Immunity (medical)
state of being insusceptible or resistant to a noxious agent or process / From Wikipedia, the free encyclopedia
Immunity is the ability of the body to defend itself from 'foreign bodies'. This means rejecting infections, clearing up dust which gets in the lungs, and killing cancer cells.
Immunity is of two types. Innate immunity protects the host against infection, but has no 'memory', and so gives no long-term immunity.
The second type is adaptive immunity, which does have a kind of 'memory'. It does give long-term protection against specific pathogens.
All animals, plants and fungi have some innate immunity. Vertebrates also have adaptive immunity.
People can be immunised from some diseases by having a vaccination (injection of some dead or weakened virus, or bacteria that causes the disease). Vaccination builds on the natural immune system to make a person resist certain diseases. By doing so, the body reacts more quickly to fight the virus/bacteria when it comes.