Sanofi agreed to acquire Dynavax Technologies for $2.2 billion in cash, closing a deal that brings Heplisav‑B into Sanofi’s commercial vaccine portfolio and adds a clinical-stage shingles candidate. The deal values Dynavax at a ~39% premium to its prior close and consolidates Sanofi’s position in prophylactic vaccines. Sanofi will integrate Dynavax’s manufacturing and commercial capabilities for hepatitis B while advancing the shingles candidate through clinical development. Investors and competitors will watch how Sanofi leverages the acquisition to expand market share versus GSK in adult vaccines. The transaction represents one of the larger vaccine deals of 2025 and signals continued M&A activity among Big Pharma to fill vaccine pipelines with marketed products plus near-term development assets.