Sanofi to Buy Dynavax for $2.2bn, Boosts Vaccine Pipeline

French drugmaker Sanofi has agreed to buy U.S.-based biotech firm Dynavax Technologies for about $2.2 billion (around 1.9 billion euros), a move aimed at strengthening its vaccine business and securing new growth drivers for the next decade.

Under the terms of the deal, Sanofi will pay $15.50 per Dynavax share, representing a premium of roughly 39% over the company’s closing price on Tuesday. Following the announcement, Dynavax shares surged nearly 39% in U.S. trading, while Sanofi shares slipped slightly, ending the day down 0.7%.

Strategic Push Amid Vaccine Policy Shifts

Industry analysts say the acquisition comes at a critical time for vaccine makers, particularly in the United States, where immunisation policy is under renewed scrutiny. Changes being shaped by U.S. Health Secretary Robert F. Kennedy Jr. have raised uncertainty around childhood vaccination programmes, prompting drugmakers to look more closely at adult vaccines and alternative growth areas.

The Trump administration recently dropped a long-standing recommendation for universal hepatitis B vaccination in infants, a decision that drew strong criticism from medical professionals. Further changes to immunisation guidelines are also being considered for 2026, adding to regulatory uncertainty.

Against this backdrop, analysts view Dynavax’s portfolio as a good fit for Sanofi. William Blair analyst Matt Phipps said the deal made strategic sense given “growing regulatory concerns around vaccines,” adding that Sanofi lacked an adult hepatitis B or shingles programme before this acquisition.

Heplisav-B Strengthens Adult Vaccine Offering

A key asset in the deal is Dynavax’s hepatitis B vaccine, Heplisav-B. The shot is approved for adults aged 18 and older and is administered in just two doses over one month. This compares favourably with competing hepatitis B vaccines that typically require three doses over six months.

Heplisav-B generated $90 million in sales in the third quarter of 2025 alone. Analysts estimate that peak annual U.S. sales could reach around $609 million, underlining its importance as a long-term revenue contributor for Sanofi.

Phipps noted that the price paid by Sanofi was still below his estimated value of $2.6 billion for Heplisav-B alone, suggesting potential upside if the product continues to gain market share.

Shingles Vaccine Could Deliver Long-Term Growth

The acquisition also brings Dynavax’s experimental shingles vaccine, Z-1018, into Sanofi’s pipeline. While still in development, early trial data has been encouraging. In a study involving 92 people aged between 50 and 69, the vaccine produced an immune response comparable to the market leader while showing a potentially better safety profile.

J.P. Morgan analysts believe Z-1018 could support Sanofi’s revenues beyond 2030 if its early safety and efficacy results are confirmed in larger trials. The shingles market remains highly attractive, currently dominated by GSK’s Shingrix, which is on track to generate around 4 billion euros in sales this year.

Filling the Gap Before Dupixent Patent Expiry

Sanofi has been actively reshaping its product portfolio as it prepares for the loss of patent protection on its blockbuster asthma drug Dupixent in 2031. In recent months, the company has made several strategic moves, including the $1.5 billion acquisition of British vaccine developer Vicebio and an agreement worth up to $9.5 billion to buy Blueprint Medicines.

The Dynavax deal will be funded using Sanofi’s existing cash reserves. The company said it expects the transaction to close in the first quarter of 2026 and confirmed that the acquisition will not affect its financial outlook for 2025.

Vaccine Makers Face Market Pressure

The deal comes as vaccine manufacturers face broader challenges. Earlier this year, Sanofi and GSK both highlighted pressure in the U.S. flu vaccine market. Australian biotech CSL has also delayed plans to spin off its vaccine unit, citing increased volatility and a sharper-than-expected drop in U.S. immunisation rates.

FDA Setback in Multiple Sclerosis Programme

Separately, Sanofi disclosed that the U.S. Food and Drug Administration has declined to approve its experimental multiple sclerosis drug, tolebrutinib, intended to slow disability progression in certain patients.

Houman Ashrafian, Sanofi’s head of research and development, said the decision was unexpected, as the company had previously been told that the FDA review would continue into early 2026. He described the move as a “significant and meaningful change in direction” from earlier feedback.

The setback adds to a challenging year for Sanofi, following disappointing data from experimental treatments for eczema and smoking-related lung disease. As a result, the company’s shares have lagged the broader European healthcare index.

Despite these challenges, analysts say the Dynavax acquisition gives Sanofi a stronger and more diversified vaccine pipeline, positioning the company to navigate regulatory shifts and sustain growth in the years ahead.