Immunisation

The Process of Immunisation:

• A vaccine is created from an inactive or dead form of a pathogen, or sometimes just the antigens from the pathogen.
• The inactive pathogen is injected into the body.
  • This pathogen cannot cause disease because it is inactive, but it still contains the antigens that the immune system can recognize.

Body's Immune Response:

• The antigens from the inactive pathogen stimulate the body's specific immune system.
• Lymphocytes (a type of white blood cell) recognize the antigens as foreign and trigger an immune response.
  • Antibodies are produced to fight off the pathogen.
  • Memory lymphocytes are also created. These cells "remember" the pathogen and can produce antibodies quickly if the body is exposed to the real pathogen in the future.

Advantages of Immunisation:

• Prevents Illness: Immunisation helps protect individuals from serious diseases by preparing the immune system to fight the infection if it occurs.
• Herd Immunity: When a large proportion of a population is immunised, it becomes harder for a disease to spread. This is known as herd immunity, and it helps protect people who cannot be vaccinated (e.g., newborns or people with weak immune systems).
• Cost-Effective: Immunisation programs are often cheaper in the long run than treating people who get sick with preventable diseases.

Disadvantages of Immunisation:

• Side Effects: Some people may experience mild side effects from vaccines, such as a sore arm, fever, or fatigue. Serious side effects are rare but can occur.
• Not Always 100% Effective: Some vaccines may not provide complete immunity in all individuals. In these cases, the vaccinated person might still get the disease but often with milder symptoms.
• Allergic Reactions: In rare cases, people can have an allergic reaction to a vaccine component.

Herd Immunity:

• Definition: Herd immunity occurs when a high enough percentage of a population is vaccinated that the spread of the disease is greatly reduced, protecting those who are unvaccinated or vulnerable.
• How It Works: If enough people are immune to a disease, there are fewer people for the pathogen to infect. This reduces the overall spread of the disease.
• Importance: Herd immunity is essential for protecting individuals who cannot be vaccinated, such as infants, elderly people, or those with weakened immune systems.

Summary:

Pros	Cons
Some diseases have been virtually wiped out of immunisation programmes (eg. Small pox) Big outbreaks of diseases (epidemics) can be prevented if people are immunised. Even people not immunised they are less likely to catch the disease as there are fewer people to pass it on ('herd immunity')	Doesn't always give you immunity Bad reactions which are rare (eg. Swelling/fevers)