%0 Journal Article %T Individual freedom versus collective responsibility: an economic epidemiology perspective %A M Zia Sadique %J Emerging Themes in Epidemiology %D 2006 %I BioMed Central %R 10.1186/1742-7622-3-12 %X Immunisation represents a classic case of social dilemma: a conflict of interest between the private gains of individuals and the collective gains of a society. An individual's self-interest and choice often leads to a vaccination uptake rate less than the social optimum as individuals do not take into account the benefit to others [1]. Conventional wisdom generally favours public intervention in order to produce a socially warranted level of vaccination. This line of argument is primarily based on the externality associated with individual decisions, since individuals are presumed to make choices on the basis of their own welfare gains, without considering the full social impact of their decisions. As the benefits to society are larger than the sum of those to individuals, public policy measures aim to increase demand closer to the social optimum by subsidising the vaccine (many countries provide vaccines free of charge) or through compulsory vaccination, although such a policy is almost always partial. Individuals with religious, medical or social reasons are often exempted. There is, however, controversy over the effectiveness of public intervention compared to the free choice outcome [1-3], and it is the intention of this article to address this issue.Vaccination decisions are made under imperfect information, which means an individual's assessment of the risks and benefits of vaccination is often inaccurate. But even if individuals had perfect information regarding the cost and benefits of vaccination, the free choice outcome would still be different from the social outcome due to the 'free rider' problem associated with vaccination. The changes in risk of infection tend to induce changes in activities that put the individual at risk, which in turn alter the dynamics of disease transmission. There is a feedback mechanism between infection rate and rational response, but the classic models of infectious disease have not incorporated such endogenous behavioural r %U http://www.ete-online.com/content/3/1/12