Sanofi bets $2.2bn on Dynavax to expand adult vaccine pipeline with hepatitis B and shingles focus

Sanofi (NASDAQ: SNY; EURONEXT: SAN) has entered into a definitive agreement to acquire Dynavax Technologies Corporation (NASDAQ: DVAX) for $2.2 billion in cash, in a move aimed at strengthening its adult immunization portfolio. The deal brings Dynavax’s U.S.-approved hepatitis B vaccine HEPLISAV-B and its phase 1/2 shingles vaccine candidate into Sanofi’s pipeline at a time when global adult vaccination demand is on the rise.

The transaction gives Sanofi immediate access to a differentiated, two-dose hepatitis B vaccine and a platform adjuvant technology via toll-like receptor (TLR) agonists, while also offering long-term optionality in shingles—a disease with both high prevalence and unmet need among older adults. The acquisition is expected to close in the first quarter of 2026, pending regulatory approvals.

Why Dynavax’s HEPLISAV-B fills a strategic hole in Sanofi’s adult immunization portfolio

Dynavax’s HEPLISAV-B continues to stand out in the competitive hepatitis B vaccine market due to its clinically validated, simplified two-dose regimen administered over one month. This design contrasts with conventional hepatitis B vaccines, which typically require a three-dose schedule over six months, often leading to lower completion rates in adult populations. HEPLISAV-B combines the hepatitis B surface antigen with Dynavax’s proprietary CpG 1018 adjuvant, a toll-like receptor 9 (TLR9) agonist that stimulates a more rapid and robust immune response. Clinical studies have consistently demonstrated that HEPLISAV-B achieves higher and faster seroprotection rates compared to legacy regimens—an important advantage in public health contexts where adherence and speed of immunity are critical.

For Sanofi, the acquisition of HEPLISAV-B represents both a strategic entry into adult routine immunization and a structural diversification beyond its current vaccine portfolio, which is heavily weighted toward pediatric and seasonal influenza products. Adult hepatitis B vaccination remains a significantly underpenetrated opportunity in the United States and globally. The U.S. Centers for Disease Control and Prevention (CDC) estimates that approximately 100 million adults born before universal childhood hepatitis B vaccination began in 1991 remain unvaccinated. This population is at ongoing risk for chronic hepatitis B infection, a condition that can lead to cirrhosis, liver failure, and hepatocellular carcinoma, underscoring the long-term clinical and commercial relevance of adult hepatitis B immunization strategies.

Beyond the immediate commercial value, Sanofi’s acquisition of Dynavax signals a broader platform ambition. The CpG 1018 adjuvant exemplifies a new class of synthetic immune stimulators capable of enhancing both humoral and cellular responses. This technology has far-reaching potential across next-generation vaccine modalities, particularly in enhancing the immunogenicity of subunit vaccines, expanding the utility of mRNA constructs, and enabling combination immunizations for adults with comorbidities or immunosenescence. Sanofi has previously emphasized its interest in differentiated adjuvant technologies to compete more effectively against GlaxoSmithKline (GSK), Pfizer, and Moderna in the adult and respiratory vaccine segments.

By integrating HEPLISAV-B and the underlying CpG 1018 platform, Sanofi is not just expanding its adult vaccine footprint—it is also strengthening its capabilities in immunostimulatory technology that could power future vaccine candidates beyond hepatitis B. As the global vaccine market continues to shift toward platforms that prioritize speed, durability, and broad immune activation, synthetic TLR agonists like CpG 1018 may become a central competitive lever in Sanofi’s long-term immunization strategy.

Can Dynavax’s shingles candidate differentiate in a market dominated by GSK?

The more speculative but high-upside element of the deal is Dynavax’s Z-1018 shingles vaccine candidate, currently in phase 1/2 trials. It targets a market where GSK’s Shingrix dominates with a non-live recombinant subunit vaccine using a novel adjuvant system. Z-1018, leveraging the same TLR9 adjuvant platform as HEPLISAV-B, may offer competitive or complementary differentiation—though data on efficacy, tolerability, and dosing remains early-stage.

