In the last decade, parents in the whole world have come to believe that the risks associated to the use of vaccines are greater than the dangers of the diseases themselves. In the first minute of this clip, Professor Richard Dawkins and Dr. Michael Fitzpatrick explain why many parents were so easily dissuaded from vaccinating their kids. Their account is consistent with psychological research on decision making:
First, vaccines have been so effective at eradicating diseases that people no longer fret about them. Indeed, it has been a long time since we witnessed cases of measles, mumps or rubella (says Dr. Fitzpatrick). As a result, we wrongfully believe that the threat of these diseases is less impending, simply because we cannot recall anyone having them .
Second, vaccinating a child is scarier, because “it is a positive act” (says Dawkins), and people tend to “feel more regret for acts of commission (what they did) than for acts of omission (what they did not do)” [2, page 102]. Since many individuals are motivated to avoid regret , it is understandable why some parents chose to forgo vaccines for their children.
Fortunately, there is a way to counter this exaggerated fear of vaccines: by using icon arrays (see previous post), doctors and communicators can improve accuracy of risk perception, and ultimately provide decision advice. 
- Tversky, A. & Kahneman, D. (1992). Judgment under uncertainty: Heuristics and Biases. In Arkhes, H.R. & Hammond, K.R., Judgment and decision-making. Cambridge University Press: Cambridge, MA.
- Bazerman, M. (1998). Judgment in managerial decision making. New York: John Wiley & Sons.
- Galesic, M., Garcia-Retamero, R. & Gigerenzer, G. (2009). Using Icon Arrays to Communicate Medical Risks: Overcoming Low Numeracy. Health Psychology, 28, 2, 210–216.