What is the basic principle behind vaccine development ? How do vaccines work ? What approaches were…

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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 ?

Ghissu Editorial · Accepted Answer

Vaccines work by presenting a safe antigen that builds immunological memory, so the body neutralises the real pathogen quickly. Indian manufacturers used every major platform for COVID-19, from inactivated Covaxin and vector-based Covishield to ZyCoV-D, the world's first approved human DNA vaccine.

**Introduction**

India gave over 220 crore COVID-19 vaccine doses, mostly home-made. The principle goes back to Edward Jenner's cowpox experiment of 1796: train immunity safely before infection.

**Basic Principle Behind Vaccine Development**

1. **Immunological memory**: A vaccine presents an antigen, or its code, so memory cells form without disease.
2. **Safety with immunogenicity**: The pathogen is weakened, killed or reduced to one protective part, such as the SARS-CoV-2 spike protein, and tested in phased trials before CDSCO approval.

**How Vaccines Work in the Body**

SKETCH: flow | From Jab to Protection
- Antigen enters
- Immune cells present it
- B and T cells activate
- Antibodies and killer cells
- Memory cells persist

1. **Faster response**: On real exposure, memory cells recognise and neutralise the pathogen within days, before disease sets in.
2. **Herd immunity**: High coverage breaks transmission, protecting infants and the immunocompromised.

**Approaches of Indian Manufacturers for COVID-19**

1. **Inactivated virus**: Bharat Biotech's Covaxin, with ICMR-NIV, used killed virus and an adjuvant.
2. **Viral vector**: Serum Institute's Covishield used the Oxford-AstraZeneca ChAdOx1 adenovirus, and iNCOVACC went intranasal.
3. **DNA**: Zydus Cadila's ZyCoV-D (2021) was the world's first approved human DNA vaccine, needle-free.
4. **Protein subunit**: Biological E's Corbevax used a yeast-grown receptor-binding domain.
5. **mRNA**: Gennova's GEMCOVAC (2022) was India's first mRNA vaccine, stable at 2 to 8 degrees Celsius.

**Way Forward**

1. **Ready platforms**: Keep mRNA and DNA platforms funded on the Mission COVID Suraksha model, with Biopharma SHAKTI (Budget 2026-27) expanding trial sites.

**Conclusion**

Vaccines build memory without disease, and Indian firms mastered every major platform within two years, sustaining India's role as the pharmacy of the world.

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 ?

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