predominantly in the cold months of the year (Kapikian et al., 1982; Rodriguez et al., 1980). In contrast, in the tropical developing countries, rotavirus infection occurs year-round (Soenarto et al., 1981).
The disease burden estimates for rotavirus, assuming current levels of intervention, are shown in Table D-13.1, and their derivations are discussed in Appendix C. The estimates based on a scenario in which oral rehydration therapy prevents 50 percent of rotavirus deaths are shown in Table D-13.2.
The principal target for a rotavirus vaccine is the young infant in the first few months of life. Vaccination at this stage should reduce the morbidity and mortality associated with clinical rotavirus infection in the early years. A secondary target might be women of childbearing age. This approach could increase the titer of rotavirus antibody in breast milk to protect nursing infants. The advantage of such passive protection is reduced by the already generally mild or asymptomatic nature of neonatal rotavirus infection and by the small protection afforded by maternal antibody against future symptomatic disease.
Rotavirus vaccine appears to be an ideal candidate for inclusion in the World Health Organization Expanded Program on Immunization (WHO-EPI). The target for rotavirus vaccine is precisely the age group currently covered by the EPI program. The immunogenicity of a rotavirus vaccine in this age group remains to be demonstrated, but no special problems are anticipated (in contrast to bacterial polysaccharide vaccines, which may elicit a poor antibody response). In addition, the compatibility of the live virus vaccine with other vaccines given by the oral route must be determined. These are vaccine development problems, and there are no theoretical reasons why they cannot be solved.
Assuming administration of a hypothetically perfect vaccine (conferring long-lasting immunity with one dose) in the first few months of life, the overwhelming majority of the disease burden
Vaccine preventable illness is defined as that portion of the disease burden that could be prevented by immunization of the entire target population (at the anticipated age of administration) with a hypothetical vaccine that is 100 percent effective (see Chapter 7).