China, the country that first detected the novel coronavirus, remains one of the few not to have imported one of the exceptionally 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. However, this may be set to change. China is now developing its own mRNA vaccine.
Both the Sinovac and Sinopharm vaccines use a traditional design, containing whole forms of the coronavirus that have been inactivated – a tried-and-tested way of making vaccines that work.
However, while these vaccines were initially quite good at stopping people getting symptomatic COVID, this protection waned significantly over time. These vaccines also offer poor protection against infection with omicron. This has put pressure on China to develop more effective vaccines, as it is pursuing a strict containment policy with the virus.
The mRNA vaccines work in a different way. They deliver a snippet of the coronavirus’s genetic code into the body, housed inside a lipid droplet. Once this gets inside cells, the code gets read and the cells produce copies of a key part of the coronavirus, its spike protein. The immune system then sees these spike proteins and mounts a response to them, generating immunity against the full virus should it be encountered in the future.
The mRNA vaccines initially generated high levels of protection against getting COVID. And while the protection offered by two doses wanes over time and offers little protection against infection with omicron, the mRNA vaccines appear to offer the best protection against an omicron infection when used as boosters. They also continue to offer very impressive protection against severe disease. Early results suggest a third dose of Sinovac, in comparison, is unable to stop infection with the new variant (though these results are still in preprint, meaning they’re awaiting review by other scientists).