Authorities in the mountainous Hautes-Alpes region of south-eastern France said the infection, which can spread to humans and is deadly in its rarest forms, has spread to 28 farms since June.
French vets have been battling to contain the outbreak, as the Spanish laboratory that produces the vaccines has been closed throughout August for the summer holiday.
"The state is in talks with its European partners to discuss the availability and purchase of vaccines" which other countries may have stockpiled, regional official Agnes Chavanon said Sunday.
Hautes-Alpes official Serge Cavalli said animals were being vaccinated at the region’s affected farms, which have been banned from production for at least 21 days. This to disinfect the farms and provide time for the vaccinated animals to become immune. Any milk on site is pasteurised and then destroyed.
The first case in the current outbreak was detected in the village of Montgardin on 28 June, killing six cows. It has since spread to 12 other rural towns.
Cows struck by anthrax swell in the abdomen and bleed from their orifices, and often die in less than 24 hours.
Anthrax is transmitted by spores that can stay inactive in the ground for decades, including in the bodies of dead animals.
The last serious French outbreak was in 2008 when anthrax spread to 23 farms, most of them in the eastern Doubs area.
Rare but dangerous for humans
The regional health agency (ARS) said 103 people in the Hautes-Alpes region had been flagged as having potentially come into contact with infected animals, most of them farmers, vets or slaughterhouse workers.
Half have been given preventative antibiotics, according to officials.
Cases of anthrax being passed on to humans are "extremely rare", said Christine Ortmans of the ARS.
Cutaneous anthrax -- which appears on the skin and is by far the most common form of the infection -- is rarely deadly when treated with antibiotics.
No one has been reported ill during the current outbreak, Ortmans stressed.
But the bacteria that causes it, bacillus anthracis, produces a powerful toxin and has been used as a biological weapon. Most notoriously in a series of US attacks in the aftermath of the 11 September attacks in 2001, when anthrax delivered through the mail killed five and left 17 others ill.