Coronavirus vaccine update: Russia's "World's first vaccine" Sputnik-V developed by Moscow-based Gamaleya Institute is also based on Ad5 and a second less common adenovirus, as per a Reuters report.
Coronavirus vaccine update: Oxford-AstraZeneca’s COVID19 vaccine candidate has quite an advantage over vaccines from Russia, and China, claimed experts. Experts have cited a potential shortcoming in the COVID-19 vaccines being developed by Russia and China. These experimental vaccines are based on a common cold virus that many people have been exposed to, potentially limiting their effectiveness, several experts have said.
China has already approved CanSino Biologics’ vaccine for emergency use. CanSino’s Coronavirus vaccine, which is undergoing Phase 3 human trials, is a modified form of adenovirus type 5, or Ad5. The company is in talks to get emergency approval in several countries before completing large-scale trials. Russia’s “World’s first vaccine” Sputnik-V developed by Moscow-based Gamaleya Institute is also based on Ad5 and a second less common adenovirus, as per a Reuters report.
Anna Durbin, a vaccine researcher at Johns Hopkins University, said, “The Ad5 concerns me just because a lot of people have immunity.” “I’m not sure what their strategy is … maybe it won’t have 70 per cent efficacy. It might have 40 per cent efficacy, and that’s better than nothing until something else comes along.”
Researchers have experimented with Ad5-based vaccines against a variety of infections for decades, but none are widely used. They employ harmless viruses as “vectors” to ferry genes from the target virus – in this case the novel coronavirus – into human cells, prompting an immune response to fight the actual virus. But many people already have antibodies against Ad5, which could cause the immune system to attack the vector instead of responding to the coronavirus, making these vaccines less effective, as per a Reuters report.
Several researchers have chosen alternative adenoviruses or delivery mechanisms. Oxford University and AstraZeneca based their COVID-19 vaccine on a chimpanzee adenovirus, avoiding the Ad5 issue. Johnson & Johnson’s candidate uses Ad26, a comparatively rare strain. “The Oxford vaccine candidate has quite an advantage,” said Dr. Zhou Xing, from Canada’s McMaster University. Zhou worked with CanSino on its first Ad5-based vaccine, for tuberculosis, in 2011. His team is developing an inhaled Ad5 COVID-19 vaccine, theorizing it could circumvent pre-existing immunity issues.
Some scientists also worry an Ad5-based vaccine could increase the chances of contracting HIV.