Sanofi is boosting its vaccine portfolio and pipeline through the acquisition of Dynavax Technologies, a $2.2 billion deal bringing assets that could give the company competitive advantages over products marketed by rival vaccines maker GSK.
The acquisition terms announced Wednesday call for Sanofi to pay $15.50 in cash for each share of Dynavax, representing a 39% premium to the stock’s Tuesday closing price. When Emeryville, California-based Dynavax went public in 2004, it priced its shares at $7.50 apiece.
Heplisav B, a hepatitis B vaccine approved in the U.S. and Europe for adults, is Dynavax’s sole commercialized product. This vaccine is administered as two intramuscular injections one month apart. By contrast, GSK’s Engerix-B, a hepatitis B vaccine, and Twinrix, which protects against both hepatitis A and B, are both administered in a three-shot regimen across six months. Dynavax contends its vaccine enables a patient to achieve high levels of protective antibodies faster than other vaccines and with a similar safety profile.
Dynavax reported $268.4 million in Heplisav B sales in 2024, a 26% increase compared to the prior year. In its report of third quarter 2025 financial results, the company said it estimates this product increased its share of the hepatitis B vaccines market to 46%, up from 44% in 2024.
Sanofi’s presence in hepatitis B vaccines covers only children. Vaxelis, commercialized under a partnership with Merck, protects against hepatitis B and five other pathogens. The 2023 FDA approval of Vaxelis, given in a three-shot series over six months, covers its use in children from age 6 weeks through 4 years old.
The Dynavax pipeline includes the shingles vaccine candidate Z-1018. In August, the company reported encouraging preliminary data from an early-stage study that tested this vaccine head to head against Shingrix, the GSK product that currently dominates the shingles vaccine market. Dynavax said its shingles vaccine was well tolerated, showing lower local and systemic post-injection reactions compared to Shingrix. Robust immune responses were reported at all doses, including the dose selected to advance to the second part of the Phase 1/2 study; preliminary data are expected in the second half of 2026.
“Dynavax enhances Sanofi’s adult immunization presence by adding differentiated vaccines that complement Sanofi’s expertise,” Thomas Triomphe, Sanofi’s executive vice president, vaccines, said in a prepared statement. “Its marketed adult hepatitis B vaccine and shingles candidate bring new options to our portfolio and underscore our commitment to providing vaccine protection across the lifespan.”
The acquisition announcement comes as hepatitis B vaccines face greater regulatory scrutiny from the Trump administration. In early December, the Advisory Committee on Immunization Practices (ACIP), a panel that makes vaccine recommendations to the Centers for Disease Control and Prevention, voted to recommend shared decision making for hepatitis B vaccination for children. That’s a weaker recommendation than the ACIP’s decades-old recommendation that these vaccinations start at birth.
To William Blair analyst Matt Phipps, the acquisition makes sense for Dynavax given growing regulatory concerns around vaccines and investor questions on management’s strategy for value creation. It also makes sense for Sanofi.
“Sanofi is a logical acquisition partner for Dynavax given the company has extensive vaccine capabilities but the portfolio does not have an adult hepatitis B or shingles program,” Phipps said in a research note.
Besides the shingles vaccine candidate, the Dynavax pipeline includes a plague vaccine in development under a partnership with the U.S. Department of Defense as well as wholly owned clinical-stage programs for pandemic influenza and Lyme disease. In November, Dynavax licensed global rights to Vaxart’s oral Covid-19 vaccine candidate, currently in mid-stage testing. Per deal terms, Dynavax paid $25 million up front and made a $5 million equity investment in Vaxart.
Dynavax is Sanofi’s second vaccines M&A deal this year. In July, the pharmaceutical giant agreed to pay $1.15 billion to buy Vicebio, a startup whose lead program is a bivalent vaccine in early-stage development for respiratory syncytial virus (RSV) and human metapneumovirus (hMPV).
Sanofi said it will finance the Dynavax acquisition with available cash resources. The Dynavax board of directors has approved the deal, which 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
