COVID-19: Vaccine candidate developed in China reported to have protected monkeys

SARS-CoV-2 was directly put into the lungs of eight Rhesus Macaques. None of the monkeys that had been vaccinated were seen to have developed a full-blown infection.

April 25, 2020 by Sandipan Talukdar

While the rush for a vaccine against COVID-19 is on, new candidate vaccines are continuing to enter the initial human trial phase. The one developed by a Beijing-based Biotech company, Sinovac Biotech, is reported to have been used on Rhesus Macaque monkeys, apparently protecting them from the novel coronavirus causing COVID-19. The candidate vaccine has also been tried on humans since April 16 and is in phase I of the clinical trial.

The study was uploaded in the pre-print server BioRxiv on April 19. Researchers from Sinovac applied two different doses of their vaccine candidate to a total of eight monkeys from the species. After three weeks, they introduced the SARS-CoV-2, the coronavirus that causes COVID-19, directly into the lungs of the monkeys with the help of tubes down their windpipes. None of the monkeys that had been vaccinated were seen to have developed a full-blown infection.

Those that had a higher dose of the vaccine had the best response. Seven days after the virus entered their lungs, Sinovas researchers could not detect it in the pharynx or the lungs in any of the monkeys.

On the other hand, four monkeys that had not got the vaccine but had received the infection had high loads of viral RNA, and developed severe pneumonia. The result brings hope to researchers that the vaccine will be effective in humans as well.

The Sinovac Biotech’s vaccine candidate has been developed by using an old technique, which entails having a version of the virus that is chemically inactive. Notably, amid the COVID-19 pandemic, the unprecedented rush of vaccine development has led researchers to apply a plethora of new techniques like the RNA vaccine technique. In this scenario, an effective vaccine developed with the help of an older, more familiar technique, undoubtedly brings hope.

Florian Krammer, a virologist at the Icahn School of Medicine at Mount Sinai said he was positive about the vaccine. He reportedly said that despite being “old school”, it might work. “What I like most is that many vaccine producers, also in lower–middle-income countries, could make such a vaccine,” he was quoted saying.

Douglas Reed of the University of Pittsburgh, who is also developing a vaccine against COVID-19 said the number of monkeys it had been tested on were too less for any significant statistical conclusion to be reached.

Another concern is whether monkeys were a good model to study the infection as they do not develop the more severe symptoms as seen in humans. The Sinovac researchers also expressed a similar concern in their paper. But, it is also true that unvaccinated monkeys developed conditions similar to those seen in humans.

Sinovac has prior experience in vaccine development with the company having previously developed and marketed vaccines against Hepatitis A, Hepatitis B and H5N1 influenza, or the bird flu.

Meng Weining, Sinovac’s senior director for overseas regulatory affairs was quoted to have said that his company could only produce 100 million doses, at most. And if the COVID-19 vaccine turns out to be effective, the company might have to partner with other makers.

The vaccine candidates of Sinovac have entered the first phase of clinical trials in Jiangsu province, north of Shanghai, and have recruited 144 volunteers. An equal number of participants are to receive high and low doses and it is hoped that the company will be able to go for the second phase by mid-May with the result of that trial possibly due in June.

As of April 23, the vaccine candidates under clinical trial have gone up to six, according to WHO. Notably, out of these six candidate vaccines, the one developed by another Chinese joint venture—Cansino Biologicals and Beijing Institute of Technology, has already entered phase II of the clinical trial.

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