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Explained: What is Corbevax, the vaccine approved for your 5-year-old kid?

The national drugs controller has cleared children as young as 5 years old to be vaccinated with Biological E’s Corbevax. How was the vaccine made, and how does it work? How is it different?

Covid-19 vaccination drive for age group 12-14 years at Apeejay school at Nerul, Mumbai. (Express photo by Narendra Vaskar)

As schools around the country return to full in-person classes, and amid reports of some small children testing positive for Covid-19, the national drugs controller on Tuesday (April 26) cleared children as young as 5 years old to receive vaccination against the coronavirus.

Once the modalities for the rollout are finalised by the government, kids in the age group of 5-12 can be vaccinated with Biological E’s Corbevax.

The United States and United Kingdom have allowed vaccination of children age 5 with Pfizer/BioNTech’s mRNA vaccine. Corbevax, which is being used at present to vaccinate pre- and young teens in the 12-14 years age group, is built on a different technological platform.

Also on Tuesday, the Drugs Controller General of India (DCGI) granted emergency use authorisation (EUA) to Bharat Biotech’s Covaxin for kids in the age group of 6-12 years, and to Gujarat-based Zydus Cadila’s two-dose vaccine for recipients above the age of 12 years.

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Zydus Cadila’s vaccine is the world’s first Covid-19 vaccine built on a DNA platform that has been approved for commercial use. A three-dose version of Zydus Cadila’s vaccine is already part of the vaccine basket for the country’s adult population.

How does Corbevax work?

Corbevax is a “recombinant protein sub-unit” vaccine, which means it is made up of a specific part of SARS-CoV-2, that is, the spike protein on the virus’s surface.

The spike protein allows the virus to enter cells so that it can replicate and cause disease. However, when just the spike protein is injected into the body, it is not as harmful as the virus itself, because the rest of the virus is missing.

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The body is expected to develop an immune response against the injected spike protein and, if and when the real virus attempts to infect, the body has an immune response ready, which will make it unlikely that the virus can make the victim seriously ill.

This technology itself is not new. It has been used for decades to make hepatitis B vaccines. However, Corbevax is among the first Covid-19 vaccines to use this platform.

Gaithersburg, Maryland-based Novavax too has developed a protein-based vaccine, which has been manufactured in India under licence by Serum Institute of India. This vaccine, named Covovax in India, received restricted emergency use authorisation for the 12-17 age group from DCGI last month.

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How was Corbevax made?

While Biological E, the manufacturer of Corbevax, is a Hyderabad-based biological products company, the beginnings of the vaccine can be traced to the National School of Tropical Medicine at the Baylor College of Medicine (BCM) in Houston, Texas. The school had been working on recombinant protein vaccines for coronaviruses SARS and MERS for a decade.

“We knew all the techniques required to produce a recombinant protein (vaccine) for coronaviruses at high levels of efficiency and integrity,” Dr Peter Hotez, Professor and Dean at the National School of Tropical Medicine had told The Indian Express earlier.

When the genetic sequence for SARS-CoV-2 was made available in February 2020, researchers at the school pulled out the sequence for the gene for the spike protein, and worked on cloning and engineering it. The gene was then put into yeast, so that it could manufacture and release copies of the protein.

“It’s actually similar to the production of beer. Instead of releasing alcohol, in this case, the yeast is releasing the recombinant protein,” Dr Hotez said.

The protein was then purified to remove any remnants of the yeast “to make it pristine”. The vaccine was then formulated using an adjuvant to better stimulate the immune response.

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Most of these ingredients are cheap and easy to find.

In August 2020, BCM transferred its production cell bank for this vaccine to Biological E, so that the Hyderabad-based company could take the candidate through trials.

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How is Corbevax different?

The Covid-19 vaccines manufactured by Pfizer and Moderna are mRNA vaccines; those made by AstraZeneca-Oxford (Covishield in India), Johnson & Johnson and Sputnik V are viral vector vaccines; and Covaxin, Sinovac-CoronaVac, and Sinopharm’s SARS-CoV-2 Vaccine-Vero Cell are inactivated vaccines.

Inactivated vaccines, which contain killed particles of the whole SARS-CoV-2 virus, seek to target the entire structure of the virus. On the other hand, Corbevax, like the mRNA and viral vector vaccines, targets only the spike protein, but in a different way.

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Viral vector and mRNA and vaccines use a code to induce human cells to make the spike proteins against which the body has to build immunity. “In this case (Corbevax), we’re actually giving the protein,” Dr Hotez said.

Like most other Covid-19 vaccines, Corbevax is administered in two doses.

First published on: 26-04-2022 at 08:26:36 pm
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