Vaccination Notes

Why Is Vaccination Used?

1. Infectious diseases trigger immune responses that take time.
   1. When a pathogen enters the body for the first time, the immune response is slow.
   2. Symptoms develop while the immune system learns how to respond.
2. Vaccination reduces or prevents this delay
   1. It exposes the immune system to pathogen antigens in advance.
   2. Protection occurs before real infection happens.

How Does Vaccination Work?

1. Vaccination introduces antigens without causing disease
   1. A vaccine contains antigens, instead of a fully functioning pathogen.
   2. These antigens may be:
      1. Weakened (attenuated) forms of a pathogen.
      2. Inactivated (killed) pathogens.
      3. Specific pathogen fragments, usually surface proteins.
      4. Genetic instructions that allow cells to produce a harmless antigen.
2. Antigens Are Recognized As Foreign
   1. Antigens are detected by white blood cells in the immune system.
   2. Specialized immune cells display antigens to lymphocytes, signalling a potential threat.
3. Lymphocytes Produce Specific Antibodies
   1. B lymphocytes produce antibodies that bind to a specific antigen.
   2. Each antibody has a unique shape that matches only one antigen.
   3. This specificity ensures the response targets the correct pathogen.
4. Memory Cells Are Formed
   1. Some activated lymphocytes differentiate into memory cells.
   2. Memory cells remain in the body long term.
   3. They enable a faster and stronger secondary immune response.
5. Rapid Secondary Response Prevents Disease
   1. If the real pathogen enters the body later:
      1. Memory cells recognize the antigen immediately.
      2. Antibodies are produced rapidly in high concentration.
      3. The pathogen is eliminated before symptoms develop.

Why Do Some Diseases Disappear And Others Persist?

1. Eradication occurs when transmission stops completely.
2. A disease is eradicated when it no longer exists in the human population.
3. This requires:
   1. Effective vaccines
   2. Sustained high vaccination coverage worldwide
   3. No non-human reservoirs
4. Herd immunity limits disease spread
   1. When most individuals are immune, pathogens struggle to spread.
   2. Transmission chains are broken.
   3. Unvaccinated individuals receive indirect protection.
5. Some diseases are difficult to eradicate, which occurs when they:
   1. Have animal reservoirs
   2. Mutate rapidly
   3. Experience reduced vaccination uptake, allowing diseases to re-emerge.

Definition

Herd immunity

Protection of a population when a sufficiently high proportion is immune, reducing disease transmission.

What Are The Main Types Of Vaccines?

What Are The Benefits And Risks Of Vaccination?

1. Benefits
   1. Prevents serious infectious diseases.
   2. Reduces disease transmission.
   3. Protects vulnerable individuals.
   4. Enables disease eradication.
2. Risks
   1. Mild side effects such as soreness or fever.
   2. Very rare allergic reactions.

Why Is Vaccination Essential For Public Health?

1. Prevention of outbreaks
   1. Maintains herd immunity.
   2. Prevents rapid spread in communities.
2. Cost-effective healthcare
   1. Reduces hospital admissions.
   2. Lowers long-term healthcare costs.
3. Protection of vulnerable groups
   1. Infants.
   2. Elderly individuals.
   3. Immunocompromised patients.