Why is the Correze (France) running out of flu vaccines?

In France, the Correze area is running out of flu vaccines, seemingly because the flu shot as been very popular this season. Pharmacies are having to help each other with stocks as vaccine makers aren't providing more. Twice as many people as last year have had their flu jab in pharmacies this season. Vaccine makers are offering to collect spare vaccines in other regions to deliver them to the regions where pharmacy based flu vaccinations are being trialled