How Bharat Biotech’s Covaxin Vaccine Works

The Indian company Bharat Biotech has partnered with the National Institute of Virology and the Indian Council of Medical Research to develop an inactivated coronavirus vaccine called Covaxin. India approved the vaccine for emergency use on January 3, despite a lack of published Phase 3 data indicating that the vaccine is safe and effective.

A vaccine made from coronaviruses

Covaxin works by teaching the immune system to make antibodies against the SARS-CoV-2 coronavirus. The antibodies attach to viral proteins, such as the so-called vein proteins that study at the surface.

To create Covaxin, Bharat Biotech used a sample of the coronavirus isolated by India’s National Institute of Virology.

Killing the virus

After the researchers produced large stocks of coronaviruses, they used them with a chemical called beta-propiolactone. The compound eliminated the coronaviruses by binding to their genes. The inactivated coronaviruses could not be repeated. But their proteins, including veins, remained intact.

The researchers then extract the inactivated viruses and mix them with a small amount of an aluminum compound called an additive. Aids stimulate the immune system to increase the response to a vaccine.

Activated viruses have been in use for over a century. Jonas Salk used it to create his polio vaccine in the 1950s, and it is the basis for vaccines against other diseases, including rabies and hepatitis A.

Request an immune response

Because the coronaviruses in Covaxin are dead, they can be injected into the arm without causing Covid-19. Some of the inactivated viruses are swallowed into the body by a type of immune cell called an antigen-presenting cell.

The antigen-presenting cell tears the coronavirus apart and displays some of its fragments on the surface. A so-called helper T cell can detect the fragment. If the fragment fits into one of its surface proteins, the T cell is activated and can help recruit other immune cells to respond to the vaccine.

Make antibodies

Another type of immune cell, called a B cell, can also encounter the inactivated coronavirus. B cells have surface proteins in a wide variety of forms, and some may have the right form to attach to the coronavirus. If a B cell locks up, it can pull a portion of the virus inside or present coronavirus fragments on the surface.

A helper T cell activated against the coronavirus can attach to the same fragment. If this happens, the B cell is also activated. It multiplies and releases antibodies that have the same shape as their surface proteins.

Stop the virus

Once vaccinated with Covaxin, the immune system can respond to a live coronavirus infection. B cells produce antibodies that attach to the invaders. Antibodies that target the peak protein can prevent the virus from entering cells. Other types of antibodies can block the virus in other ways.

Remember the virus

Covaxin is tested in two doses, four weeks apart.

If the Phase 3 clinical trial of Bharat Biotech shows that Covaxin protects people against Covid-19, researchers will have to observe it for months to see how long the protection lasts. The level of antibodies will possibly drop, but the immune system also contains special cells called memory B cells, which can retain information about the coronavirus for years or even decades.

Vaccination timeline

June 2020 Covaxin is the first coronavirus vaccine created in India to be approved for clinical trials.

July A Phase 1/2 clinical trial begins with 755 participants.

September Results from monkey and hamster studies show that Covaxin provides protection against infection.

October 23 The company announce a phase 3 trial with up to 25,800 participants.

December Phase 1/2 study of Covaxin shows that the vaccine produces antibodies against the coronavirus without causing any serious side effects.

December 22 Bharat Biotech announces partnership with Ocugen in Pennsylvania to develop Covaxin for US market.

January 3, 2021 The Indian government has granted Covaxin emergency authorization, despite the fact that no Phase 3 data are being released showing that the vaccine is safe and effective. The country also authorizes a vaccine made by the University of Oxford and AstraZeneca.

Sources: National Center for Biotechnology Information; Science; The Lancet; Lynda Coughlan, University of Maryland School of Medicine; Jenna Guthmiller, University of Chicago.

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