List of Excipients in Branded Drug ZOSTAVAX

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ZOSTAVAX Excipient Strategy and Commercial Opportunities

Last updated: October 2, 2026

ZOSTAVAX is a live attenuated varicella-zoster vaccine whose commercial value has largely ended in the United States. Merck requested withdrawal of the U.S. license, effective November 18, 2020, and CDC recommendations now favor recombinant Shingrix for herpes zoster prevention.[1,2] The remaining commercial opportunities are therefore concentrated in excipient technology, cold-chain reduction, gelatin-free formulations, contract manufacturing, and international or legacy-market supply rather than in relaunching the original product.

The core formulation opportunity is to preserve live Oka/Merck varicella-zoster virus during lyophilization and reconstitution while reducing excipient-related restrictions. ZOSTAVAX used a stabilizer system based on sucrose, hydrolyzed porcine gelatin, monosodium L-glutamate, phosphate salts, potassium chloride, sodium chloride, and residual-process controls including neomycin.[3]

What is the current FDA regulatory status of ZOSTAVAX?

ZOSTAVAX is no longer marketed in the United States.

Regulatory item	Status
Product	ZOSTAVAX
Active biological component	Live attenuated Oka/Merck varicella-zoster virus
Sponsor	Merck Sharp & Dohme LLC
U.S. regulatory pathway	Biologics license application
U.S. license withdrawal	Effective November 18, 2020
Current CDC preference	Shingrix recombinant zoster vaccine
U.S. routine commercial availability	Discontinued
Generic substitution	Not available through an ordinary ANDA pathway
Biosimilar pathway	Not applicable in the conventional monoclonal-antibody sense

FDA accepted Merck’s request to withdraw the ZOSTAVAX license. The withdrawal was not based on a finding that the product was unsafe or ineffective; the product was displaced commercially by Shingrix and was no longer manufactured for the U.S. market.[1]

ZOSTAVAX may still appear in historical prescribing, vaccination, adverse-event, and patent records. Those records do not indicate current U.S. supply.

What excipients are used in ZOSTAVAX?

The ZOSTAVAX formulation contains a lyophilized live-virus component and a separate sterile diluent. The vaccine is reconstituted before administration.

ZOSTAVAX formulation components

Component	Functional role	Commercial relevance
Sucrose	Primary stabilizer and lyoprotectant	Protects viral particles during freezing and drying
Hydrolyzed porcine gelatin	Stabilizer and protective protein matrix	Creates allergy, religious, and dietary-market restrictions
Monosodium L-glutamate	Stabilizer	Supports viral stability during storage
Sodium phosphate dibasic	Buffering agent	Controls formulation pH
Potassium phosphate monobasic	Buffering agent	Completes phosphate buffer system
Potassium chloride	Ionic-strength adjustment	Supports formulation compatibility
Sodium chloride	Tonicity and ionic-strength adjustment	Common parenteral excipient
Neomycin residue	Manufacturing-process antibiotic residue	Requires labeling and allergy controls
Sterile water	Reconstitution diluent	Enables administration of the lyophilized product

The label identifies hydrolyzed porcine gelatin and residual neomycin as clinically relevant formulation-related materials.[3] ZOSTAVAX is preservative-free. It does not use the AS01B adjuvant system found in Shingrix, and it is not interchangeable with Shingrix.

Which excipients create the largest commercial opportunity?

The strongest opportunity is a gelatin-free, thermostable live zoster vaccine platform. A direct replacement for ZOSTAVAX would require a new clinical and regulatory program, but the underlying excipient technologies can be commercialized across other live viral vaccines.

Gelatin replacement

Hydrolyzed porcine gelatin is the most commercially visible excipient constraint. A replacement program could evaluate:

• Recombinant gelatin
• Fish-derived gelatin
• Plant-derived hydrocolloids
• Recombinant albumin
• Amino-acid and sugar combinations
• Synthetic polymers with low immunogenicity
• Protein-free lyophilization systems

A gelatin-free formulation could expand use in populations with porcine restrictions, gelatin allergy concerns, and markets with religious or cultural limitations. The replacement must preserve infectivity after drying, reconstitution, and refrigerated storage. It must also avoid aggregation, potency loss, altered injection characteristics, and new immunogenicity concerns.

