Most people feel less at risk when it is their choice. Parents want control A related outrage factor deals with control. The perceived risk is much less when a person is in control of their own actions, as opposed to being controlled by others. Terracciano said, for example, the composition of the vaccine is not controlled by the parent and therefore, they feel at risk. Natural risks seem to be more acceptable then man-made risks.
Familiarity also plays a part because familiar risks and surroundings diminish outrage.
Childhood vaccines are familiar to most parents, however, new vaccines or situations involving vaccines may be perceived as exotic, according to Teracciano. Memorable incidents and images of risk exacerbate outrage, and vaccination is usually a memorable experience. Many parents don't recognize many of the vaccine-preventable diseases and don't have a memory of them, yet they remember their child crying after receiving the first series of immunizations. An event or risk that is unexplainable or explainable only by experts is less acceptable than a risk that is generally understood. Components of this theory include uncertainty, and expert disagreement which all confuse the parents because the so-called experts now include people other than physicians.