A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms
of the microbe, its toxins or one of its surface proteins.
Vaccines work by stimulating our immune system to produce antibodies (substances produced by the body to
fight disease) without actually infecting us with the disease. Vaccines trigger the immune system to produce its own antibodies against disease, as though the body has been infected with it. This is called “active immunity”. If the vaccinated person
then comes into contact with the disease itself, their immune system will
recognize it and immediately produce the antibodies they need to fight it.