|Fact sheet No 117: Dengue and Dengue Haemorrhagic Fever - Revised November 1998 (WHO, 1998, 3 p.)|
|Prevention and Control|
Vaccine development for dengue and DHF is difficult because any of four different viruses may cause disease, and because protection against only one or two dengue viruses could actually increase the risk of more serious disease. Nonetheless, progress is gradually being made in the development of vaccines that may protect against all four dengue viruses. Such products could be commercially available within several years.