Q. What is the basic principle behind vaccine development? How do vaccines work? What approaches were adopted by the Indian vaccine manufacturers to produce COVID-19 vaccines ?

Model Answer: 

Vaccines are biological preparations providing active acquired immunity against specific infectious diseases by training the body’s immune system to recognize and combat pathogens.

1. Basic Principle and Working Mechanism

• Basic Principle (Mimicry): The core principle is exposing the body to a harmless pathogen fragment (antigen) to mimic an infection, stimulating protective immunity without causing the actual disease.
• Working Mechanism:
  1. Antigen Presentation: Specialized immune cells (macrophages/dendritic cells) detect the vaccine antigen and present it to the immune system.
  2. Antibody Production: B-lymphocytes are triggered to produce specific, neutralizing antibodies tailored against the identified antigen.
  3. Cellular Response: Helper T-cells coordinate the immune response, while Cytotoxic T-cells destroy infected cells.
  4. Immunological Memory: Memory B-cells and T-cells remain dormant post-vaccination, ensuring a rapid, robust defense upon future natural pathogen exposure.

2. Approaches by Indian COVID-19 Vaccine Manufacturers

Indian manufacturers utilized diverse, cutting-edge technological platforms, supported by government initiatives like Mission COVID Suraksha:

1. Viral Vector Platform: Uses a modified, harmless chimpanzee adenovirus to deliver the SARS-CoV-2 spike protein gene (Covishield by Serum Institute of India).
2. Whole-Virion Inactivated: Uses chemically deactivated SARS-CoV-2 virus, unable to replicate but fully capable of triggering immunity (Covaxin by Bharat Biotech).
3. Plasmid DNA Technology: Developed the world’s first human DNA vaccine, introducing engineered plasmids to produce spike proteins (ZyCoV-D by Zydus Cadila).
4. Protein Subunit: Uses harmless, purified fragments of the viral spike protein grown in laboratory settings (Corbevax by Biological E; Covovax by SII).
5. mRNA Technology: Utilizes synthetic messenger RNA to instruct human cells to manufacture spike proteins (GEMCOVAC-19 by Gennova Biopharmaceuticals).
6. Intranasal Delivery: Targets mucosal immunity directly in the respiratory tract using a recombinant adenovirus (iNCOVACC by Bharat Biotech).

By leveraging these diverse platforms, India cemented its position as a global biomanufacturing hub, ensuring both domestic health security and vital contributions to global vaccine equity.