Chief Executive Manon Cox estimated the cost of developing and securing approval for a vaccine could be as high as $1 billion. Without government funding, “that product has got to have a market of a few billion dollars,” she said.

With the help of $43 million in initial funding from the U.S. government, France’s Sanofi is developing a candidate using live attenuated virus. The company is not as far along as some other efforts, but it aims to start human trials next year and is confident it can catch up.

“We’ve got technologies, infrastructure, experience dealing with regulators in this field. All of that gives us a jumpstart,” said Nick Jackson, head of research for Sanofi’s vaccine unit.

Another French vaccine maker, Valneva SE, generated an inactivated Zika vaccine candidate using the same process as its already approved Japanese encephalitis vaccine.

GSK is working with NIAID on a new type of vaccine technology. Japan’s Takeda also secured U.S. government funding to help develop a vaccine using killed Zika virus and plans to begin human testing in the second half of 2017.

“If there is a huge need,” said Dr. Rajeev Venkayya, president of Takeda’s global vaccine unit, “there will be a business model that works.”