Corbevax is a “recombinant protein sub-unit” vaccine, which means it is made up of a specific part of SARS-CoV-2 — the spike protein on the virus’s surface.
The spike protein allows the virus to enter the cells in the body so that it can replicate and cause disease. However, when this protein alone is given to the body, it is not expected to be harmful as the rest of the virus is absent. The body is expected to develop an immune response against the injected spike protein. Therefore, when the real virus attempts to infect the body, it will already have an immune response ready that will make it unlikely for the person to fall severely ill.
Although this technology has been used for decades to make hepatitis B vaccines, Corbevax will be among the first Covid-19 vaccines to use this platform. Novavax has also developed a protein-based vaccine, which is still waiting for emergency use authorisation from various regulators.
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How Corbevax was made
While it is indigenously produced, Corbevax’s beginnings can be traced to the Baylor College of Medicine’s National School of Tropical Medicine. 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,” said Dr Peter Hotez, Professor and Dean at the School.
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.
After this, the protein was purified to remove any remnants of the yeast “to make it pristine”. Then, the vaccine was formulated using an adjuvant to better stimulate the immune response.
Most of these ingredients are cheap and easy to find.
In August, BCM transferred its production cell bank for this vaccine to Biological E, so that the Hyderabad-based company could take the candidate through trials. The vaccine has received approval for phase 3 trials, which the government expects will be over by July.
Biological E is also expected to scale up production for the world.
How Corbevax is different
Other Covid-19 vaccines approved so far are either mRNA vaccines (Pfizer and Moderna), viral vector vaccines (AstraZeneca-Oxford/Covishield, Johnson & Johnson and Sputnik V) or inactivated vaccines (Covaxin, Sinovac-CoronaVac and Sinopharm’s SARS-CoV-2 Vaccine–Vero Cell).
Inactivated vaccines, which include killed particles of the whole SARS-CoV-2 virus, attempt to target the entire structure of the virus. On the other hand, Corbevax, like the mRNA and viral vector Covid-19 vaccines, targets only the spike protein, but in a different way.
Viral vector and mRNA and vaccines use a code to induce our cells to make the spike proteins against which the body have to build immunity. “In this case (Corbevax), we’re actually giving the protein,” said Dr Hotez.
Like most other Covid-19 vaccines, Corbevax is administered in two doses. However, as it is made using a low-cost platform, it is also expected to be among the cheapest available in the country.
Why Corbevax matters
This is the first time the Indian government has placed an order for a vaccine that has not received emergency use authorisation, paying Rs 1,500 crore in advance to block an order that could vaccinate 15 crore Indian citizens. The Centre has provided major pre-clinical and clinical trial support towards the vaccine’s development, including a grant-in-aid of Rs 100 crore from the Department of Biotechnology.
A major reason for India placing such a big order is the difficulties it is facing in enhancing vaccine supplies. While the US, UK and the EU had made advance payments and at-risk investments into vaccines like Pfizer, AstraZeneca and Moderna, India waited until after its first two vaccines were approved before placing limited orders. Even after the government eased regulatory requirements for foreign vaccines, it did not receive a speedy response from companies like Pfizer and Moderna, their supplies already blocked through orders from other countries. India is currently in negotiations for a limited supply of Pfizer’s vaccine, and expecting to secure up to two billion doses of Covid vaccines by December this year. Given the ease with which it can be mass produced, Corbevax could make up a sizeable portion of this expected supply.
Biological E, the manufacturer of Corbevax
Biological E, headquartered in Hyderabad, was founded by Dr D V K Raju in 1953 as a biological products company that pioneered the production of heparin in India. By 1962, it forayed into the vaccines space, producing DPT vaccines on a large-scale. Today, it is among the major vaccine makers in India and, by its own claim, the “largest” tetanus vaccine producer in the world.
It has seven WHO-prequalified shots, including a five-in-one vaccine against diphtheria, tetanus, pertussis, hepatitis B and haemophilus influenza type-b infections. Its vaccines are supplied to over 100 countries and it has supplied more than two billion doses in the last 10 years alone.
Since 2013, the company has been under the management of Mahima Datla — the third generation of the founding family. During her time as managing director, the company has received WHO prequalification of its Japanese encephalitis, DTwP and Td as well as measles and rubella vaccines and also commenced commercial operations in the US.
A Covid-19 vaccination drive at a government school in Sarkhej. (Express Photo: Nirmal Harindran) 
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