Vaccines against traveler's diarrhoea and rotavirus disease - a review.

Diarrheal diseases constitute one of the most important health problems worldwide, preferentially in developing countries with a morbidity of estimated 5 billion and a mortality of 5 million cases per year. Children less than 5 years are particularly in danger with respect to the incidence and severity of the gastrointestinal symptoms. Travelers to developing countries are also at risk to develop diarrheal disorders; around 30-50% of them acquire so called "travelers's diarrhea" caused by bacteria, viruses or protozoa. It has been estimated that approximately 30-70% of diarrhea are due to bacteria, of which the most frequently detected enteric pathogens are non-invasive, enterotoxigenic Escherichia coli (ETEC). Their exotoxins, the heat stabile (ST) and the heat labile (LT) toxins are in large part responsible for the pathogenicity of the bacteria. About 20% of cases of traveler's diarrhea are caused by LT producing ETEC. This heat labile toxin exhibits a 80% sequence homology with cholera toxin. The presently available vaccine against cholera (Dukoral) contains inactivated Vibrio cholerae bacteria and the recombinant non-toxic B subunit of cholera toxin. Consequently, this vaccine displays also some efficacy against traveler's diarrhoea with up to 25% of travelers being protected against this disease. Rotaviruses are the leading recognized cause of diarrhoea-related illness and deaths among infants worldwide in developing and industrialized countries. Based on the high incidence of this disease two oral vaccines have been developed and will be available in Europe in 2006. Due to the impact of rotavirus diseases also in Austria vaccination against this disease has been already suggested in the Austrian vaccination schedules for infants from 6-24 weeks of age. One of the two vaccines, Rotarix, is an attenuated monovalent vaccine with a broad cross-reactivity against the most frequent serotypes. The second one, RotaTeq, is a pentavalent attenuated vaccine containing 5 human-bovine reassortants. Both vaccines display 85-98% efficacy against severe rotavirus disease and an excellent tolerability with no difference in side reactions to the placebo controls, particularly with respect to intussusceptions. With respect to increasing travel habits with infants and small children, particularly when visiting friends and relatives, vaccination against rotavirus infections will also be important in international travel.