Immunology and Vaccination Overview

Study Notes

Immune Response and Immunization

Immunized individuals experience a faster and stronger immune response compared to unimmunized individuals.
Immunization helps halt infectious agent spread through herd immunity, protecting both the individual and the community.
A significant illness-causing organism is a prime candidate for vaccine development.

Achievements of Immunization Programs

Protection against diseases such as rabies and tetanus.
Control of measles, mumps, rubella, varicella zoster, influenza, and rotavirus.
Global elimination of wild-type poliomyelitis, smallpox eradication.
Reduction in cancer risks associated with human papillomavirus (HPV) and hepatitis B virus (HBV).
Vaccine-preventable diseases still occur due to limited access and high costs in developing countries.

Types of Vaccines

Live Attenuated Vaccines (LAV)
Inactivated Vaccines
Component Vaccines (subunit vaccines)
Toxoid Vaccines
Naked DNA Vaccines
mRNA Vaccines

Live Attenuated Vaccines (LAV)

Derived from modified organisms (viruses or bacteria) made less virulent, enabling replication in the host without severe disease.
Simulates natural infections, resulting in comprehensive immune responses (humoral, cellular, and memory).
Examples: oral polio vaccine, measles, rotavirus, BCG vaccine for tuberculosis.

Preparation of LAV

Avirulent or attenuated organisms are utilized, which have reduced ability to cause illness.
Attenuation methods include:
- Growth under non-physiological conditions.
- Serial passage through tissue cultures to select less virulent strains.
- Genetic engineering to inactivate virulence genes.
- Recombinant vector vaccines where a gene insert leads to an immune response.

Advantages of LAV

Efficient and long-lasting immunity.
Immune response mimics natural infections.
Produces IgA at infection entry points.
Stimulates strong cell-mediated immunity.

Disadvantages of LAV

Potential risk of reversion to virulence.
Requires careful storage and handling due to limited shelf life.
Possible interference with co-infecting viruses.
Not suitable for immunocompromised individuals or pregnant women.

Inactivated Vaccines

Comprised of killed organisms that can no longer reproduce, aimed at eliciting an antibody immune response.

Preparation of Inactivated Vaccines

Killed through chemicals (like formalin) or physical methods (irradiation or heat).
Adjuvants such as aluminum hydroxide enhance immunogenicity.
Examples: Rabies, Influenza, Polio (Salk), Hepatitis A vaccines (killed viral) and Cholera, Q fever vaccines (killed bacterial).

Advantages of Inactivated Vaccines

No risk of reverting to virulence.
Safe for immunocompromised patients and during pregnancy.

Disadvantages of Inactivated Vaccines

Generally provide brief immunity, requiring boosters for continued effectiveness.
Primarily induce humoral immunity; cell-mediated responses tend to be weak.
Local IgA response at entry points is not elicited.
Higher doses may be necessary to produce adequate immunity.

Description

This quiz covers the immune response and the significance of immunization. Learn about the achievements of immunization programs and the various types of vaccines available. Test your knowledge on how vaccines protect both individuals and communities from infectious diseases.