Vaccines

A vaccine is a biological preparation introduced into the body to stimulate active immunity against a specific disease.

Vaccination is a preventive method in which antigenic material is introduced into the body so that the immune system develops protection in advance. The material may contain weakened pathogens, killed pathogens, or their antigenic proteins, which trigger antibody formation without causing full disease under normal conditions.

When the body encounters the vaccine, the immune system responds by producing specific antibodies and forming memory B-cells and T-cells. These memory cells remain prepared and respond quickly if the same pathogen enters the body again, giving faster and stronger protection during later exposure.

1. Vaccine material enters the body.
2. The immune system recognises it as a foreign antigen.
3. Antibodies are produced against that antigen.
4. Memory B-cells and memory T-cells are formed.
5. On future infection, the pathogen is recognised rapidly.
6. A quick and strong immune response prevents or reduces disease severity.

• A vaccine is a biological preparation introduced into the body to stimulate active immunity.
• Vaccines contain weakened, killed pathogens or their antigenic proteins that induce antibody production.
• Vaccination also produces memory B-cells and T-cells, providing long-term protection against future infections.
• Modern vaccines include genetically engineered second- and third-generation vaccines developed using biotechnology.