A Comprehensive Monograph on ADT™ Booster (Diphtheria and Tetanus Vaccine, Adsorbed; Seqirus)

I. Executive Summary

ADT™ Booster is a combined, adsorbed vaccine providing booster immunization against diphtheria and tetanus. Sponsored in Australia by Seqirus Pty Ltd, a subsidiary of CSL, and manufactured by AJ Vaccines A/S in Denmark, this vaccine is formulated with reduced antigen content, specifically for re-vaccination purposes. Its primary indication is for children aged five years and older and adults who have previously completed a primary immunization course against both diseases. The vaccine is not intended for primary immunization. Each 0.5 mL dose contains no less than 2 International Units (IU) of diphtheria toxoid and no less than 20 IU of tetanus toxoid, adsorbed onto an aluminium hydroxide adjuvant to enhance immunogenicity.

The vaccine's mechanism of action is based on the well-established principle of toxoid-induced immunity, whereby it stimulates the production of neutralizing antibodies against the toxins produced by Corynebacterium diphtheriae and Clostridium tetani, rather than the bacteria themselves. The clinical efficacy of diphtheria and tetanus toxoids is not derived from modern, large-scale clinical trials, which would be unethical to conduct. Instead, efficacy is inferred from decades of epidemiological data and the consistent achievement of seroprotective antitoxin levels in vaccinated individuals. A complete primary series is considered to confer near-universal protection.

The safety profile of ADT™ Booster is well-characterized and consistent with other tetanus and diphtheria toxoid vaccines. The most common adverse reactions are transient, self-limiting local injection site reactions (pain, redness, swelling) and mild systemic effects such as fever and malaise. Serious adverse events, including anaphylaxis, are rare. Specific precautions are noted for individuals with hypersensitivity to vaccine components, including the natural rubber latex present in the pre-filled syringe tip cap.

ADT™ Booster holds regulatory approval from the Australian Therapeutic Goods Administration (TGA) and is listed on the Pharmaceutical Benefits Scheme (PBS), solidifying its role in the national immunization program. However, the product is not licensed for use in major international markets such as the United States or Europe, where Seqirus's commercial focus is predominantly on its portfolio of influenza vaccines. This positions ADT™ Booster as a legacy public health product maintained by Seqirus to fulfill its long-standing commitment to Australia's national health interests. While the product label and conventional guidelines recommend a 10-year booster interval, this report highlights a significant and growing body of scientific evidence suggesting that immunity may persist for 30 years or longer, prompting a critical need for public health authorities to re-evaluate adult booster schedules.

II. Product Identification and Pharmaceutical Formulation

A. Product Nomenclature and Regulatory Identification

The precise identification of a biological product is critical for regulatory tracking, pharmacovigilance, and correct clinical application. The Diphtheria/Tetanus Toxoid combined vaccine sponsored by Seqirus is identified as follows:

• Proprietary Name: ADT™ Booster [1]
• Non-proprietary/Common Name: Diphtheria and Tetanus Vaccine (adsorbed) for re-vaccination [1]
• Sponsor: The sponsor and distributor in Australia is Seqirus Pty Ltd, a key part of the CSL Group, a global biotechnology company with deep roots in Australian public health.[1]
• Manufacturer: The vaccine is manufactured by AJ Vaccines A/S, located at 5, Artillerivej, DK-2300 Copenhagen S, Denmark.[1] The distinction between the Australian sponsor and the Danish manufacturer points to a specific supply chain model where Seqirus leverages an external partner for the production of this non-influenza vaccine, which differs from its in-house manufacturing of influenza vaccines at its facilities in the US, UK, and Australia.[7]
• Australian Regulatory Information:
• Therapeutic Goods Administration (TGA) ARTG ID: 130919 [1]
• Australian Register of Therapeutic Goods (AUST R) Numbers: 130906, 130919 [1]
• Pharmaceutical Benefits Scheme (PBS) Item Codes: The vaccine is listed on the PBS, ensuring subsidized access. It is available under item code 3463G for the Prescriber Bag (emergency drug supply) and 8783G for the General Schedule.[2]

B. Composition and Formulation

Each 0.5 mL dose of ADT™ Booster is a sterile suspension containing the following components, each with a specific function in generating a protective immune response.[1]

