Coronavirus: two vaccines enter human trials, 60 in pre-clinical stage

Include non-replicating viral vector and messenger RNA vaccines

April 11, 2020 06:10 pm | Updated 08:19 pm IST

Clinical trials:  Forty-five subjects, 18 to 55 years of age, of both sexes, will enrol in tests.

Clinical trials: Forty-five subjects, 18 to 55 years of age, of both sexes, will enrol in tests.

With the genetic information of the novel coronavirus (SARS-CoV-2) available online, governments across the globe, top private players, academics and not-for-profit organisations are working at a breakneck pace to find a COVID-19 vaccine.

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.

RNA vaccine

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.

According to the website, forty-five subjects (18 to 55 years of age of both sexes) will be enrolled and divided into three groups. They will receive an intramuscular injection on days 1 and 29 in the deltoid muscle.

An analysis published on April 9 in Nature Reviews Drug Discovery by the Coalition for Epidemic Preparedness Innovations (CEPI) notes that “the global COVID-19 vaccine R&D landscape includes 115 vaccine candidates, of which 78 are confirmed as active and 37 are unconfirmed (development status cannot be determined from publicly available or proprietary information sources).” Along with the two vaccines mentioned by WHO, the list includes one vaccine developed by Inovio Pharmaceuticals and two from Shenzhen Geno-Immune Medical Institute.

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.

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