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Sanofi's (SNY) agreement to acquire Dynavax (DVAX) for $15.50/share, reflecting a total equity value of approximately $2.2 bln, enhances SNY's adult immunization presence. The deal adds a differentiated, marketed adult vaccine and an emerging shingles program that SNY can potentially scale with its global development infrastructure, manufacturing expertise, and commercial reach, while also helping smooth some of the volatility SNY has faced in seasonal respiratory vaccines.

• The offer price represents an approximate 39% premium to DVAX's Dec. 23 closing price, sending DVAX shares sharply higher. SNY expects to fund the acquisition with available cash and anticipates closing in 1Q26.
• The main appeal is the addition of two core assets, DVAX's adult hepatitis B vaccine HEPLISAV-B and its shingles vaccine candidate Z-1018.
• HEPLISAV-B is marketed in the U.S. and stands out for its two-dose regimen over one month, versus traditional hepatitis B vaccines that are commonly administered as three doses over six months.
• The timing also fits with what SNY noted on its Q3 call in October. Its vaccine segment faced headwinds tied to competitive pricing pressure and softer U.S. flu immunization rates, while management reiterated its focus on advancing and broadening the vaccine portfolio.
• It also disclosed it discontinued its RSV toddler program, underscoring why bolstering the vaccine pipeline remains a priority.
• The deal is not expected to impact SNY's 2025 guidance. Its most recent guidance stands at high single-digit sales growth at CER and an EPS rebound, with low double-digit growth at CER.

Briefing.com Analyst Insight

This seems like a logical addition for SNY's vaccine business. Beyond the headline premium, the strategic rationale is straightforward. HEPLISAV-B gives SNY an established adult product with a differentiated schedule that can be amplified with SNY's scale, while Z-1018 adds longer-dated optionality in the large adult shingles category. Just as importantly, the deal helps diversify SNY's vaccine exposure at a time when the near-term backdrop for seasonal respiratory vaccines has been choppy, reflecting price competition and softer immunization dynamics, and after SNY's RSV toddler discontinuation. Watch items include early commercial execution for HEPLISAV-B under SNY and how management frames development and lifecycle plans for Z-1018. That said, Z-1018 remains in clinical development, so the upside case carries execution and clinical risk.