Childhood vaccinations are important because they protect children from contracting deadly diseases such as diphtheria, tetanus and polio. They also keep other children safe by decreasing or even eliminating the spread of dangerous diseases from child to child. A vaccine is a dead or attenuated (weakened) version of a virus. When children are exposed to a disease in vaccine form, their immune system detects the foreign particles as pathogenic and then produces antibodies to protect them from contracting the disease.