Vaccination Principles

Basics & Immunity - Vaccine 101 Kickstart

• Vaccine: Biological agent providing active acquired immunity.

• Vaccination: Administering a vaccine.

• Immunization: Process of becoming protected against disease.

• Active Immunity: Body produces its own antibodies.

  • Natural: Post-infection (e.g., Measles). Long-lasting.
  • Artificial: Post-vaccination (e.g., MMR vaccine). Long-lasting.

• Passive Immunity: Pre-formed antibodies received.

  • Natural: Maternal (placenta, breast milk). Short-term.
  • Artificial: Immunoglobulin administration (e.g., Tetanus Immunoglobulin). Immediate, short-term.

• Immune Response to Vaccines:

  • Primary: Slow onset, lower Ab levels (IgM → IgG).
  • Secondary (Booster): Rapid, ↑↑ high Ab levels (IgG), memory.

⭐ Artificially acquired passive immunity provides immediate but temporary protection (e.g., Tetanus Immunoglobulin).

Vaccine Varieties - The Immunization Arsenal

📌 LIVE vaccines mnemonic: 'BOY, This Real MMR Vaccine is Scary' (BCG, OPV, Yellow Fever, Typhoid oral, Rota, MMR, Varicella, Influenza nasal, Sabin).

Live attenuated vaccines: robust, long-lasting immunity, often lifelong with one dose, mimic natural infection.

Delivery & Timelines - Shot Clock Science

• Routes & Examples:
  • IM: Hep B, DPT, IPV, PCV (Deltoid, Thigh)
  • SC: MMR, Varicella, JE (Thigh, Upper arm)
  • ID: BCG (L. Upper arm), Rabies (updated regimen)
  • Oral: OPV, Rotavirus
• 
• Scheduling Principles:
  • Simultaneous: Most vaccines, different sites.
  • Intervals:
    • Live-Live (if not same day): Min. 4 weeks.
    • Live-Inactivated: Any interval.
    • Inactivated-Inactivated: Any interval (often 4 weeks for same antigen).
• NIS India: Vital public health tool. Key vaccines: BCG, OPV, Hep B, Pentavalent, IPV, Rota, MMR, JE.
• Catch-up: Give missed doses ASAP per age/interval guidelines. No restart needed for most.

⭐ Most live vaccines can be given simultaneously. If not, a minimum interval of 4 weeks is required between two live vaccines_

Efficacy, Safety & Issues - Guarding the Guards

• Herd Immunity: Indirect protection for unvaccinated when many are immune; vital for community.
• Vaccine Performance:
  • Efficacy: Protection in ideal trial conditions.
  • Effectiveness: Protection in real-world settings.
• Adverse Events Following Immunization (AEFIs):
  • Common: Local (pain, redness), systemic (fever, malaise).
  • Serious: Rare (e.g., anaphylaxis, GBS); mandatory reporting.
• Contraindications:
  • General: Prior anaphylaxis to vaccine/component.
  • Live vaccines: Severe immunodeficiency, pregnancy (generally).
• Cold Chain: System for vaccine storage/transport at +2°C to +8°C.

  ⭐ The cold chain is critical for maintaining vaccine potency; most vaccines are stored between +2°C and +8°C, and freeze-sensitive vaccines (like DPT, TT, Hep B) must never be frozen.

High‑Yield Points - ⚡ Biggest Takeaways

• Live vaccines (MMR, OPV): long immunity; C/I in immunodeficiency & pregnancy.
• Killed vaccines (IPV, Rabies): multiple doses; safer for immunocompromised.
• Toxoids (Tetanus, Diphtheria): immunity against bacterial toxins.
• Cold chain: OPV (most heat-sensitive); Hep B, DPT, TT (freeze-sensitive).
• Minimum interval for two live vaccines (if not simultaneous): 4 weeks.
• Adjuvants (e.g., Alum) boost immunogenicity of killed/subunit vaccines.
• Anaphylaxis post-vaccination: treat with adrenaline.