vaccines

• Pathogen


  Microorganism that causes disease
• Disease


  Illness affecting plants and animals
• Vaccine


  Substances containing disabled antigens of a particular disease, usually administered via injection, that stimulate the body to produce antibodies to provide immunity against that disease
• Antigen


  A protein on the surface of a substance (often a pathogen) that triggers an immune response
• White blood cell


  A type of cell found in blood that defends against infection
• Antibody


  A protein produced by the immune system in humans (and other animals) that attacks foreign organisms (antigens) that get into the body
• Phagocytosis


  When a white blood cell engulfs and digests a pathogen
• Primary infection


  The first time an organism becomes infected by a particular pathogen
• Herd immunity


  The indirect protection from an infectious disease that occurs when a population is immune either through vaccination or immunity developed through previous infection, making it difficult for the disease to spread from person to person
• Some diseases can be treated with antibiotics
• Vaccinations allow protection against specific diseases, but the level of protection depends on the amount of people vaccinated
• During the primary infection the antibodies slowly increase, peak at around ten days and then gradually decrease
• A second exposure to the same pathogen causes the white blood cells to respond quickly in order to produce lots of the relevant antibodies, which prevents infection