Sanofi has filed two separate federal lawsuits against Moderna and Pfizer, alleging that several major Covid-19 and RSV vaccines infringe its mRNA delivery patents.
The French pharmaceutical giant, listed on US markets as (SNY), is pursuing royalties through its Translate Bio unit, which it acquired for $3.2 billion in 2021.
One complaint targets Moderna’s Spikevax and mNexspike Covid-19 vaccines alongside its mResvia RSV shot, alleging infringement of 10 patents covering mRNA delivery methods and compositions.
A separate complaint alleges that Pfizer’s Comirnaty Covid-19 vaccine infringes eight of those same patents related to Translate Bio’s technology portfolio.
Both lawsuits were filed in the US District Court for the District of New Jersey, placing the cases in a jurisdiction that handles significant pharmaceutical patent litigation.
Central to Sanofi’s claims are lipid nanoparticles, the tiny protective shells that carry mRNA into human cells, which the company says were developed and patented by Translate Bio.
Sanofi stated it was “seeking fair compensation for use of its patented technology” and made clear it is not seeking to halt sales of any of the vaccines named in its complaints.
The company’s US-listed shares rose approximately 1.1% following news of the filings, while Moderna advanced roughly 1.2% and Pfizer’s vaccine partner BioNTech SE gained about 1.7%.
The litigation adds to an already crowded field of patent disputes surrounding Comirnaty, with Pfizer’s March quarterly filing listing five other claimant groups in patent actions before Sanofi even filed its complaint, spanning both the United States and Europe.
One financial reference point for potential damages is Moderna’s March settlement of a separate lipid-nanoparticle dispute, in which the company agreed to pay $950 million upfront and as much as an additional $1.3 billion, for a maximum total of $2.25 billion.
Pfizer’s Comirnaty generated $232 million during the first quarter of 2026, a decline of 59%, reflecting lower contractual deliveries overseas and a narrower US vaccination recommendation.
The cases therefore concern a substantial base of past vaccine sales tied to products that now represent a relatively minor portion of quarterly revenue for both Pfizer and Moderna.
Sanofi’s move signals a broader push by established pharmaceutical companies to extract value from mRNA intellectual property developed during the Covid-19 pandemic era.
The outcomes of these suits could set significant precedents for how mRNA vaccine technology royalties are valued and enforced across the global pharmaceutical industry going forward.