Sanofi to acquire Dynavax for $2.2B to scale adult vaccine portfolio

Sanofi (NASDAQ:SNY) has reached a definitive agreement to acquire vaccine specialist Dynavax Technologies (NASDAQ:DVAX) for $15.50 per share in cash, the companies announced Wednesday.

The $2.2 billion transaction represents a 39% premium to Dynavax’s closing price on December 23, 2025, and marks Sanofi’s most significant move to date in consolidating the multi-billion-dollar adult immunization market.

The acquisition centers on HEPLISAV-B®, the only FDA-approved adult hepatitis B vaccine that provides full protection in a two-dose, one-month regimen.

By contrast, traditional vaccines require three doses over six months, a timeline where patient compliance often falters.

By integrating HEPLISAV-B into its massive global commercial infrastructure, Sanofi aims to capture a dominant share of a U.S. market expected to exceed $900 million by 2030.

Beyond the immediate revenue from HEPLISAV-B, the deal provides Sanofi with Z-1018, a Phase 1/2 shingles vaccine candidate.

Recent topline data showed Z-1018 produced an immune response comparable to the current market leader, Shingrix®, but with a significantly more favorable tolerability profile—reporting only 12.5% local reactions compared to over 50% for the incumbent.

The $2.2 billion purchase price will be funded entirely from Sanofi’s existing cash reserves.

The transaction, which has received unanimous approval from the Dynavax Board of Directors, is structured as a tender offer expected to close in the first quarter of 2026.