How Bharat Biotech’s Covaxin Vaccine Works
Indian company Bharat Biotech, in collaboration with the National Institute of Virology and the Indian Council of Medical Research, has developed an inactivated coronavirus vaccine called Covaxin. India approved the emergency vaccine on Jan. 3, despite no published Phase 3 data showing the vaccine is safe and effective.
A coronavirus vaccine
Covaxin teaches the immune system to make antibodies against the SARS-CoV-2 coronavirus. The antibodies bind to viral proteins, such as the so-called spike proteins, which examine their surface.
To make Covaxin, Bharat Biotech used a sample of the coronavirus that was isolated by India's National Institute of Virology.
Kill the virus
After the researchers made large amounts of coronavirus, they doused them with a chemical called beta-propiolactone. The compound deactivated the coronaviruses by binding to their genes. The inactivated corona viruses could no longer replicate. But their proteins, including the tip, remained intact.
The researchers then peeled off the inactivated viruses and mixed them with a tiny amount of an aluminum-based compound called an adjuvant. Adjuvants stimulate the immune system to increase its response to a vaccine.
Inactivated viruses have been used for over a century. Jonas Salk used them to make his polio vaccine in the 1950s and they are the basis for vaccines against other diseases such as rabies and hepatitis A.
Invitation to the immune response
Since the coronaviruses in Covaxin are dead, they can be injected into the arm without causing Covid-19. In the body, some of the inactivated viruses are swallowed by a type of immune cell called an antigen-presenting cell.
Present
Virus protein
Fragments
Present
Virus protein
Fragments
Present
Virus protein
Fragments
The antigen presenting cell tears up the coronavirus and shows some of its fragments on its surface. A so-called helper T cell can detect the fragment. When 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.
Making Antibodies
Another type of immune cell called a B cell can also encounter the inactivated coronavirus. B cells have surface proteins in a variety of shapes, and some may be the right shape to attach to the coronavirus. When a B-cell locks into place, it can draw in some or all of the virus and present coronavirus fragments on its surface.
A helper T cell activated against the coronavirus can bind to the same fragment. In this case, the B cell is also activated. It multiplies and releases antibodies that are the same shape as their surface proteins.
Matching
Surface proteins
Matching
Surface proteins
Matching
Surface proteins
Matching
Surface proteins
Matching
Surface proteins
Matching
Surface proteins
Matching
surface
Proteins
Matching
surface
Proteins
Matching
surface
Proteins
Matching
Surface proteins
Matching
Surface proteins
Matching
Surface proteins
Stop the virus
Once vaccinated with Covaxin, the immune system can respond to infection with live coronaviruses. B cells produce antibodies that adhere to the invaders. Antibodies that target the spike protein can prevent the virus from entering cells. Other types of antibodies can block the virus in different ways.
Memory of the virus
Covaxin is tested in two doses four weeks apart.
Second dose
28 days later
Second dose
28 days later
Second dose
28 days later
If Bharat Biotech's Phase 3 clinical trial shows Covaxin protects people from Covid-19, researchers will have to watch for months to see how long that protection lasts. It is possible that antibody levels may drop, but the immune system also contains special cells called memory B cells that can hold information about the coronavirus for years or even decades.
Vaccination schedule
June 2020 Covaxin is the first coronavirus vaccine made in India to be approved for clinical trials.
July A phase 1/2 clinical trial will begin with 755 participants.
September Results from monkey and hamster studies show that Covaxin offers protection against infection.
23rd October The company announces a phase 3 study with up to 25,800 participants.
A dose of Covaxin in Ahmedabad, India.Amit Dave / Reuters
December Covaxin's Phase 1/2 study shows the vaccine produces antibodies to the coronavirus without causing serious side effects.
December 22 Bharat Biotech announces a partnership with Ocugen of Pennsylvania to develop Covaxin for the US market.
January 3, 2021 The Government of India is granting Covaxin an emergency approval, although no phase 3 data has been released to show the vaccine is safe and effective. The country also approves a vaccine from Oxford University and AstraZeneca.
Sources: National Center for Information on Biotechnology; Science; The lancet; Lynda Coughlan, University of Maryland Medical School; Jenna Guthmiller, University of Chicago.
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