Vaccinations are life-saving medical tools recommended and used for the prevention of dangerous and deadly diseases. Vaccines work by introducing controlled and weakened infections into the body, encouraging the immune system to create natural antibodies that will defend the body against possible future infections. Although children are subject to the most complex vaccination schedule, immunization recommendations continue into adulthood to include an annual flu vaccination, periodic tetanus and diphtheria vaccinations, varicella vaccinations, and other risk-based vaccines.