• Active Ingredients: The immunologically active components are purified, inactivated bacterial toxins (toxoids).
• Purified Diphtheria Toxoid: No less than 2 International Units (IU). This is a reduced quantity appropriate for a booster dose.
• Purified Tetanus Toxoid: No less than 20 International Units (IU).
• Adjuvant: An adjuvant is included to enhance the immune response to the toxoids.
• Aluminium hydroxide hydrate: Corresponds to 0.5 mg of aluminium. This substance acts as an adsorbent, creating a depot at the injection site that prolongs antigen presentation to immune cells, thereby increasing the magnitude and durability of the antibody response.
• Excipients: These are inactive ingredients that serve as the vehicle for the active components.
• Sodium chloride: 4 mg.
• Sodium hydroxide: Used to adjust the pH to approximately 7.0.
• Water for Injections: Serves as the solvent.
• Manufacturing Residuals and Material Information:
• Formaldehyde: Trace amounts may be present as a residual from the toxoid inactivation process. This necessitates a precaution for individuals with known formaldehyde hypersensitivity.[1]
• Bovine-Derived Materials: The manufacturing process includes exposure to materials of bovine origin. The product information includes a standard regulatory statement noting that no evidence exists linking any vaccine product to cases of variant Creutzfeldt-Jakob disease (vCJD).[1]
• The vaccine formulation contains no preservatives (such as thimerosal) and no ingredients of human origin.[1]

C. Pharmaceutical Form, Appearance, and Presentation

• Form: The vaccine is a suspension for intramuscular injection.[1]
• Appearance: Prior to administration, the vaccine should appear as a suspension of white and grey particles in a colourless or light yellow fluid. It is imperative that the vial or syringe be thoroughly shaken before use to ensure adequate dispersion of the adsorbed toxoids, as failure to do so could result in suboptimal dosage and immunogenicity.[1]
• Packaging and Presentation:
• ADT™ Booster is supplied in single-use 0.5 mL formats, either in a needle-less pre-filled syringe or a vial made of Type 1 glass.[1]
• Available pack sizes are 1 x 0.5 mL and 5 x 0.5 mL.[1]
• A critical safety detail relates to packaging components: the tip cap of the pre-filled syringe contains natural rubber latex. This is a direct driver of a specific warning for individuals with latex allergies. The syringe barrel, plunger rod, plunger stopper, vial, and vial stopper are all latex-free.[1] This level of detail reflects modern regulatory requirements to identify and mitigate all potential sources of allergic reactions.

Table 1: Vaccine Composition Summary

Component Type	Substance	Quantity per 0.5 mL Dose	Function/Note
Active Ingredient	Purified Diphtheria Toxoid	≥2 IU	Stimulates anti-diphtheria toxin antibody production 1
Active Ingredient	Purified Tetanus Toxoid	≥20 IU	Stimulates anti-tetanus toxin antibody production 1
Adjuvant	Aluminium hydroxide hydrate	Corresponds to 0.5 mg aluminium	Enhances and prolongs the immune response 1
Excipient	Sodium chloride	4 mg	Isotonic agent 8
Excipient	Sodium hydroxide	q.s. to pH 7	pH adjuster 8
Excipient	Water for Injections	q.s. to 0.5 mL	Vehicle/Solvent 8
Manufacturing Residual	Formaldehyde	Trace amounts	Residual from toxoid inactivation process 8
Packaging Component	Natural Rubber Latex	Present in syringe tip cap only	Potential allergen; not present in vial presentation 1

III. Pharmacological Profile and Mechanism of Action

A. Pathogenesis of Diphtheria and Tetanus

Understanding the mechanism of action of ADT™ Booster requires an appreciation of the diseases it prevents. Both diphtheria and tetanus are toxin-mediated diseases, meaning their severe clinical manifestations are caused by potent exotoxins produced by the causative bacteria, not by the bacteria themselves.

