**6.3. Epidemiological studies**

Up to 2008, epidemiological studies did not support the hypothesis for the use of prophylactic antibiotics for medical procedures as a preventive method against IE. Case-control studies indicated that most IE events occurred independently of medical interventions and of the administration of antibiotic prophylaxis. A further argument was that despite the universal application of antibiotic prophylaxis, the incidence of IE and its associated mortality had not varied over decades [5].

In 2008, cessation of the NICE recommendation for antibiotic prophylaxis introduced a new epidemiological context into the study of IE, and analysis will serve to establish reliable conclusions in its area of influence. Implementation of the NICE guideline in England provides an opportunity for retrospective studies to investigate the comparative effect of antibiotic prophylaxis versus no prophylaxis on the incidence of IE.

Initially, the data suggest a significant increase in the incidence of IE after implantation of the NICE guideline, rising above the projected historical trend. This observation could lead to the hypothesis that the increased incidence of IE could be related to medical procedures in susceptible individuals performed without appropriate antibiotic cover. With regard to the dental procedures, we should observe an increase in the incidence of IE caused by oral viridans group streptococci but, at the present time, no data are available on pathogen-specific causal microorganisms [30].
