(Bloomberg) -- France is starting to vaccinate millions of ducks to rein in bird flu outbreaks in one of the world’s top poultry exporters, even as the move spooks some of its major customers.

The spread of the virus — which can be deadly to domestic birds — has worsened in recent years, with more than 200 million poultry losses globally since late 2021. France’s duck industry, famed for the foie gras delicacy made from their livers, has been among those hit hard, sparking a hunt for new ways to tackle the disease.

That includes vaccines, which have been trialled in several European Union nations, and France is now the first in the bloc to put them into widespread commercial use. The campaign began Sunday and will cost around 100 million euros ($105 million), 85% of which will be subsidized by the government.

About 64 million French ducklings, raised for meat as well as those used for foie gras, are set to receive two shots over a period of a few weeks, with herd immunity expected by the end of the year.

“We’re rather in a phase of relief,” Agriculture Minister Marc Fesneau said during a visit Monday to a farm in the Landes area, a key duck-producing region.

But France’s decision has fueled concerns that vaccinating poultry could mask the circulation of bird flu and risk importers buying infected animals or contaminated products. The pushback from some of the country’s major trade partners could also influence how willing other poultry producers are to use vaccinations.

The US restricted French poultry imports from this month, citing “uncertainty” around the vaccination plans. Canada issued a temporary suspension, and Japan also halted French imports as of Oct. 1. The Asian country was the third-largest market by value for French duck offal and livers as of 2021, as well as a major duck-meat buyer, United Nations data show.

Fesneau said the government is in discussions with countries, including Japan, that are wary about importing vaccinated ducks.

“We have an extremely strict health monitoring process in place, and that’s what also helps bring credibility to the vaccination campaign,” he said.

--With assistance from Shoko Oda.

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