• Diphtheria: This disease is caused by infection with toxin-producing strains of Corynebacterium diphtheriae, a gram-positive bacillus transmitted via respiratory droplets or close contact.[9] The bacteria colonize the upper respiratory tract, where they produce diphtheria toxin. This toxin causes local tissue necrosis, leading to the formation of a characteristic grey-colored pseudomembrane that can adhere to the tonsils, pharynx, or larynx, potentially causing airway obstruction. If the toxin enters the bloodstream, it can cause severe systemic complications, including myocarditis (inflammation of the heart muscle) and neuropathy.[9] The toxin's "Fragment A" is a potent enzyme that blocks protein synthesis, leading to cell death, while "Fragment B" is responsible for binding to host cells.[10]
• Tetanus: Commonly known as lockjaw, tetanus is an infectious but non-communicable disease caused by the neurotoxin produced by the gram-positive, spore-forming bacillus Clostridium tetani.[9] The spores are ubiquitous in soil and can enter the body through breaches in the skin, such as puncture wounds or cuts.[9] In the anaerobic environment of a wound, the spores germinate and the bacteria produce tetanospasmin, one of the most potent neurotoxins known.[10] The toxin travels via peripheral nerves to the central nervous system, where it acts presynaptically to block the release of inhibitory neurotransmitters. This interference results in unopposed motor neuron activity, leading to generalized muscle rigidity and severe, painful convulsive spasms that can be strong enough to cause bone fractures.[9] Death can result from respiratory failure. Because the source of infection is environmental, herd immunity provides no protection against tetanus; immunity can only be achieved through individual vaccination.[11] This epidemiological feature makes personal immunization the sole public health strategy for tetanus prevention.

B. Immunological Mechanism of Toxoid Vaccines

ADT™ Booster is a toxoid vaccine, a class of vaccines that induces immunity against the pathogenic toxins rather than the microorganisms that produce them. The mechanism is a highly specific and elegant immunological strategy.

1. Induction of Active Immunity: The vaccine contains diphtheria and tetanus toxins that have been rendered non-toxic (detoxified), typically with formaldehyde, to create "toxoids".[9] These toxoids retain their antigenic structure, allowing the immune system to recognize them as foreign, but they cannot cause disease.
2. Antibody Production: Upon intramuscular injection, the toxoids are processed by antigen-presenting cells. This initiates an active immune response, stimulating B-lymphocytes to differentiate into plasma cells that produce neutralizing antibodies (antitoxins) specific to the diphtheria and tetanus toxins.[1]
3. Establishment of Immunological Memory: The primary immune response also generates long-lived memory B-cells and T-cells. These cells persist in the body, providing the basis for a rapid and robust secondary immune response upon subsequent exposure.
4. Mechanism of Protection: If a vaccinated individual is later exposed to C. diphtheriae or C. tetani, the bacteria may still colonize or infect a wound. However, as they begin to produce toxins, the pre-existing, vaccine-induced circulating antitoxin antibodies rapidly bind to and neutralize the toxins.[10] This prevents the toxins from reaching their target receptors on host cells (e.g., cardiac cells for diphtheria toxin, neurons for tetanus toxin), thereby averting the clinical signs and symptoms of the disease. Protective antibodies against diphtheria are directed against the toxin's "Fragment B," preventing its entry into cells.[10]

C. Role of the Adjuvant

The formulation of ADT™ Booster includes aluminium hydroxide as an adjuvant.[1] Adjuvants are substances that enhance the immunogenicity of antigens. The aluminium salt adsorbs the diphtheria and tetanus toxoids, creating a depot effect at the site of injection. This slows the release of the antigens and helps to recruit and activate antigen-presenting cells, leading to a more potent and durable immune response than would be achieved with the toxoids alone.[13] The use of an adjuvant is critical for the effectiveness of inactivated vaccines like ADT™ Booster.

D. Pharmacodynamics and Expected Duration of Protection

Following the intramuscular administration of ADT™ Booster, the intended pharmacodynamic effect is the stimulation of the immune system to produce protective levels of antitoxin antibodies.[1] The product information for ADT™ Booster states that protection against diphtheria and tetanus can be expected to last for up to 10 years after a booster dose is administered.[1] This duration forms the basis for the conventional decennial booster recommendation in many national immunization schedules.

IV. Clinical Application and Administration Guidelines

A. Therapeutic Indications and Target Populations

ADT™ Booster has a specific and narrowly defined clinical indication. It is intended for re-vaccination (booster immunization) against diphtheria and tetanus.[1]

• Target Population: The vaccine is approved for use in children aged 5 years and older (≥ 5 years) and adults.[1]
• Prerequisite: A critical condition for its use is that the individual must have previously received at least three doses of a vaccine for primary immunization against diphtheria and tetanus.[1]
• Exclusion: The product information explicitly and repeatedly states that ADT™ Booster is not intended for primary immunization.[1] This is a crucial instruction rooted in the vaccine's formulation. Primary immunization requires higher antigen doses (particularly for diphtheria, designated as 'D' in DTaP) to build immunity from a naive state. Booster vaccines like ADT™ Booster contain a reduced dose of diphtheria toxoid ('d' or 'dT') sufficient to elicit a memory response in a primed immune system while minimizing the risk of severe local hypersensitivity (Arthus) reactions that can occur with high antigen doses in individuals with pre-existing antibodies.[10] Using a low-dose booster for a primary series could result in an inadequate immune response and vaccine failure.

