Lecture Notes: Types of Vaccines

Overview

• Vaccines are biological preparations providing acquired immunity to a particular disease.
• This lecture focuses on different types of vaccines currently in use.
• Future vaccines may not be covered in this discussion.

Live Attenuated Vaccines

• Definition: Use of living pathogenic organisms that have been weakened (attenuated).
  • Weakened through genetic manipulation or by growing in unfavorable conditions.
• Pros:
  • Mimics actual infection, providing lifelong immunity.
  • Provides both cellular (T-cells) and humoral (B-cells) immunity.
  • Often requires only one dose.
  • Transmission to contacts possible, but weakened.
• Cons:
  • Risky for immunocompromised individuals.
  • Possibility of back mutation to a pathogenic form.
  • Importance of herd immunity as some individuals can't be vaccinated.

Inactivated (Killed) Vaccines

• Definition: Pathogen is killed or inactivated (radiation, heat, chemicals).
• Pros:
  • Ease of storage and transport; no refrigeration needed.
  • No risk of infection from dead organism.
• Cons:
  • Provides weaker immunity, only humoral.
  • Requires a series of injections, not just one.
  • Dr. Oh uses different terminology for boosters (toxoid vaccines).

Subunit Vaccines

• Definition: Use of pieces of the pathogen instead of the whole organism.
• Process: Immune system recognizes parts like hair, eyes, ears of the pathogen.
• Types:
  • Recombinant vaccines (genetic modification).
  • Virus-like particles (VLPs) mimicking virus exterior without infection risk.
• Cons:
  • Multiple doses needed for full efficacy.

Toxoid Vaccines

• Definition: Protect against toxins produced by bacteria rather than the organism itself.
• Examples: Botulism, diphtheria, pertussis, tetanus.
• Usage:
  • Provides immunity against toxins, not the bacteria.
  • Often referred to as booster shots (every ten years).

Conjugate Vaccines

• Purpose: Enhances children's immune response to polysaccharide-coated bacteria.
• Process: Proteins are added to polysaccharides, improving immune response.
• Examples: Pneumovax (streptococcus pneumoniae), important for children but used in adults.

Conclusion

• These represent the major classes and types of vaccines.
• Each vaccine type has specific uses, advantages, and limitations.
• Important to understand the differences for application and public health strategies.