====== Vaccine Development ======

[[Vaccine]]s are biological preparations that stimulate the [[immune system]] to recognize and fight infectious [[agent]]s, without causing [[disease]]. The goal is to induce **protective immunity** and **herd immunity**.

===== 🧪 Phases of Vaccine Development =====

  - **Exploratory Phase**: Identification of potential antigens
  - **Preclinical Testing**: Animal models to test the [[immune response]]
  - **Clinical Trials**:
    - *Phase I*: Safety and dose
    - *Phase II*: [[Immunogenicity]] and safety
    - *Phase III*: Efficacy and rare side effects
    - *Phase IV*: Post-marketing surveillance
  - **Regulatory Review** (FDA, EMA, etc.)
  - **Manufacturing and Distribution**

===== 🔬 Types of Vaccines =====

^ Type                        ^ Example                       ^ Notes                                             ^
| **Live attenuated**         | MMR, Yellow Fever             | Strong immunity, not for immunocompromised       |
| **Inactivated**             | Polio (IPV), Hepatitis A      | Safer but may require boosters                   |
| **Subunit / Recombinant**   | HPV, Hepatitis B              | Specific antigens only                           |
| **Toxoid**                  | Tetanus, Diphtheria           | Inactivated toxins                               |
| **Viral vector**            | J&J COVID-19, AstraZeneca     | Delivers antigen via harmless virus              |
| **[[mRNA]]-based**              | Pfizer-BioNTech, Moderna      | No virus; fast to design and produce             |

===== 🧠 How Vaccines Work =====

  - Antigen is introduced into the body
  - Innate immune response is triggered
  - Antigen-presenting cells activate **T and B lymphocytes**
  - **Memory cells** are formed
  - Upon future infection, the response is **rapid and stronger**

===== ⚙️ Modern Innovations =====

  * **mRNA vaccines** (e.g., COVID-19)
  * **Self-amplifying RNA (saRNA)**
  * **Nanoparticle carriers**
  * **Universal vaccines** (e.g., flu)
  * **[[Cancer vaccine]]s** (personalized neoantigen therapy)

===== ⚠️ Challenges in Development =====

  - Antigen variability (e.g., influenza)
  - Logistics and cold chain requirements
  - Public vaccine hesitancy
  - Rare adverse events
  - Equitable global access

===== 🌍 Impact of Vaccines =====

  * Eradication of smallpox
  * Near-eradication of polio
  * Major reductions in childhood mortality
  * Crucial role in pandemic response (e.g., COVID-19)

===== 🧾 Summary =====

Vaccine development is a multi-phase, interdisciplinary process. With tools like **mRNA**, **nanotechnology**, and **personalized immunotherapy**, the field is evolving rapidly to address both **infectious and non-infectious** diseases.