ABSTRACT
INTRODUCTION Most conventional vaccines generally require multiple recall injections to achieve sustained and optimal antibody responses. In many developing countries, however, the dropout rates for multiple administration immunization programs is high and can reach 70% (Aguado, 1993). One strategy to overcome this problem would be to convert conventional multiple-dose vaccines to single-dose vaccines with the same or increased effectiveness. Application of such single-shot vaccination would reach a greater percentage of the target population and produce protective antibody levels.
