Vaccination coverage is insufficient for influenza, pneumococcus, and herpes zoster in people over the age of 65 in France, even though these are common infectious diseases. Using a computerised questionnaire, the aim of our study was to assess the knowledge of general practitioners, geriatricians, infectious diseases specialists and interns in the Loire region about the vaccination against these three diseases in elderly subjects, to identify the obstacles to vaccination, and to evaluate whether the provision of knowledge modifies the prescriptions and vaccination recommendations made to patients. Of the 125 responses from doctors and interns, 90.2 % are correct for influenza, 69.2 % for pneumococcus, and 32.8 % for herpes zoster, with no significant difference between specialities. By providing information, practitioners are more willing to vaccinate their patients against influenza (99 %), pneumococcus (93 %), and herpes zoster (39 %). The main obstacles to vaccination are the patient's refusal (85 %), the doctor's lack of knowledge and time (70 % and 41 % respectively), doubts about the vaccine's effectiveness (28 %), and fear of side effects (21 %).