Rotavirus is the single most important enteric pathogen associated with high mortality in infants and young children in developing countries, and is associated with more than an estimated 600 000 deaths annually [4, 5]. Thus, new estimates indicate that rotavirus is responsible for ~5% of total childhood mortality [5, 6]. The reported incidence rates of rotavirus infection do not vary significantly between industrialized countries and the developing countries of Africa and Asia, indicating that socio-economic improvements in water and sanitation may not reduce rotavirus diarrhea . Nevertheless, the inequity in healthcare means that the vast majority of both diarrheal and rotavirus deaths are in children in the poorest countries of the world [1, 8]. In these poor countries, about 1 child in 200 will die of rotavirus disease . This has prompted the international prioritization of rotavirus vaccines as a primary strategy for the reduction of the mortality associated with this infection.
General improvements in the overall severity, management and outcome of diarrheal diseases, due to such global interventions as oral rehydra-tion therapy (ORT) and the Integrated Management of Childhood Illnesses (IMCI), have been observed. However, the effect of these improvements on rotavirus infection, per se, has not been significant, indicating that the successful interventions against the bacterial and parasitic microbes causing diarrheal illness, may have a much less dramatic effect on rotavirus infection. In fact, as estimates of the mortality due to diarrheal diseases decline globally, the proportion of hospitalizations due to severe rotavirus infection has increased, and this is taken as a likely marker for the severity of the diarrheal episode and the potential risk of death due to the infection or complications of the infection.
The latest reviews of rotavirus infection from various regions, including Africa, Asia and Latin America as well as Europe indicate that rotavirus is associated with 25-60% of all hospital admissions for diarrheal diseases [9-13]. Rotavirus-associated illness has been estimated to result in approximately 25 million clinic or emergency room visits and about 2 million hospi-talizations in children less than 5 years of age annually . This tremendous burden of disease and associated mortality is concentrated in the developing countries of Africa and Asia, where over 82% of the rotavirus-associ-ated mortality occurs . Thus, for rotavirus vaccines to truly impact on childhood mortality, the vaccines need to be introduced into these regions and countries.
The current status of rotavirus vaccine development globally has never been more promising. In early 2006, two live oral attenuated rotavirus vac cines completed large-scale safety and efficacy evaluation in Latin America, Europe and the USA [14, 15]. These vaccines have been licensed by the multinational pharmaceutical industry in the USA (RotaTeq®, Merck & Co., Inc., Pennsylvania) and in Europe (Rotarix®, GSK Biologicals, Belgium), which are important as these represent the countries of manufacture, and in many other individual countries. In addition, these licensed vaccines are already being utilized in routine childhood immunization in some countries in the Americas. Finally, several other candidate rotavirus vaccines are under clinical development in partnership with various emerging vaccine producers in developing countries.
The impact of introducing these two rotavirus vaccines in Europe and the USA and in countries in Latin America should contribute significantly to help reduce both the high numbers of hospitalizations and the costs associated with this, as well as reduce the limited rotavirus-associated deaths in these regions [16, 17]. Nevertheless, the true effectiveness of rotavirus vaccines to impact on diarrheal disease mortality in infants and young children in developing countries still needs to be ascertained.
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