Sugar and amino-acid stabilization

Sucrose and monosodium L-glutamate provide a relatively conventional stabilizer platform. Commercial development could focus on optimizing the ratio of:

• Sucrose or trehalose
• Amino acids
• Polyols
• Phosphate buffer
• Protein or protein-free protective agents

Trehalose may offer an alternative lyoprotectant, but substitution is not automatic. Live varicella-zoster virus is sensitive to process conditions, residual moisture, container closure, reconstitution time, and temperature excursions. A formulation with better laboratory stability still requires potency, sterility, identity, and clinical comparability data.

Protein-free formulations

A protein-free formulation would reduce concerns associated with gelatin and animal-derived materials. It could also simplify global procurement and improve batch-to-batch consistency. The commercial barrier is technical: proteins often provide physical protection to live viral particles during freezing and drying. Replacing them with a fully synthetic system may require a new combination of sugars, amino acids, surfactants, and controlled residual moisture.

How could ZOSTAVAX excipient technology reduce cold-chain costs?

ZOSTAVAX required frozen storage before reconstitution, creating a more demanding logistics profile than many conventional refrigerated vaccines.[3] The original storage requirement limited inventory flexibility and increased the risk associated with transport and pharmacy handling.

A commercial excipient program should target three separate stability endpoints:

1. Frozen storage stability.
2. Refrigerated stability after controlled thawing.
3. Short-term stability after reconstitution.

The highest-value opportunity is a formulation that supports refrigerated storage without loss of viral potency. A second opportunity is increased tolerance to short temperature excursions. A third is a longer post-reconstitution administration window, which could reduce vaccination-site waste.

Potential commercial products include:

• Stabilizer premixes for live viral vaccine manufacturers.
• Lyophilization process packages.
• Container-closure systems optimized for low-residual-moisture products.
• Real-time and accelerated stability testing services.
• Potency-assay platforms for live attenuated zoster vaccines.
• Contract development and manufacturing services for regional vaccine suppliers.

The formulation company would generally monetize through development fees, supply agreements, formulation licenses, or milestone-based arrangements rather than through a direct ZOSTAVAX royalty stream.

What formulation patents protect ZOSTAVAX?

The commercial protection for ZOSTAVAX was likely distributed across product, manufacturing, formulation, and use claims rather than a single excipient patent. The principal protectable categories include:

• Live attenuated Oka/Merck varicella-zoster virus.
• Viral seed lots and biological production methods.
• Stabilized lyophilized vaccine compositions.
• Reconstitution and administration procedures.
• Manufacturing controls for cell-culture propagation.
• Potency and identity testing.
• Packaging and storage configurations.
• Herpes zoster prevention methods.

The key strategic point is that excipient protection is unlikely to recreate the original product franchise by itself. A modern formulation would need freedom to operate around the viral strain, seed-stock controls, manufacturing process, analytical methods, and clinical use claims.

ZOSTAVAX was licensed as a biologic rather than approved as a conventional small-molecule drug. The Orange Book and Paragraph IV framework therefore do not provide the principal route for challenging or substituting the product. A follow-on live vaccine would generally require its own biologics license and supporting clinical package rather than an ordinary abbreviated new drug application.

When did ZOSTAVAX lose exclusivity?

ZOSTAVAX lost practical U.S. commercial exclusivity before it lost all possible intellectual-property relevance.

Event	Commercial significance
2006 U.S. approval	Established the live attenuated zoster-vaccine market
2017 Shingrix approval	Introduced a higher-efficacy recombinant competitor
2018-2019 CDC preference for Shingrix	Accelerated demand shift away from ZOSTAVAX
2020 U.S. license withdrawal	Ended U.S. commercial supply
Post-2020 market	Dominated by Shingrix rather than generic substitution

Shingrix’s stronger efficacy and preferential CDC recommendation substantially reduced the value of maintaining ZOSTAVAX production. CDC states that Shingrix is preferred over ZOSTAVAX for prevention of herpes zoster and related complications in eligible adults.[2]

Patent expiration dates for individual ZOSTAVAX-related families should not be treated as equivalent to market exclusivity. Biological manufacturing know-how, live-virus seed control, regulatory history, and validated potency assays can remain practical barriers after formal patent expiry.

