Rotavirus vaccines against diarrhoeal disease

Abstract

Rotaviruses are responsible for more diarrhoeal disease-associated mortality than any other single agent. Vaccination may therefore hold the key to combating diarrhoeal disease worldwide. Natural immunity to rotavirus infection indicates that rather than protection from reinfection such immunity gives rise to less severe and less frequent attacks of diarrhoea. Early attempts to design a rotavirus vaccine with bovine rotavirus failed because of poor efficacy in some developing countries. Research into rhesus rotavirus, particularly the high-titre rhesus rotavirus tetravalent (RRV-TV) vaccine, has given slightly better results. A stumbling block to truly effective oral vaccines seems to be immunogenicity in developing countries. If efficacy can be ensured by trials in the developing countries, money spent on rotavirus vaccines will be well spent.

PIP: Rotavirus infection is responsible for more diarrheal disease-associated mortality (about 600,000 deaths per year) than any other single agent. The finding, in developed countries, that clinically significant rotavirus gastroenteritis seldom occurs twice in the same child suggests a build-up of natural immunity against rotavirus in the first year of life. In developing countries, such immunity gives rise to less severe and less frequent attacks of diarrhea. Rhesus rotavirus vaccine was shown to be a more immunogenic candidate than the earlier bovine rotavirus vaccines and rhesus-human reassortant rotaviruses have been developed. Although the high-titer rhesus rotavirus tetravalent vaccine has been effective in developed countries, efficacy in developing countries has been disappointing (50-60% in Brazil and Peru). However, in many Asian and African countries, even an efficacy of 50-60% could prevent a substantial number of deaths. If decision makers in developing countries are to be convinced to introduce rotavirus vaccine into national immunization programs, large-scale demonstration projects that show effectiveness (rather than efficacy) and cost-benefit are essential. The theoretical possibility of interference of rotavirus vaccine with oral poliomyelitis vaccine must also be addressed.