response. Seven days after getting the virus, it was undetectable in the pharynx or lungs. Some of the animals given a lower dose showed a “viral blip,” but then controlled the infection. The company used a control group of four monkeys that were also given the vaccine, and they developed the expected symptoms. The virus replicated in various organs and caused severe pneumonia.
Even better, the researchers then used mixed antibodies from monkeys, rats, and mice given the vaccine against COVID-19 strains from China, Italy, Switzerland, Spain, and the United Kingdom. The antibodies neutralized all virus variations, which suggests SARS-CoV-2 mutations aren’t severe enough to prevent a vaccine from working.
The vaccine entered phase I of human trials on April 16th, recruiting 144 volunteers from the Jiangsu province. An equal number of participants will high and low doses or a placebo. Phase II might start by mid-May when 1,000 people will be included in the study, with the first conclusions to arrive by the end of June. A phase III trial will then compare the efficacy of the vaccine with the placebo using even bigger cohorts that will include thousands of people. After phase II, the study could be expanded to other countries that have more significant COVID-19 caseloads than China. Sinovac might partner with the WHO and local regulators to deploy the vaccine early to those people who are most at risk of contracting the disease, including healthcare workers, police, and first responders.
If successful, the company could produce up to 100 million doses of the vaccine and would need help from other vaccine makers and pharma companies. The nature of the vaccine is promising as well, according to Icahn School of Medicine at Mount Sinai virologist Florian Krammer. That’s because it’s “old school,” so it could be mass-produced by poorer countries and emerging markets.
While the early findings are promising, more research is required to determine the viability of the Sinovac vaccine. Some worry that the number of monkeys used is too small to yield relevant statistical data. Also, the virus used on the animals might differ slightly than the one spreading around the world. Finally, the monkeys do no experience the most severe symptoms that SARS-CoV-2 causes in humans.
The upcoming human trails will hopefully answer the lingering questions and provide additional data. The Sinovac research is available at this link in preprint form — that means it hasn’t yet been reviewed by peers.