Russian and Chinese vaccines could have limited effectiveness, scientists say
Covid-19 vaccines developed in Russia and China could have limited effectiveness as they are created using the common cold virus that many people have been exposed to.
CanSino Biologics’ vaccine, approved for military use in China and the vaccine developed by Moscow’s Gamaleya, are a modified form of adenovirus type 5, or Ad5.
According to scientists from the John Hopkins University: “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% efficacy. It might have 40% efficacy, and that’s better than nothing, until something else comes along.”
Gamaleya has said its two-virus approach will address Ad5 immunity issues.
Vaccines, which are seen as essential to ending the pandemic that has claimed over 845,000 lives worldwide are being rushed by many pharma companies around the world and some are experimenting with Ad5-based vaccines.
Researchers have experimented with Ad5-based vaccines against a variety of infections for decades, but none are widely used, reported Reuters.
Many people 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.
Dr. Zhou Xing, from Canada’s McMaster University also worries that high doses of the Ad5 vector in the CanSino vaccine could induce fever, fueling vaccine skepticism.
There are also concerns regarding the Russian vaccine particularly after the government declared its intention to give it to high-risk groups in October without data from large pivotal trials.