Coronavirus: two vaccines enter human trials, 60 in pre-clinical stage
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Include non-replicating viral vector and messenger RNA vaccines
- According to the “DRAFT landscape of COVID-19 candidate vaccines” released by the World Health Organization (WHO) on April 4, two vaccines are currently being tested on humans.
- This includes a non-replicating viral vector vaccine developed by CanSino Biological Inc. along with the Beijing Institute of Biotechnology. A non-replicating vector vaccine can be developed either using a virus that is killed or a part of the virus.
- Since it is not a complete virus, it cannot replicate inside the host; but the antigens trigger our immune system to produce antibodies, which help fight the disease in case we contract it in the future.
- According to the Chinese Clinical Trial Registry, men and women between the ages of 18 and 60 were recruited and tests are being conducted on three groups of 36 participants each. Three dosages are being tested — low, medium and high.
- The second is a messenger RNA vaccine developed by Moderna and National Institute of Allergy and Infectious Diseases. In RNA vaccines, the messenger RNA from the pathogen is used.
- The messenger RNA gets translated into antigenic protein recognised by our immune cells and antibodies are produced. But mRNA is a highly unstable molecule making it difficult to handle.
- So the mRNA is encapsulated in a small ball of fat or lipid nanoparticle (LNP). This LNP acts as a delivery vehicle that helps the mRNA cross the host cell membrane and once inside the mRNA is released.
Vaccines from India
- The WHO draft adds that 60 candidate vaccines are in preclinical trials. This list contains the DNA plasmid vaccine developed by Gujarat based Zydus Cadila and Live Attenuated Virus vaccine developed by the Serum Institute of India.
- DNA vaccines are made by taking genes from the pathogen and inserting it into the host's body with a vector. The host cells produce the protein of the viral gene and this is recognised as a foreign antigenic protein by the host’s immune system.
- DNA vaccines are comparatively easy to make, transport, store and are cheaper. Live attenuated virus vaccine is created by reducing the virulence of a pathogen or weakening it, but still keeping it alive.