Sanofi spends $2.2B to acquire Dynavax, giving vaccine series a shot in the arm
Sanofi is expanding its vaccine portfolio and product line by acquiring Dynavax Technologies, a $2.2 billion deal that brings assets that could give the company a competitive advantage over products sold by rival vaccine maker GSK.
The terms of the acquisition announced Wednesday call for Sanofi to pay $15.50 in cash for each share of Dynavax, a 39% premium to the stock's closing price on Tuesday. Emeryville, Calif.-based Dynavax went public in 2004 and priced its stock at $7.50 a share.
Heplisav B is a hepatitis B vaccine approved for adults in the United States and Europe and is Dynavax's only commercial product. The vaccine is given as two intramuscular injections, one month apart. By comparison, GlaxoSmithKline's Engerix-B (a hepatitis B vaccine) and Twinrix (which prevents hepatitis A and B) both use a three-shot six-month regimen. Dynavax claims its vaccine gives patients high levels of protective antibodies more quickly than other vaccines and has a similar safety profile.
Dynavax reports 2024 Heplisav B sales of $268.4 million, a 26% increase from the previous year. The company said in its third-quarter 2025 financial results report that it expects the product to increase its share of the hepatitis B vaccine market to 46% from 44% in 2024.
Sanofi's hepatitis B vaccine only covers children. Vaxelis, commercialized in partnership with Merck, protects against hepatitis B and five other pathogens. Vaxelis, approved by the FDA in 2023, is given as three injections over six months, covering use in children 6 weeks to 4 years old.
Dynavax's pipeline includes herpes zoster vaccine candidate Z-1018. In August, the company reported encouraging preliminary data from an early-stage study that tested the vaccine head-to-head against Shingrix, the GlaxoSmithKline product that currently dominates the shingles vaccine market. Dynavax said its shingles vaccine was well tolerated, with fewer reactions after local and systemic injection compared with Shingrix. Robust immune responses were reported across all doses, including the dose selected to enter the second part of the Phase 1/2 study; preliminary data are expected in the second half of 2026.
“Dynavax strengthens Sanofi's adult immunization capabilities by adding differentiated vaccines that complement Sanofi's expertise,” Thomas Triomphe, executive vice president of Sanofi's vaccines business, said in a prepared statement. “Their marketed adult hepatitis B vaccine and shingles vaccine candidates bring new options to our portfolio and underscore our commitment to delivering vaccine protection across the lifespan.”
The acquisition announcement comes as the hepatitis B vaccine faces increased regulatory scrutiny from the Trump administration. In early December, the Advisory Committee on Immunization Practices (ACIP), which makes vaccine recommendations to the Centers for Disease Control and Prevention, voted to recommend shared decision-making for hepatitis B vaccination of children. This recommendation is weaker than ACIP's decades-long recommendation to start vaccinations at birth.
William Blair analyst Matt Phipps believes the acquisition makes sense for Dynavax given growing regulatory concerns surrounding vaccines and investor questions about management's value creation strategy. It also makes sense for Sanofi.
“Sanofi is a logical acquisition partner for Dynavax because of the company's broad vaccine capabilities, but the company does not have adult hepatitis B or shingles programs in its portfolio,” Phipps said in a research note.
In addition to its shingles vaccine candidate, Dynavax's pipeline includes a plague vaccine developed in partnership with the U.S. Department of Defense, as well as fully-owned clinical-stage programs for pandemic influenza and Lyme disease. In November, Dynavax acquired global rights to Vaxart's oral Covid-19 vaccine candidate, which is currently in mid-stage testing. Under the terms of the deal, Dynavax paid $25 million upfront and made a $5 million equity investment in Vaxart.
Dynavax is Sanofi’s second vaccine M&A deal this year. In July, the pharmaceutical giant agreed to pay $1.15 billion to acquire Vicebio, a startup leading programs in early-stage development of bivalent vaccines against respiratory syncytial virus (RSV) and human metapneumovirus (hMPV).
Sanofi said it will use available cash resources to fund the acquisition of Dynavax. Dynavax's board of directors has approved the deal, but it still requires a majority of shareholders to tender their shares. The transaction is expected to close in the first quarter of 2026.
Photo: Francesco Carta fotografo, Getty Images
