The pandemic made vaccines noisy. This acquisition is a bet that the best vaccine businesses are, in fact, boring: repeatable demand, defensible distribution, and a long runway for “catch-up” shots.
When vaccine markets make headlines these days, it is often for the wrong reasons: shortages, politics, or the whiplash of post-pandemic demand. But Sanofi’s agreement to buy Dynavax for about $2.2bn suggests a different story is taking shape — one that looks less like crisis medicine and more like consumer staples.
Sanofi will pay $15.50 per share in cash for Dynavax, a 39 per cent premium to the prior close, and expects to close the deal in Q1 2026, funded from existing cash. The prize is not a moonshot platform or a shiny new modality. It is something far more practical: a marketed adult hepatitis B vaccine with a simpler schedule — and a potential challenger to the world’s dominant shingles shot.
This matters because adult immunisation is quietly becoming one of the most defensible corners of pharma. The moat is built less on patents and more on behaviour: convenience, completion, and the everyday plumbing of healthcare — pharmacies, clinics, reimbursement codes, and a clinician’s muscle memory.
The assets: a faster hepatitis B vaccine — and a shingles challenger
Dynavax’s commercial engine is HEPLISAV-B, an adult hepatitis B vaccine known for its two-dose regimen over one month, compared with older schedules that typically require three doses over six months.
Sanofi is also buying Dynavax’s pipeline, led by Z-1018, a shingles vaccine candidate now in Phase 1/2. Early clinical data presented by Dynavax suggest Z-1018 can generate antibody and CD4+ T-cell responses comparable to Shingrix, with a more tolerable reactogenicity profile — a direct attempt to compete on the one feature many patients remember most: how rough they feel after the shot.
For Sanofi, the combination is strategically neat. HEPLISAV-B adds an adult “workhorse” vaccine that can be sold year-round. Z-1018 adds upside in a category where the incumbent is large and profitable.
Why hepatitis B is still a growth market in rich countries
Hepatitis B sounds like a solved problem because newborn vaccination has been a global public health success. Yet adult coverage remains patchy — and that gap is now the commercial opportunity.
Sanofi points to a startling US fact: nearly 100 million adults born before 1991 remain unvaccinated, many potentially at risk. On the public health side, hepatitis B remains a global killer. The World Health Organization estimates 254 million people were living with chronic hepatitis B in 2022, with 1.2 million new infections each year.
In the US, policy has been moving toward closing the adult gap. The CDC’s Advisory Committee on Immunization Practices now recommends universal hepatitis B vaccination for adults aged 19–59, and vaccination for older adults with risk factors (with optional vaccination for those 60+ without known risk factors). The direction of travel is clear: make adult vaccination simpler to prescribe, easier to remember, and less dependent on a clinician guessing who is “high risk”.
But recommendation is not the same as completion. That is where Dynavax’s product design becomes commercial strategy.
The “two-dose advantage” is not marketing — it is maths
In vaccine markets, the best product is often the one patients actually finish. The difference between two and three doses is not a rounding error; it is a drop-off cliff.
A large real-world cohort study published in JAMA Network Open found that 45 per cent of adults who started a two-dose hepatitis B series completed it, compared with 26 per cent for those who started a three-dose series. That gap is not just clinical. It is revenue.
The logic is straightforward:
- A shorter schedule improves the odds that the second appointment happens.
- Higher completion increases true population protection (and reduces downstream costs).
- Better completion rates are easier to sell to health systems that are judged on quality metrics.
The biology supports the positioning. Dynavax’s vaccine uses a TLR9 agonist adjuvant (CpG) designed to boost immune response, and clinical reviews have reported higher seroprotection rates versus older comparators in multiple studies, particularly in harder-to-vaccinate adult groups.
This is why HEPLISAV-B has been building commercially even without a pharma giant behind it. Dynavax reported $268m in HEPLISAV-B net product revenue in 2024, and guided to $305m–$325m for 2025. In Q3 2025, HEPLISAV-B net product revenue was $90m, up 13 per cent year-on-year.
Sanofi is not buying a stagnant asset. It is buying a growing one — and, crucially, one that could grow faster in a larger commercial machine.
Adult vaccines as “infrastructure”, not campaigns
The best way to understand the strategic appeal is to compare adult vaccines with more volatile parts of pharma.
Many drug categories depend on specialist prescribing, shifting guidelines, and payer negotiations that can change overnight. Adult vaccines are different. They increasingly run through repeatable channels: retail pharmacy chains, employer clinics, and routine primary care. The business is built on logistics, access, and habit.
This is why adult immunisation can behave like infrastructure:
- Distribution is entrenched. Pharmacies have invested in cold chain, training, and workflow.
- Reimbursement is codified. Vaccines fit into established billing systems and preventive benefits.
- Demand is demographically driven. Ageing populations and chronic disease push uptake over time, even when sentiment is noisy.
