Sanofi faces a formal antitrust investigation by the European Commission over allegations that it launched a misleading campaign against rival flu vaccine Fluad made by CSL Seqirus. The probe centers on communications directed at healthcare professionals in Germany and France that European regulators claim disparaged the competing vaccine and contradicted national vaccination recommendations.

Regulators are examining claims that Sanofi questioned the scientific evidence supporting Fluad and suggested unresolved objections from medical societies in Germany. Competition chief Teresa Ribera emphasized that unbiased scientific evaluations are essential for public health policies, framing the investigation as addressing practices that damage competition and consumer choice. The probe follows antitrust raids conducted in September of the previous year.

This investigation arrives as Sanofi navigates challenges under new CEO Belén Garijo, who recently replaced Paul Hudson after disappointing clinical trial results in multiple sclerosis and eczema treatments. The company relies heavily on Dupixent, which generated over a third of its 2025 revenues, though the blockbuster asthma drug faces patent expiration in the early 2030s.

Sanofi shares showed no movement in midday Paris trading as the company maintained it acted in full compliance with competition law and is cooperating with investigators. The probe carries potential penalties of up to 10 percent of worldwide annual turnover under EU antitrust rules.