Vaccines are biological preparations that teaches the body how to fight against a particular disease by generating an immune response. A vaccine typically contains a component 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.
More than 20 infectious diseases are now vaccine preventable. Infectious diseases like polio and diphtheria are now rarely reported due to widespread vaccination against these diseases in many settings of the world. If a child is not vaccinated against vaccine preventable diseases, severe illness or even death may occur.