Our results indicate that exposure to an audiovisual message about tetanus booster vaccination in a waiting room was associated with an increase in the number of prescriptions presented for tetanus vaccinations. We believe that the audiovisual message broadcast in the waiting rooms attracted the patients' attention and encouraged them to take the active step of asking for the vaccination
Our results contradict those of a study conducted in a similar setting in Canada in 1995 , which focused on posters in waiting rooms encouraging patients to request tetanus vaccinations. The authors did not find that the posters had a significant impact.
The use of audiovisual devices in waiting rooms has been the subject of several studies, in which positive effects were found in non-general practice waiting rooms [15–17]. Furthermore, the effects in general practices of audiovisual devices broadcasting information on subjects other than vaccination have also been studied [18, 19]. Some authors concluded that audiovisual messages had a positive impact, in particular when reinforced by an additional intervention [17, 20, 21]. Our study showed that exposure to a stand-alone audiovisual message about tetanus booster vaccination can be associated with an increase of number of prescriptions for tetanus vaccination.
Clearly the present study suffers from a number of shortcomings. Although no detailed socio-demographic and clinical characteristics of the patient population were available, the six GPs were unaware of major reasons for the two groups to differ. An accurate list of patients cared for by a medical practice and the socio-demographic characteristics of the served population are not readily known because of the following reasons. Healthcare delivery in Belgium is mainly based on the principles of independent medical practice, i.e. independent medical practitioners are paid via fee-for-service payment and there is free choice of doctor by the patient. Patients may register with a doctor of their choice, but registration is not compulsory. Therefore, this situation forced us to use as numerator the number of annual contacts, children and adults included. The fact that the participating GPs were not blinded may be an additional source of bias but almost impossible to avoid in the present circumstances. The investigators relied on their professional and personal behaviour.
It is unclear that the audiovisual message led to a change of patients' behaviour regarding tetanus booster vaccination request. We used an indirect means of measuring change, because we recorded the number of GPs' prescriptions presented to pharmacies by patients in both groups, rather than the number of patient requests. These prescriptions may be subject to various influences, such as the GPs' motivation. Furthermore, providing patients with booster vaccines in a pharmacy does not necessarily mean that the vaccine was injected; the patient may forget to bring the prescribed vaccine dose to their next GP's visit, and it may never be injected.
We also found that, although the audiovisual message was associated with an increased number of tetanus booster vaccine prescriptions, the results could be quite different for other educational messages, such as those regarding more expensive or complex vaccines (e.g., HPV vaccine), or those counselling changes in behaviour (e.g., diet and exercise modifications).
Another factor that should be further examined is the benefit of investing in audiovisual devices. In the field of vaccines, proper use of a simple computerized schedule could perhaps achieve similar results, but requires that GPs use it regularly and that patients regularly visit the same doctor. Audiovisual devices must be shown to be cost effective and efficient for purposes other than vaccination.
Several ethical issues should be addressed in the perspective of a widespread use of such audio-visual devices in waiting rooms. Some issues concern the implications of the GPs themselves in terms of conflict between choosing the types of health messages to promote and the potential income they might generate. There is indeed a risk that the choice of audio-visual messages may be guided not by the potential benefits of such messages on the patients' health but by the increase in paid medical procedures that the audio-visual messages may induce. The involvement of the pharmaceutical industry may also be a problem, in the sense that the choice of audio-visual messages may be partly dictated by pharmaceutical sponsorship. Thus, accounting for ethical issues in audio-visual messages will help identifying the foremost priorities in patient's healthcare needs but also assessing the scientific validation of audio-visual messages in terms of their ability to induce health improvements.
Finally, our study did not address a qualitative concept that should be explored: the patients' opinions and experiences. Did the patients enjoy the messages or did they find them annoying? Were they seeking information, or did they feel saturated with information? How well was the health education message received and understood?