In recent years, individualized and medically supervised prevention has received relatively little attention from health policy makers. Yet it encompasses important activities carried out daily in clinical practice, primarily by general practitioners: vaccinations, screenings, health and dietary counseling, and so on. These procedures and expenditures (referred to as “hidden”) are estimated to be three times greater than the budgets allocated to prevention in preventive medicine and screening (such as occupational medicine, school health, etc.), for major public health programs (alcohol, tobacco, accidents, etc.), and various other initiatives such as occupational risk prevention or health surveillance (classified as “visible” expenditures). In total, prevention-related budgets amounted to 10 billion euros in 2003, or approximately 7% of current health expenditures: two-thirds “hidden” and one-third “visible.” Furthermore, vaccination has gradually become a routine practice. Several childhood infectious diseases have virtually disappeared thanks to vaccination policies, thereby erasing the clinical reality of these diseases from the collective memory. Nevertheless, the controversy surrounding the hepatitis B vaccine has contributed to undermining the credibility not only of this specific immunization but also of vaccines as a whole. This phenomenon has been accurately measured by various Health Barometers, both in the general population and among general practitioners. Finally, the absence of a proactive vaccination policy over the past twenty years has been exacerbated by successive waves of decentralization (at the departmental level in the 1980s) and recentralization (at the national level in the 2000s), leading to confusion in decision-making and organization among local healthcare providers. It was therefore particularly interesting to track the evolution of French people’s opinions, attitudes, and behaviors in this area of intervention, which remains essential to public health.[chapter introduction]