And adult uptake is still far from “done”. CDC data show hepatitis B vaccination coverage among US adults aged 19+ was 34.2 per cent in 2021. Shingles coverage is also a reminder of how long these curves can take: CDC’s AdultVaxView reports that, among adults aged 50+, coverage with two doses of recombinant zoster vaccine increased to 18.1 per cent by 2022 — still leaving huge headroom.
This is the paradox of adult immunisation. The science can be excellent, the burden real, and yet uptake can lag for years. For a company with patience — and scale — that lag is not failure. It is runway.
Why shingles is the real upside (and the real risk)
If HEPLISAV-B is the dependable base, Z-1018 is the optionality.
Shingles is common and miserable. The CDC estimates about one in three people in the United States will develop shingles in their lifetime. The market is also proven: GSK’s Shingrix continues to produce blockbuster sales, with £0.8bn in Q3 2025 revenue, up 13 per cent year-on-year, according to the company.
So what is the opening for a competitor?
Shingrix is highly effective, but many patients and clinicians are familiar with its reactogenicity. Dynavax’s pitch is that it can match the immune response while making the experience easier. In its Phase 1/2 head-to-head work, Dynavax has said Z-1018 showed comparable antibody and T-cell responses with a favourable tolerability profile, and it has moved the programme forward into an older cohort.
If those signals hold up in larger trials, Sanofi would have something valuable: a credible second entrant in a category where “good enough” is not the bar — the bar is “as good as Shingrix, but easier to take”.
But this is also where investors should keep their discipline. Z-1018 is still early. Phase 1/2 is a long distance from registration, manufacturing scale, and real-world effectiveness. Many vaccine candidates look clean in small studies and then run into the hard realities of larger populations, rarer adverse events, and the messy variability of immune response in older adults.
Sanofi’s deal structure reflects that balance. At $2.2bn, this is meaningful but not existential for a company of Sanofi’s size — the kind of transaction that can pay off handsomely if the pipeline works, and still make sense if only the marketed asset delivers.
Why Sanofi, and why now?
Sanofi has been leaning into vaccines as a growth engine — not just as legacy business. In its 2024 results, the company highlighted vaccines momentum and reported vaccines sales up 10.8 per cent to €2.2bn in Q4 2024, driven in part by its RSV antibody Beyfortus rollout. Yet even strong vaccine companies face volatility: Sanofi’s vaccines sales fell 7.8 per cent to €3.4bn in Q3 2025, largely due to lower influenza sales.
That volatility is the point. Influenza is seasonal and sensitive to timing. Adult hepatitis B is steadier — and, with universal adult recommendations, structurally expanding.
The acquisition also gives Sanofi a chance to do what big pharma often does best: globalise. Dynavax notes that HEPLISAV-B is approved not only in the US but also in the EU and the UK. A company with Sanofi’s commercial reach may be better positioned to widen access, negotiate tender dynamics, and push uptake through systems that are less fragmented than the US.
There is also a more subtle strategic layer. Vaccines are in the middle of a public trust debate, but much of the political heat has focused on childhood immunisation. Adult vaccines — especially those tied to ageing, chronic disease, and cancer prevention — can be easier to frame as personal risk management rather than a cultural battleground. That does not remove the trust problem. But it changes the terrain.
The real moat is operational: making prevention “automatic”
The adult vaccine opportunity is not just scientific. It is operational.
Many adults do not have a “medical home”. They see doctors less frequently. They move between employers and insurance plans. They skip follow-ups. That is why, in practice, the most powerful innovation can be convenience: fewer visits, shorter schedules, and pharmacy-friendly delivery.
HEPLISAV-B fits that logic. So does the broader adult immunisation trend: a growing share of vaccination is happening in retail settings, where speed and simplicity win.
If you want a thought experiment, consider what would happen if adult vaccines became as frictionless as contactless payment — not because people suddenly became more health-conscious, but because the system stopped asking them to do hard things. Two visits instead of three. A month instead of six. A prompt in a pharmacy app. A quality metric that nudges clinics to offer the shot before you leave.
That is the “boring” advantage Sanofi is buying.
What to watch next
Three milestones will tell us whether this deal becomes a template for the next phase of vaccine consolidation:
- Close and integrate (Q1 2026). The transaction is expected to close in the first quarter of 2026, subject to customary conditions.
- Accelerate HEPLISAV-B through new channels. Watch whether Sanofi can expand adult hepatitis B vaccination beyond traditional physician offices and into scaled pharmacy and employer settings.
- See if Z-1018 can stay “Shingrix-comparable” in older adults. Dynavax has initiated later parts of its Phase 1/2 work, including older cohorts. The key will be whether tolerability advantages survive bigger numbers — and whether the immune response remains strong where it matters most.
Sanofi’s Dynavax bet is a reminder that biotech’s most interesting stories are not always about brand-new science. Sometimes they are about the second-order effect of making healthcare easier to finish.
In a market that has become addicted to novelty, adult vaccines are attractive precisely because they are repetitive. They reward execution. They reward scale. And, when they work, they quietly reduce disease without asking for much attention at all.