Does ZOSTAVAX face Paragraph IV, generic, or biosimilar competition?

ZOSTAVAX does not present a conventional Paragraph IV generic-entry profile.

Generic competition

A generic manufacturer cannot simply copy the ZOSTAVAX formulation and rely on ordinary small-molecule substitution. A live attenuated vaccine requires control of:

• Viral identity and attenuation.
• Seed-lot genealogy.
• Cell substrate.
• Viral propagation.
• Purification and concentration.
• Lyophilization.
• Potency.
• Genetic stability.
• Sterility and adventitious-agent testing.

These requirements make manufacturing capability and regulatory validation more important than a simple excipient copy.

Biosimilar competition

ZOSTAVAX is a biologic, but it is not a typical biosimilar target. A follow-on developer would face a product-specific regulatory program involving a live virus. The relevant competitive model is an independent vaccine BLA or another applicable biologics pathway, not a direct biosimilar substitution model used for many therapeutic proteins.

Paragraph IV litigation

Paragraph IV litigation is not the central entry mechanism for a discontinued live vaccine. Any patent challenge would need to be assessed against specific unexpired claims and the proposed manufacturing process. The more important barriers are technical reproducibility, clinical development, and regulatory approval.

What commercial opportunities remain for ZOSTAVAX-related excipients?

Excipient licensing

An excipient owner could license a gelatin-free stabilizer system to manufacturers developing:

• Live varicella vaccines.
• Measles, mumps, and rubella vaccines.
• Live influenza vaccines.
• Yellow fever vaccines.
• Other lyophilized viral vaccines.

The strongest licensing position would come from data demonstrating equivalent or superior viral potency, reduced cold-chain sensitivity, and compatibility with existing filling equipment.

Regional vaccine manufacturing

International manufacturers may have an incentive to develop a live zoster vaccine for markets where Shingrix access, pricing, or supply is limited. A lower-cost formulation would need to compete against the clinical and commercial acceptance of Shingrix, not only against the discontinued U.S. ZOSTAVAX product.

A regional product could be commercially viable if it combines:

• Lower manufacturing cost.
• Refrigerated rather than frozen distribution.
• Reduced vial waste.
• Gelatin-free composition.
• Longer stability under temperature excursions.
• A practical local regulatory pathway.

Contract development and manufacturing

CDMOs with live-virus expertise can offer value through process transfer, aseptic filling, lyophilization, analytical validation, and stability programs. This opportunity is more defensible than selling commodity excipients because live-vaccine production requires integrated process knowledge.

Analytical services

Assays for infectious titer, antigen identity, genetic stability, residual host-cell DNA, adventitious agents, and potency after thermal stress can generate recurring service revenue. For live vaccines, analytical capability is often a greater bottleneck than the stabilizer itself.

How does ZOSTAVAX compare with Shingrix?

Attribute	ZOSTAVAX	Shingrix
Vaccine type	Live attenuated virus	Recombinant VZV glycoprotein E
Adjuvant	No AS01B system	AS01B adjuvant system
Storage profile	Frozen product before reconstitution	Refrigerated components before reconstitution
U.S. status	License withdrawn	Current preferred zoster vaccine
Manufacturing challenge	Live-virus propagation and stabilization	Recombinant antigen and adjuvant manufacture
Gelatin issue	Hydrolyzed porcine gelatin in formulation	Different formulation architecture
Follow-on opportunity	Live-vaccine development	Recombinant antigen and adjuvant competition
Current commercial position	Discontinued in U.S.	Market-leading U.S. product

The comparison changes the investment thesis. A company seeking a U.S. zoster-vaccine opportunity should generally prioritize recombinant antigen, adjuvant, delivery, or manufacturing-cost innovation rather than a direct ZOSTAVAX reformulation.

