Whether or not it is stated, some form of theory is the basis of all prevention interventions. Theory provides a background for behavior change, and is also helpful in assessing whether an intervention is appropriate for a specific target group. It is a tool that can have an important influence on HIV-prevention programs.
Informal theory is hands-on knowledge about what works.
This comes from knowing the target population, having ideas about what determines client behaviors, and knowing their strengths and needs as individuals and as a community. Formal theory is made up of principles and methods about prevention and behavior that have already proved useful in some areas of disease prevention and behavior change. Using theories to design or adapt HIV prevention interventions can help improve programs, thus saving valuable time and resources. Some of the most widely known theories are presented below. These theories are not mutually exclusive, and can work together to guide effective programs.