EXPLAINED: Biological E's Corbevax Approved For 12-18 Age Group. Here Is How The Vaccine Works

Biological E’s Corbevax is India’s first indigenously developed receptor-binding domain (RBD) protein sub-unit vaccine against Covid-19. The RBD is a part of the spike protein of SARS-CoV-2.

The DCGI has granted emergency use approval to Biological E's Corbevax for inoculating adolescents aged 12-18 years. Corbevax is India’s first indigenously developed receptor-binding domain (RBD) protein sub-unit vaccine against Covid-19. | Photo: Twitter/@ANI

New Delhi: The Drugs Controller General of India (DCGI) on Monday granted emergency use approval to Biological E's Covid-19 vaccine 'Corbevax' for inoculating adolescents aged 12-18 years. Biological E said in a statement that Corbevax has received emergency use authorisation (EUA) from the DCGI for the 12-to-18 age group.

Last year, on December 28, the Central Drugs Standard Control Organisation (CDSCO) had approved Corbevax for restricted use in emergency situation in adults.

Corbevax is India's third indigenous Covid-19 vaccine after Covaxin and Zydus Cadila's ZyCoV-D. 

Biological E’s Corbevax is India’s first indigenously developed receptor-binding domain (RBD) protein sub-unit vaccine against Covid-19. The RBD is a part of the spike protein of SARS-CoV-2. The virus uses the spike protein to attach itself to host cells.

What Is An RBD Protein Sub-Unit Vaccine?

Sub-unit vaccines, also called acellular vaccines, contain purified pieces of a pathogen, which have been specifically selected for their ability to stimulate immune cells, according to an article published by Gavi, the Vaccine Alliance — a public-private global health partnership that helps vaccinate almost half of the world’s children against deadly and debilitating infectious diseases.

Sub-unit vaccines are of different types, and are considered safe because the purified fragments are incapable of causing disease. These vaccines include only the parts of a virus that best stimulate one’s immune system, according to a Mayo Clinic article.

Protein sub-unit vaccines contain specific isolated proteins from viral or bacterial pathogens, and are being developed against SARS-CoV-2. Hepatitis B vaccines are other examples of protein sub-unit vaccines. 

An RBD protein sub-unit vaccine against Covid-19 makes use of a specific part of SARS-CoV-2 ­— the spike protein. It is a recombinant vaccine, which means it is manufactured using living organisms such as yeast cells.

RBD protein sub-unit vaccines are suitable for people with compromised immune systems, consist of no live components, as a result of which there is no risk of the vaccine triggering disease, and are relatively stable. However, they are more complex to manufacture, compared to other Covid-19 vaccines. Also, adjuvants and booster shots may be required after receiving the primary vaccination doses. 

How Does An RBD Protein Sub-Unit Vaccine Work?

An RBD protein sub-unit vaccine is one which induces protective immunity by targeting the RBD of the S protein of SARS-CoV-2, which is a harmless protein. The vaccine comprises residues of the RBD protein, according to a study published in the journal, Nature.

The residues of the RBD protein used in the vaccine are carefully studied to identify which combinations of the molecules are likely to produce a strong and effective immune response, according to the Gavi article. The body develops an immune response against the injected fragments of the spike protein.

The immune system recognises the S proteins, and creates antibodies and defensive white blood cells. These antibodies will fight the virus if the person becomes infected with the Covid-19 virus in future.

An RBD protein sub-unit vaccine, like Corbebax, helps the immune system recognise the S proteins and create antibodies.