(CNN) – If an avian influenza pandemic ever hit the United States, there’s only one dependable manufacturer in the country capable of making a vaccine, a government watchdog reports.

“The U.S. government may not be able to rely on foreign countries to allow exports of pandemic vaccine because each country will likely prioritize those vaccines for its own population,” the nonpartisan Government Accountability Office said in a new report.

These forms of the virus mainly infect birds, but certain strains have mutated to transmit from birds to humans, meaning an outbreak among humans is possible — and the U.S. may not be ready.

About 90-95 percent of the national stockpile of pandemic influenza…