There are many reasons for this but one of the most dangerous vaccine ingredients appears to the vaccine adjuvants. Vaccine adjuvants are chemical substances which are supposed to enhance the immune response to the vaccine. There are several types of adjuvants. Some of the most common adjuvants include aluminium hydroxide, aluminium phosphate and calcium phosphate. Veterinarian Patricia Jordan, states that the World Health Organization named aluminum hydroxide, a component of most of the currently used veterinary vaccines, a grade 3 out of 4 carcinogen, with 4 being the most carcinogenic.