What patent and regulatory risks affect a new ZOSTAVAX-like product?

A new developer would face five main risk categories.

Viral-strain and biological-material rights

The Oka/Merck strain, seed stocks, cell substrate, and biological materials may be subject to contractual, regulatory, or proprietary controls even when individual patent claims have expired.

Manufacturing know-how

Live-virus propagation and lyophilization depend on process parameters that may not be fully disclosed in patents. A developer may need to recreate the process experimentally.

Formulation changes

Replacing gelatin, changing the sugar system, or reducing frozen-storage requirements could alter potency, immunogenicity, reconstitution, and stability. Material changes would likely require comparability and clinical support.

Regulatory classification

A new live attenuated zoster vaccine would require a biologics regulatory strategy. The sponsor could not assume that a formulation-only change would receive an abbreviated approval pathway.

Market displacement

Shingrix has established the current U.S. standard. A new ZOSTAVAX-like vaccine would need a clear advantage in price, access, dosing, storage, or geographic availability.

Which excipient strategy has the highest commercial value?

The highest-value strategy is a platform rather than a ZOSTAVAX-specific copy:

1. Develop a gelatin-free, protein-reduced or protein-free stabilizer system.
2. Demonstrate preservation of live viral potency after lyophilization.
3. Establish refrigerated and excursion-stability data.
4. Validate compatibility with aseptic filling and standard vial systems.
5. Protect the composition and process with composition, use, and manufacturing claims.
6. License the platform across multiple live viral vaccines.

A direct ZOSTAVAX relaunch has limited U.S. value because the product is discontinued and Shingrix is preferred. A broader live-vaccine excipient platform can address a larger market and reduce dependence on one discontinued brand.

Key Takeaways

• ZOSTAVAX is no longer marketed in the United States; FDA withdrawal became effective November 18, 2020.[1]
• Its formulation relied on sucrose, hydrolyzed porcine gelatin, monosodium L-glutamate, phosphate salts, potassium chloride, sodium chloride, and sterile water for reconstitution.[3]
• Gelatin replacement is the clearest excipient opportunity.
• Thermostability and reduced frozen-storage dependence offer the strongest logistics value.
• ZOSTAVAX is not a conventional Paragraph IV or generic-substitution opportunity.
• A follow-on live zoster vaccine would require substantial biological, manufacturing, analytical, and clinical development.
• The best commercial model is a licensed stabilizer and process platform for multiple live viral vaccines.
• Shingrix, not a generic ZOSTAVAX product, defines the current U.S. competitive benchmark.[2]

FAQs About ZOSTAVAX Excipients and Commercial Strategy

Is ZOSTAVAX still available in the United States?

No. Merck withdrew the U.S. license, effective November 18, 2020.[1]

Does ZOSTAVAX contain porcine gelatin?

Yes. The formulation uses hydrolyzed porcine gelatin as a stabilizer.[3]

Can a company sell a generic version of ZOSTAVAX?

Not through the ordinary small-molecule generic pathway. A follow-on live vaccine would require an appropriate biologics approval strategy and independent manufacturing and quality data.

Could a gelatin-free ZOSTAVAX formulation be approved?

Potentially, but replacing gelatin would be a material formulation change requiring evidence that potency, stability, safety, and immunogenicity remain acceptable.

Is ZOSTAVAX a biosimilar opportunity?

Not in the conventional sense. Its follow-on commercial pathway would be more complex than biosimilar development for a well-characterized therapeutic protein.

References

1. U.S. Food and Drug Administration. (2020). Zostavax vaccine, live: Withdrawal of approval of biologics license application. Federal Register.

2. Centers for Disease Control and Prevention. (2024). Shingles vaccination: What everyone should know. U.S. Department of Health and Human Services.

3. Merck Sharp & Dohme LLC. (2019). ZOSTAVAX [package insert]. U.S. Food and Drug Administration.