Dublin, Ireland): China, the country that first detected the novel coronavirus, is one of the few countries that has not imported any of the extraordinarily effective mRNA COVID vaccines developed by Pfizer and Moderna. Instead, it has so far relied on vaccines developed by two Chinese companies, Sinovac and Sinopharm. Although China is now developing its own mRNA vaccine. Both Sinovac and SinoPharma vaccines use a traditional design, containing all forms of the coronavirus, that have been inactivated – a tried-and-tested method of making vaccines that work.
Although these vaccines were initially very good at preventing people from getting symptomatic COVID, this protection has eroded over time. These vaccines also do not provide adequate protection against infection with Omicron. This has put pressure on China to develop more effective vaccines, as it adopts a strict containment policy against the virus.
mRNA vaccines work in a different way. They carry a piece of the genetic code of the coronavirus in the body, which is housed inside a lipid droplet. Once it gets inside cells, the code is read and the cells make copies of its spike protein, an important part of the coronavirus. The immune system then sees these spike proteins and mounts a response to them, creating immunity against the incoming full-fledged virus.
The mRNA vaccines initially produced a high level of protection against COVID. Because the protection offered by two doses diminishes over time and provides little protection against infection with Omicron, mRNA vaccines provide the best protection against infection with Omicron when used as a booster. They provide very effective protection against serious disease. Early results suggest that a third dose of Sinovac is, by comparison, unable to prevent infection with the newer version (though these results are still in preprint, meaning they await review by other scientists).
China is making ARCOV It seems that mRNA vaccine technology will provide the best protection against Covid in the future – hence China is developing such a vaccine. However, he has not let anyone know much in this regard. The development of China’s own vaccine, ARCOV, to replace the mRNA, began in March 2020.
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The technology used is similar to that of the Pfizer and Moderna vaccines, which use a modified messenger RNA of the virus, placed in a lipid droplet, to enhance immunity. But like the Pfizer and Moderna vaccines, the virus has a full spike. Instead of preparing the immune system to deal with the protein, ARCOV makes copies of the receptor binding domain (RBD), a major subunit of the virus’s spike protein, which it uses to bind to and enter cells. .
This part of the virus is specifically recognized by the immune system, which suggests that targeting it may provide better protection. Another potential advantage of ARCOV compared to earlier mRNA vaccines is that it is stable at 2-8 °C for at least one month, which will greatly facilitate transportation, storage and distribution of the vaccine. How well does it work?
Results of a preliminary study of the vaccine in humans, where 120 volunteers were vaccinated with varying doses, were published in The Lancet in January 2022. The vaccine was found to be safe, but there was a higher rate of fever after vaccination, especially at higher doses, a result seen compared to early studies of other mRNA vaccines. However, this fever came only for a short time. The study also measured the levels of antibodies and T cells against the virus that the volunteers produced after vaccination.
The best antibody and T-cell responses were observed in the medium-dose group, with higher doses leading to lower responses. It is not 100% clear why this was so, but it may be due to the body’s non-specific immune response (its general purpose defense that attacks all kinds of external invaders), which has given the higher-dose vaccine its desired effect. Destroyed before reaching effect.
And even in those receiving intermediate doses, the recorded antibody and T-cell responses were lower than with existing mRNA vaccines, raising questions about how effective this vaccine would be. However, the results of an ongoing large-scale study are awaited to assess this properly. That large trial will involve more than 28,000 participants in China, Mexico and Indonesia and will use the intermediate dosage that was seen to work best in this initial study. Some interim results are expected in the coming months.
Another trial is also underway that is studying giving ARCOV as a booster after the Sinovac or SinoPharma vaccines. The results of these studies – both in terms of whether there are any adverse events and how well ARCov prevents infection, serious illness and death – will determine the future of this vaccine and China’s future approach to COVID. (agency)