Sanofi hopes to launch the world's first dengue fever vaccine in early 2015, putting it around five years ahead of rival shots against the mosquito-borne disease.

Developing a vaccine against dengue is tricky, since there are four closely related viruses that can cause the disease and researchers lack good animal models to test immune responses.

But several research teams and commercial companies are making progress.

The following vaccine candidates are in development, with stage of testing in the three-phase clinical trial process: * Sanofi Pasteur, vaccine unit of Sanofi: Phase III * Inviragen, working with Centers for Disease Control and Prevention: Phase II * GlaxoSmithKline, working with Walter Reed Army Institute of Research: Phase I * Merck, programme acquired from Hawaii Biotech: Phase I * National Institutes of Health, working on a non-exclusive licence basis with India's Biological E and Panacea Biotec, Brazil's Butantan and Vietnam's Vabiotech: Phase I

Source: Dengue Vaccine Initiative www.denguevaccines.org