The use of ADT™ Booster should align with official national recommendations, such as those outlined in The Australian Immunisation Handbook.[1] This handbook recommends a booster dose of a tetanus-toxoid containing vaccine for adolescents aged 11-13 years and for adults at age 50, and again for those aged 65 years or older if more than 10 years have passed since their last dose.[15] ADT Booster is one of the registered options for these booster doses.

B. Dosage, Scheduling, and Method of Administration

• Dosage: The standard dose is 0.5 mL.[1]
• Route of Administration: The vaccine must be administered via the intramuscular (IM) route.[1] The deltoid muscle of the upper arm is the preferred site for adults and older children.[13]
• Preparation: As an adsorbed suspension, the vaccine must be shaken thoroughly immediately before administration to ensure a uniform distribution of the vaccine components and to guarantee the correct dosage of antigens is delivered.[1]
• Single Use: ADT™ Booster is for single use in one patient only. Any remaining residue in the vial or syringe must be discarded.[1]

C. Contraindications and Use in Special Populations

• Absolute Contraindications:
• A history of a serious allergic reaction (e.g., anaphylaxis) to a previous dose of ADT™ Booster or any other vaccine containing diphtheria or tetanus toxoids.[1]
• Known hypersensitivity to any component of the vaccine, including the active ingredients, excipients, or manufacturing residuals like formaldehyde.[1]
• Special Populations:
• Pregnancy (Category A): The Australian TGA has assigned ADT™ Booster to Pregnancy Category A. This category is for drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.[1] This high safety rating is likely based on decades of extensive historical use of Td vaccines in pregnant women globally, primarily to prevent neonatal tetanus. The product information advises that during pregnancy, the potential risk of clinical infection should be weighed against the theoretical risks of vaccination.[1]
• Lactation: There is no evidence to suggest that administering ADT™ Booster to a breast-feeding mother is harmful to the infant.[1]
• Immunocompromised Individuals: For individuals with a compromised immune response, whether due to disease or immunosuppressive therapy, the serological response to the vaccine may be impaired or reduced. Vaccination can still proceed, but the level of protection achieved may be suboptimal.[8]
• Pediatric Use: The vaccine is not indicated for use in children under 5 years of age.[6]
• Geriatric Use: The official product information states that no specific data are available for use in the elderly population.[8]

V. Safety and Tolerability Profile

The safety profile of ADT™ Booster is well-established and consistent with the known reactogenicity of adsorbed diphtheria and tetanus toxoid vaccines. The majority of adverse events are mild, transient, and represent the expected inflammatory response to vaccination.

A. Common and Systemic Adverse Reactions

Based on the product information, the following adverse reactions have been reported.[1]

• Most Common Reactions: The most frequently reported adverse events are local reactions at the injection site and systemic pyrexia. These typically manifest within 48 hours of vaccination.
• Local Reactions: Redness, swelling, and pain at the injection site.
• Systemic Reactions: Fever.
• Other Systemic Reactions: A range of other systemic effects have been reported for this type of vaccine, including:
• General: Pruritus (itching), rash, urticaria (hives), peripheral oedema (swelling of extremities).
• Hypersensitivity: Anaphylactoid and hypersensitivity reactions.
• Constitutional: Flu-like symptoms, which may include headache, rigors (shivering), asthenia (weakness), fatigue, and myalgia (muscle pain).
• Gastrointestinal: Nausea, vomiting, and dizziness.[1]

Table 2: Summary of Adverse Reactions by Frequency

The following table, derived from the product information, categorizes reported adverse drug reactions by organ system and frequency.[1]

Organ System Class	Frequency Category	Specific Adverse Reaction
Immune system disorders	Rare (>1/10,000 and <1/1,000)	Anaphylactic reactions
Skin and subcutaneous tissue disorders	Uncommon (>1/1,000 and <1/100)	Eczema, dermatitis, urticarial reactions
General disorders and administration site conditions	Common (>1/100 and <1/10)	Malaise, fever ≥38∘C, redness/swelling at the injection site
	Uncommon (>1/1,000 and <1/100)	Redness/swelling ≥6 cm at the injection site
	Rare (>1/10,000 and <1/1,000)	High fever >40∘C, granuloma or sterile abscess at the injection site

B. Special Warnings, Precautions, and Potential for Serious Events

Beyond common side effects, several important warnings and precautions must be observed to ensure the safe administration of ADT™ Booster.

