Overview
This lecture covers the main types of vaccines currently in use, focusing on their mechanisms, advantages, disadvantages, and key differences.
Live Attenuated Vaccines
- Contain living organisms weakened via genetic manipulation or culture methods.
- Closely mimic actual infection, providing both cellular (T-cell) and humoral (B-cell) immunity.
- Typically require only one dose and give long-lasting immunity.
- Risk of infection in immunocompromised people and potential reversion to a pathogenic form.
- Can be spread to others but with a weakened organism.
Inactivated (Killed) Vaccines
- Use whole pathogens that have been killed by chemicals, heat, or radiation.
- Easier to store and transport; no risk of causing infection.
- Only induces humoral (B-cell) immunity, leading to weaker and shorter-lasting protection.
- Require multiple doses or series of injections for effectiveness.
- Safe for immunocompromised people.
Subunit Vaccines
- Use specific pieces (proteins, sugars) of the pathogen, not the whole organism.
- No risk of infection; generally require multiple doses.
- Includes recombinant vaccines (genetically engineered components) and virus-like particles (look like viruses but are not infectious).
Toxoid Vaccines
- Made from inactivated toxins produced by bacteria.
- Protect against the harmful effects of toxins, not the organism itself.
- Induce humoral immunity only; examples include vaccines for tetanus, diphtheria, and pertussis.
- Require periodic booster shots, often every ten years.
Conjugate Vaccines
- Combine pieces of pathogen (usually polysaccharide capsules) with proteins to enhance immune response, especially in children.
- Help provide effective immunity in populations less responsive to plain polysaccharide vaccines.
- Example: Pneumococcal conjugate vaccine.
Key Terms & Definitions
- Attenuated — Weakened form of a pathogen used in live vaccines.
- Humoral Immunity — Immune response via antibodies produced by B-cells.
- Cellular Immunity — Immune response involving T-cells.
- Toxoid — Inactivated toxin used to immunize against the toxin's effects, not the organism.
- Subunit Vaccine — Vaccine containing only pieces of the pathogen.
- Conjugate Vaccine — Vaccine combining a pathogen piece with a protein to boost immunity.
Action Items / Next Steps
- Review your class notes on vaccine types.
- Be familiar with examples for each vaccine type.
- Understand which vaccines are safe for immunocompromised individuals.