Clinical and immunological studies of rotavirus vaccines.

The RIT 4237 bovine rotavirus vaccine has served as a useful model for rotavirus vaccination, but the vaccine will not be further developed or tested. The main problem encountered with this vaccine was its poor "take" rate in developing countries. The reasons for this are unclear, and it is not known whether other bovine rotavirus vaccines are more efficacious in this respect. WC-3 bovine rotavirus vaccine will shortly be tested at several sites in developing countries. The rhesus rotavirus vaccine RRV-1 does not appear by itself to be a practical vaccine either. It has induced only moderate protection against human rotavirus serotypes other than the vaccine type. However, the fact that RRV-1 vaccine has induced substantial protection against severe diarrhoea caused by serotype 3 rotavirus, even in young infants, is promising and supports the concept that serotype-specific neutralizing antibodies play a role in protection against human rotavirus disease. Based on this concept, it has been possible to develop reassortant rhesus rotaviruses in which one RNA segment of human rotavirus, which encodes the expression of VP7 antigen, has been incorporated (Kapikian et al., 1986; 1987). Such rhesus-human reassortant rotaviruses, representing serotypes 1, 2 and 4 of human rotavirus and serotype 3 of rhesus rotavirus, can be combined to make a tetravalent vaccine that might induce neutralizing antibodies against each of the main serotypes of human rotavirus. Although its efficacy is unproven, such a combination vaccine is presently regarded as the most promising candidate rotavirus vaccine for the prevention of human rotavirus disease.