Sanofi to acquire Dynavax for approximately $2.2 billion, expanding its vaccine portfolio

French pharmaceutical company Sanofi has announced that it will acquire the American biotech firm Dynavax Technologies for approximately $2.2 billion (€1.9 billion). The deal will add an adult hepatitis B vaccine and a promising experimental shingles vaccine to Sanofi’s portfolio, CNBC reports.

According to analysts, the acquisition will help Sanofi diversify its vaccine business at a time when U.S. pediatric immunization policy is shifting. The Donald Trump administration has already moved away from the long-standing universal recommendation for hepatitis B vaccination in newborns—a decision that has sparked sharp reactions within the medical community. Other changes for 2026 are also under discussion.

News of the deal led to a nearly 39% surge in Dynavax shares, which reached $15.45 during U.S. trading. Sanofi shares fell by 0.7%.

“We believe the acquisition is logical against the backdrop of increasing regulatory risks surrounding vaccines,” commented William Blair analyst Matt Phipps. According to him, Sanofi is a natural buyer for Dynavax, as it possesses strong vaccine capabilities but has lacked products for adult hepatitis B or shingles until now.

Sanofi is actively seeking new revenue sources ahead of the 2031 patent expiration of its leading asthma drug, Dupixent. In July, the company acquired British vaccine developer Vicebio for $1.5 billion, following the finalization of a deal worth up to $9.5 billion for Blueprint Medicines.

Under the terms of the current deal, Sanofi will pay $15.50 per Dynavax share, representing a 39% premium over Tuesday’s closing price of $11.13. The company will fund the acquisition with cash on hand and expects it to be completed in the first quarter of 2026, with no impact on 2025 financial results.

Earlier this year, Sanofi and its British rival GSK reported pressure in the U.S. influenza vaccine market, while Australia’s CSL postponed plans to spin off its vaccine division due to lower-than-expected immunization rates in the U.S.

Dynavax’s primary product, Heplisav-B, is a hepatitis B vaccine for individuals over 18. It is administered in two doses over one month, unlike other vaccines that require three doses over six months. In the third quarter of 2025, the vaccine generated $90 million in revenue, with analysts expecting peak annual U.S. sales of approximately $609 million.

The deal also includes the experimental shingles vaccine Z-1018, which could generate revenue after 2030 if safety and efficacy results are confirmed in larger clinical trials. The shingles vaccine market is currently dominated by GSK’s Shingrix, which is expected to bring in approximately €4 billion in revenue this year. In a study of 92 people aged 50–69, Z-1018 showed a similar immune response but a better safety profile.

Separately, Sanofi reported that the U.S. Food and Drug Administration (FDA) has refused to approve its experimental drug tolebrutinib for slowing disability progression in a form of multiple sclerosis. Sanofi’s Head of Research and Development, Houman Ashrafian, stated that the decision was unexpected and represented a sharp departure from previous feedback from the regulator.

The rejection adds to a series of disappointing news regarding Sanofi’s experimental products this year, which has negatively impacted the company’s stock performance relative to the broader European pharmaceutical sector.