Shingles, caused by reactivation of the varicella zoster virus, affects one in three adults in their lifetime. The disease burden is particularly high in individuals over 50 and immunocompromised populations, where risk of postherpetic neuralgia and neurological complications is substantial. With Shingrix generating billions in annual sales for GSK, even a moderate market share capture could justify Sanofi’s investment if Dynavax’s candidate can show comparable or superior tolerability, storage, or administration advantages.

How does this deal compare to Sanofi’s recent vaccine and biotech transactions?

Sanofi has been actively reshaping its pipeline through targeted acquisitions and divestments. The company previously announced plans to spin off its consumer healthcare division to focus more aggressively on vaccines, immunology, and oncology. Recent bolt-on acquisitions such as Translate Bio (mRNA), Kadmon (immunology), and Amunix (protein engineering) show a consistent strategy to deepen Sanofi’s proprietary technology and late-stage asset portfolio.

The Dynavax deal fits this pattern. Unlike a high-risk biotech platform bet, this acquisition offers both commercial revenue via HEPLISAV-B and R&D platform expansion via TLR agonist-based vaccines. At a $2.2 billion price tag, Sanofi is paying approximately a 70% premium to Dynavax’s prior market cap, which implies strong internal conviction in both HEPLISAV-B’s long-term growth and Z-1018’s future potential.

The use of available cash also signals capital discipline, with no expected impact on Sanofi’s 2025 financial guidance. That is likely to be well-received by investors, particularly in light of recent pressure on pharmaceutical margins and pipeline productivity across the industry.

Could Dynavax’s vaccine adjuvant platform become a broader asset for Sanofi?

One overlooked aspect of the deal is the strategic value of Dynavax’s adjuvant capabilities. The company’s proprietary CpG 1018 adjuvant, used in both HEPLISAV-B and Z-1018, has demonstrated robust immune potentiation and may offer cross-platform value, particularly in pandemic preparedness scenarios or in enhancing immune responses among older or immunocompromised populations.

While adjuvant platforms are not always headline-grabbing, they are a critical lever for improving vaccine efficacy and durability. Sanofi could explore leveraging CpG 1018 across other candidates in its pipeline, particularly as mRNA and subunit vaccines become more prominent in adult immunization.

This aligns with broader trends in vaccinology, where competitive advantage increasingly hinges on immune response, logistical simplicity, and safety rather than solely on antigen targeting.

What are the remaining risks and milestones to watch in 2026?

The tender offer structure means the transaction still hinges on shareholder acceptance and antitrust review under the Hart-Scott-Rodino Act. While overlap risk is low given the niche product focus, the shingles market dominance by GSK could draw secondary scrutiny depending on future head-to-head trial designs and payer dynamics.

Execution risk exists in scaling HEPLISAV-B globally. Despite U.S. approval and commercial availability, uptake outside the U.S. has lagged. Sanofi’s global commercial footprint may change that trajectory, but physician education, public health partnerships, and market access strategies will determine real-world revenue lift.

Pipeline-wise, investors will be closely watching interim Z-1018 readouts and any expansion of TLR-based formulations in Sanofi’s R&D disclosures. Failure to show efficacy or tolerability advantages over Shingrix could cap the upside of the shingles play.

Key takeaways: What Sanofi’s Dynavax acquisition signals for adult vaccines and platform strategy

• Sanofi’s $2.2 billion acquisition of Dynavax adds a marketed adult hepatitis B vaccine and a phase 1/2 shingles candidate to its portfolio.

• HEPLISAV-B offers a simplified two-dose hepatitis B regimen, a strategic fit in Sanofi’s push into adult immunization.

• The deal provides access to Dynavax’s TLR9-based vaccine adjuvant platform, with potential applications across Sanofi’s pipeline.

• Z-1018, Dynavax’s shingles candidate, targets a multibillion-dollar market currently led by GSK’s Shingrix.

• Sanofi aims to globalize HEPLISAV-B and accelerate the clinical development of Z-1018 using its commercial and R&D scale.

• The acquisition is being funded through cash reserves and is not expected to affect Sanofi’s 2025 financial guidance.

• Integration and regulatory risks remain, particularly around antitrust review and global adoption of HEPLISAV-B.

• The move reinforces Sanofi’s broader strategy of pivoting toward differentiated, platform-based vaccine assets.