PARIS/LONDON (Reuters) - Sanofi has launched a project to develop a vaccine against the Zika virus in the most decisive commitment yet by a major vaccine producer to fight the disease linked to multiple birth defects in Brazil.

The French drugmaker said on Tuesday its Sanofi Pasteur vaccines division would use its expertise in developing vaccines for similar viruses such as yellow fever, Japanese encephalitis and, most recently, dengue.

The move comes a day after the World Health Organization declared the mosquito-borne Zika virus to be an international public health emergency due to its link to underdeveloped brains in some babies.

Such emergency declarations are a way for the WHO to mobilise resources and coordinate action to fight a disease, and Director-General Margaret Chan said on Monday that one of the priorities was to develop a vaccine as fast as possible.

“Sanofi Pasteur is responding to the global call to action to develop a Zika vaccine given the disease’s rapid spread and possible medical complications,” said Nicholas Jackson, research head of Sanofi Pasteur, who is leading the new Zika vaccine project.

Sanofi believes its established research and industrial infrastructure for its newly licensed dengue vaccine can be rapidly leveraged to help speed identification of a Zika vaccine candidate.

So far, the only groups with firm plans to develop a Zika vaccine are small biotech companies and academic institutions, although GlaxoSmithKline has said it is concluding feasibility studies to evaluate if its vaccine technology is suitable.

Currently, there is no vaccine or treatment for Zika, since the disease, until recently, has not been seen a serious public health concern.

Zika typically causes mild fevers and rashes and about 80 percent of those infected show no symptoms. But its link to microcephaly, or small heads, and other neurological disorders in newborns has catapulted it up the global health agenda.

The WHO last declared such a public health emergency for Ebola.

Zika is closely related to dengue and is spread by the same species of mosquito. It also has similar symptoms, including fever, rash, joint swelling and headaches. Nonetheless, developing a vaccine for Zika is a major undertaking, involving much research and clinical trials.

The closest vaccine prospect so far may be from a consortium including U.S. biotech company Inovio Pharmaceuticals, which could potentially have a vaccine ready for limited emergency use before year-end, according to one of its lead developers.