Corbevax Covid-19 Vaccine | 05 Jun 2021

Why in News

India has placed an advance order to block 300 million doses of a new Covid-19 vaccine, Corbevax.

Key Points

  • Corbevax:
    • About: It is India’s indigenous Covid-19 vaccine which is currently undergoing Phase 3 clinical trials.
    • Working:
      • It is a “recombinant protein sub-unit” vaccine.
        • It 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.
  • Difference between Corbevax and Other Covid-19 Vaccines:
    • They are either mRNA vaccines (Pfizer and Moderna), viral vector vaccines (Covishield and Sputnik V) or inactivated vaccines (Covaxin, Sinovac-CoronaVac and Sinopharm’s Vero Cell).
    • Viral vector and mRNA vaccines use a code to induce our cells to make the spike proteins against which the body has to build immunity.
      • In the case of Corbevax, protein itself is given.
      • mRNA vaccines work by using messenger RNA (mRNA), which is the molecule that essentially puts DNA instructions into action. Inside a cell, mRNA is used as a template to build a protein.
      • Viral vector vaccines use a modified version of a different virus (the vector) to deliver important instructions to our cells.
    • Inactivated vaccines include killed particles of the whole SARS-CoV-2 virus, attempting to target the entire structure of the virus.
      • Corbevax, like the mRNA and viral vector Covid-19 vaccines, targets only the spike protein, but in a different way.

Other Types of Vaccine

  • Live-attenuated Vaccines:
    • Live vaccines use a weakened (or attenuated) form of the germ that causes a disease.
    • Because these vaccines are so similar to the natural infection that they help prevent, they create a strong and long-lasting immune response.
    • The limitation of this approach is that these vaccines usually cannot be given to people with weakened immune systems.
    • Live vaccines are used against: Measles, mumps, rubella (MMR combined vaccine), Rotavirus, Smallpox among others.
  • Subunit, recombinant, polysaccharide, and conjugate Vaccines:
    • They use specific pieces of the germ - like its protein, sugar, or capsid (a casing around the germ). They give a very strong immune response.
    • They can also be used on people with weakened immune systems and long-term health problems.
    • These vaccines are used to protect against: Hib (Haemophilus influenzae type b) disease, Hepatitis B, HPV (Human papillomavirus), Pneumococcal disease among others.
  • Toxoid Vaccines:
    • Toxoid vaccines use a toxin made by the germ that causes a disease. Toxoid vaccines are used to protect against: Diphtheria, Tetanus.

Source: IE