Current status of dengue vaccines and prospects for the future.

Dengue vaccine development is complicated by the existence of four viral serotypes, the lack of in vitro assays of virulence for humans and the lack of an animal model for assessing viral attenuation. Experience gained from human testing shows that the in vitro phenotypic growth characteristics used for selecting candidate dengue viruses do not always correlate with lack of pathogenicity in vivo. While testing continues on live, attenuated, viral strains, alternative dengue vaccine products produced as recombinant subunit vaccines are being sought.