Vaccine safety studies are intended to prove that the risk of a vaccine is less than the risk of the disease. However, the vaccine safety studies for the diphtheria, tetanus, and pertussis (DTaP); polio (IPV); Haemophilus influenzae type b (Hib); varicella (chicken pox); hepatitis B; and measles, mumps, and rubella (MMR) vaccines do not have the statistical power to detect risk levels as low as the 10 diseases they target.