[Defining an ethics for preventive trials].
Preventive trials (to prevent from infection) or prophylaxis trials (to avoid consequences of the disease) differ from other clinical trials as they apply to healthy subjects or subjects considering themselves as such: the latter do not ask for intervention even less for trial. Moreover, it is generally an experiment which aims at validating a public health intervention, the individual character of which could appear as secondary regarding the collective interest. It concerns many tools or methods: preventive or prophylactic vaccines and drugs, condoms, impregnated bed nets, etc. The field of implementation of preventive trials is large and covers routine immunization (EPI), large-scale control or eradication of endemic diseases or epidemics, for which the concept of individual risk is generally better understood. Preventive trials imply ethical obligations (high individual or collective benefits and absence of risks as there is no immediate therapeutic compensation), methodological adaptations (because the number of subjects is considerably larger than for therapeutic trials) and a sensitive valorization towards a large population who is not asking for the recommended intervention. As regard the benefits, it is also necessary to consider the costs in comparison with the expected efficacy The methodological constraints are important because the demonstration of both safety and efficacy requires a very large number of subjects to validate the product. It is often necessary to use indirect or substitutive markers and indicators (title of protective antibodies rather than definite clinical protection) which need a preliminary validation. Before carrying out a preventive or prophylactic trial, it is advisable to specify the objectives in order to assess the real profits and absence of risks during the trial and after the implementation of the tested product. Preventive trials require a phase of technological transfer to guarantee the application of the validated tools for the benefit of the population at stake. In this respect, if trials for prevention are now well codified both on ethical and methodological aspects, trials for prophylaxis (filariasis with ivermectin, schistosomiasis with praziquantel, malaria with intermittent "preventive" treatment or HIV with antiretroviral treatment, for example) still remain a difficult issue at both ethical and methodological levels.
CUR Santé de la mère et de l'enfant en milieu tropical, IRD, CP 9214, La Paz, Bolivie. chippaux@ird.fr
J-P
JP
Chippaux
D002986:Clinical Trials as Topic / Q000941:ethics* / Q000379:methods / Q000592:standards; D006805:Human Experimentation / Q000941:ethics* / Q000592:standards; D006801:Humans; D007049:Iatrogenic Disease / Q000517:prevention & control; D011315:Preventive Medicine / Q000941:ethics* / Q000379:methods / Q000592:standards; D035842:Research Subjects; D018570:Risk Assessment