It is likely that the effectiveness of the Covid-19 vaccines developed by Russia and China could be limited because both of them are based on a common cold virus that many people have been exposed to, said some experts.
The vaccine from CanSino Biologics that has been approved for the military in China is based on adenovirus type 5, or Ad5. According to a report published in the Wall Street Journal last week, the company is currently holding talks with a number of countries to get emergency approval of its use prior to completing large-scale trials.
Based on Ad5 and a second less common adenovirus, the Russian vaccine developed by Moscow’s Gamaleya Institute has been approved for use earlier this month without extensive testing.
“The Ad5 concerns me just because a lot of people have immunity,” said Anna Durbin, a vaccine researcher at Johns Hopkins University. “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.”
Many health experts believe that the novel coronavirus pandemic cannot be controlled without vaccines. The pandemic has already killed more than 845,000 people worldwide. Ad5 immunity issues would be addressed by its two-virus approach, Gamaleya has said.
Both the firms that developed the vaccines have approved Ebola vaccines based on Ad5 along with years of experience.
No comments on the issue were available from CanSino and Gamaleya.
For decades, Ad5-based vaccines have been worked upon with by researchers for treatment of a range of infections but have never been used. Thee vaccines use harmless viruses as “vectors” to ferry genes from the target virus which h in this case is the novel coronavirus, into human cells which prompts an immune response against the actual virus and hence fights the disease.
Experts also said that since many people already have developed antibodies against Ad5 in their bodies because of flue, therefore once the vaccines are injected into humans, the immune system will attack the vector instead of responding to the coronavirus which will make the vaccine less effective.
Alternative adenoviruses or delivery mechanisms are being used in many of the other current research for Cvoid-19 vaccines. For example, avoiding the Ad5 issue, a chimpanzee adenovirus formed the basis for the Covid-19 vaccine being developed by the Oxford University and AstraZeneca. And Ad26, a comparatively rare strain, is being used for its vaccine by Johnson & Johnson.
“The Oxford vaccine candidate has quite an advantage” over the injected CanSino vaccine, said Dr. Zhou Xing, from Canada’s McMaster University, worked with CanSino on its first Ad5-based vaccine, for tuberculosis, in 2011. An inhaled Covid-19 vaccine is being developed by his team which theorizes that pre-existing immunity issues could be circumvented.
There can be skepticism against vaccines because of flue that can be a result of high doses of the Ad5 vector in the CanSino vaccine, Xing also said.
“I think they will get good immunity in people that don’t have antibodies to the vaccine, but a lot of people do,” said Dr. Hildegund Ertl, director of the Wistar Institute Vaccine Center in Philadelphia.
(Source:www.reuters.com)
The vaccine from CanSino Biologics that has been approved for the military in China is based on adenovirus type 5, or Ad5. According to a report published in the Wall Street Journal last week, the company is currently holding talks with a number of countries to get emergency approval of its use prior to completing large-scale trials.
Based on Ad5 and a second less common adenovirus, the Russian vaccine developed by Moscow’s Gamaleya Institute has been approved for use earlier this month without extensive testing.
“The Ad5 concerns me just because a lot of people have immunity,” said Anna Durbin, a vaccine researcher at Johns Hopkins University. “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.”
Many health experts believe that the novel coronavirus pandemic cannot be controlled without vaccines. The pandemic has already killed more than 845,000 people worldwide. Ad5 immunity issues would be addressed by its two-virus approach, Gamaleya has said.
Both the firms that developed the vaccines have approved Ebola vaccines based on Ad5 along with years of experience.
No comments on the issue were available from CanSino and Gamaleya.
For decades, Ad5-based vaccines have been worked upon with by researchers for treatment of a range of infections but have never been used. Thee vaccines use harmless viruses as “vectors” to ferry genes from the target virus which h in this case is the novel coronavirus, into human cells which prompts an immune response against the actual virus and hence fights the disease.
Experts also said that since many people already have developed antibodies against Ad5 in their bodies because of flue, therefore once the vaccines are injected into humans, the immune system will attack the vector instead of responding to the coronavirus which will make the vaccine less effective.
Alternative adenoviruses or delivery mechanisms are being used in many of the other current research for Cvoid-19 vaccines. For example, avoiding the Ad5 issue, a chimpanzee adenovirus formed the basis for the Covid-19 vaccine being developed by the Oxford University and AstraZeneca. And Ad26, a comparatively rare strain, is being used for its vaccine by Johnson & Johnson.
“The Oxford vaccine candidate has quite an advantage” over the injected CanSino vaccine, said Dr. Zhou Xing, from Canada’s McMaster University, worked with CanSino on its first Ad5-based vaccine, for tuberculosis, in 2011. An inhaled Covid-19 vaccine is being developed by his team which theorizes that pre-existing immunity issues could be circumvented.
There can be skepticism against vaccines because of flue that can be a result of high doses of the Ad5 vector in the CanSino vaccine, Xing also said.
“I think they will get good immunity in people that don’t have antibodies to the vaccine, but a lot of people do,” said Dr. Hildegund Ertl, director of the Wistar Institute Vaccine Center in Philadelphia.
(Source:www.reuters.com)
