Evaluation of vaccines against enteric infections: a clinical and public health research agenda for developing countries.

Enteric infections are a major cause of morbidity and mortality in developing countries. To date, vaccines have played a limited role in public health efforts to control enteric infections. Licensed vaccines exist for cholera and typhoid, but these vaccines are used primarily for travellers; and there are two internationally licensed vaccines for rotavirus, but they are mainly used in affluent countries. The reasons that enteric vaccines are little used in developing countries are multiple, and certainly include financial and political constraints. Also important is the need for more cogent evidence on the performance of enteric vaccines in developing country populations. A partial inventory of research questions would include: (i) does the vaccine perform well in the most relevant settings? (ii) does the vaccine perform well in all epidemiologically relevant age groups? (iii) is there adequate evidence of vaccine safety once the vaccines have been deployed in developing countries? (iv) how effective is the vaccine when given in conjunction with non-vaccine cointerventions? (v) what is the level of vaccine protection against all relevant outcomes? and (vi) what is the expected population level of vaccine protection, including both direct and herd vaccine protective effects? Provision of evidence addressing these questions will help expand the use of enteric vaccines in developing countries.