Satellite Symposium on Challenges to Enteric Vaccines: Salvador de Bahia, Brazil, 12 June 2005

Abstract

Salvador de Bahia, Brazil, 12 June 2005Background and rationaleIn an effort to promote vaccine research and development of enteric vaccines, including cholera, typhoid fever, and rotavirus vaccines and to address the challenges for their future implementation, the WHO Initiative for Vaccine Research hosted a one-day Satellite Symposium dedicated to addressing the opportunities to use the licensed vaccines against cholera and typhoid fever and to consider the challenges which remain for introduction of rotavirus vaccine, including clinical trials in developing-country settings. The Bill and Melinda Gates Foundation graciously provided US$ 50,000 to organize the Satellite Symposium.The Symposium was followed by a three-day Global Vaccine Research Forum, which also included a session on the other two important enteric vaccines against enterotoxigenic Escherichia coli and Shigella. The Forum brought together a world-wide selection of top researchers and scientists and served as a forum for the partners of GAVI (the Global Alliance for Vaccines and Immunization) to discuss vaccine research and development issues and to update research agenda. Moreover, both the meetings provided an opportunity for discussion of broader issues of vaccine policy and implementation.Goals, objectives, and activitiesAlthough diarrhoeal mortality, globally, is observed to be on the decrease, it is well-recognized that the vast bulk of morbidity and mortality of the estimated annual 1.9 million deaths is borne by infants and young children living in developing countries. The Symposium addressed the challenges and opportunities for the effective implementation of these vaccines in the regions where they are most needed.Currently, two vaccines are licensed for cholera, but are not yet readily used in the areas considered endemic for cholera, nor in children who are largely affected by the disease. Two recent studies have demonstrated that (a) cholera vaccine can be administered in mass immunization campaigns in areas where cholera is endemic with good protective effects and (b) that there appears to be good herd protection in vaccinated populations and non-vaccinated individuals. The remaining challenges include identifying and overcoming the obstacles to implementation of the vaccines in these settings. Similarly, the typhoid fever vaccines are licensed and have been proven to be effective in preventing the disease and can be administered in school-age populations with good protection given.The present state of development of rotavirus vaccines indicates an urgent need to increase the global capacity to conduct multiple clinical trials in developing countries, particularly in Africa and Asia. These trials will need to evaluate safety, immunogenicity, and efficacy of the vaccine candidates in different populations and geographical areas which differ significantly in epidemiology of the virus and viral strain diversity and in the social, health, and economical background of the population-all of which may have a significant impact on final efficacy results.The agenda of the Symposium (attached) included different sessions focused on different enteric vaccines, which allowed for discussion of priority issues which have been identified as major obstacles for the implementation of vaccines against cholera and typhoid fever and the introduction of rotavirus vaccines.The participants of the Satellite Symposium were provided with an opportunity to attend all other sessions of the Forum to interact and share their experiences with experts working on other infectious diseases or areas. The linking of the Symposium with the Global Vaccine Research Forum has, thus, provided an ideal forum for cross-field interactions, exchange of information, and sharing of experiences between scientists against other priority infectious diseases, such as HIV, tuberculosis, malaria, and other infections, including enterotoxigenic E. …