A French pharmaceutical company developing a Zika vaccine funded with millions of dollars in research grants from the U.S. government has rejected a request from the U.S. Army to set an affordable price for the drug once it becomes available.

Sanofi Pasteur has already received $43 million from the Department of Health and Human Services, and the U.S. Army intends to award an exclusive contract to the company to license and sell a vaccine based on technology discovered using federal money.

Scientists with the Walter Reed Army Institute of Research, which is part of the Defense Department, began early-stage clinical trials in November -with Sanofi as a research partner.

But the Army's intention to award an exclusive deal for Sanofi has angered some lawmakers who argue that the drugmaker would be able to charge whatever price it wants for the vaccine.

This is not the only clinical trial of a Zika vaccine taking place. As the first place in the continental United States with a confirmed outbreak of Zika spread by mosquitoes last summer, Miami is one of three sites where plan a second phase of a clinical trial testing a different experimental DNA vaccine.

The was developed by federal government scientists with the National Institute of Allergy and Infectious Diseases, which is part of the National Institutes of Health.