• Anaphylaxis: Although rare, severe allergic reactions can occur with any injectable vaccine. Therefore, appropriate medical treatment, including epinephrine (adrenaline) injection, and supervision should always be immediately available whenever the vaccine is given.[1]
• Arthus-Type Hypersensitivity: The product information warns that too-frequent booster vaccinations will increase the risk of adverse reactions.[1] This specifically refers to the potential for severe local reactions, known as Arthus reactions. These are Type III hypersensitivity reactions caused by the formation of immune complexes between the injected vaccine antigens and high levels of pre-existing circulating antibodies in the recipient. This leads to local inflammation, severe pain, extensive swelling, and induration.[10] This immunological phenomenon is the primary reason why booster doses are not recommended more frequently than every 10 years in standard practice.
• Management of Acute Illness: Vaccination should generally be postponed in individuals with moderate or severe acute illness, with or without fever. However, mild common illnesses are not considered a contraindication to vaccination.[1]
• Neurological Events: The potential for postvaccinal neurologic disorders must be considered. While extremely rare, events such as hypoesthesia (reduced sensation), paraesthesia (abnormal sensation), and brachial radiculitis (inflammation of nerve roots in the arm) have been reported following the injection of biological products.[1] Furthermore, a causal relationship between tetanus toxoid-containing vaccines and Guillain-Barré Syndrome (GBS) has been established by the Institute of Medicine.[16] The decision to vaccinate an individual who previously experienced GBS within six weeks of a tetanus-containing vaccine requires careful consideration of the benefits and risks.[16] The inclusion of these warnings reflects the comprehensive nature of modern pharmacovigilance, which incorporates rare signals detected from post-marketing surveillance across millions of administered doses.
• Manufacturing-Related Precautions:
• Formaldehyde Hypersensitivity: Caution should be exercised in subjects with a known hypersensitivity to formaldehyde, as trace amounts may be present in the final product from the manufacturing process.[1]
• Latex Allergy: The pre-filled syringe presentation has a tip cap that contains natural rubber latex. This poses a risk of allergic reactions in latex-sensitive individuals and must be considered during patient screening.[1]

VI. Efficacy and Immunogenicity Data

A. The Principle of Inferred Efficacy

The assessment of efficacy for diphtheria and tetanus vaccines is unique among modern biologicals. According to authoritative sources, including the U.S. Centers for Disease Control and Prevention (CDC), the clinical efficacy of tetanus and diphtheria toxoids has never been studied in a modern, randomized, placebo-controlled vaccine trial.[18] Such trials were not conducted before the vaccines became standard of care, and it would be profoundly unethical to conduct them now, given the severity of the diseases and the vaccines' established record of success.

Consequently, vaccine effectiveness is not measured directly but is inferred from immunogenicity data. The surrogate marker for protection is the level of specific antitoxin antibodies in the recipient's serum. A serum antitoxin level of ≥0.01 International Units per milliliter (IU/mL) is widely accepted as the minimum level required to confer protection against both tetanus and diphtheria.[10] This serological correlate of protection is the foundational principle upon which the entire regulatory and clinical framework for these vaccines is built.

B. Immunogenicity and Clinical Effectiveness

Based on decades of epidemiological data and immunogenicity studies, the effectiveness of a complete vaccination series is exceptionally high.

• Clinical Efficacy: A complete primary vaccination series is estimated to have a clinical efficacy of virtually 100% for tetanus and 97% for diphtheria.[18]
• Immunogenicity of ADT™ Booster: While specific clinical trial data for ADT™ Booster is not detailed in the provided materials, the product information confirms that it stimulates the immune system to form protective antibodies.[1] The consumer medicine information leaflet states that most recipients of the booster dose will produce sufficient antibodies to protect against both diseases.[6]
• Supporting Data from Similar Vaccines: Data from a comparable Td vaccine, TDVAX, provides strong supporting evidence for the expected immunogenicity. In clinical studies of TDVAX, a three-dose primary series resulted in 100% of adult subjects achieving protective antitoxin levels for both tetanus and diphtheria. Furthermore, booster doses administered to previously immunized individuals reliably induced protective antibody levels in all subjects.[16] This demonstrates the robust and predictable immune response elicited by adsorbed Td toxoid vaccines.

C. The Scientific Debate on Booster Interval and Duration of Immunity

A significant point of discussion in modern vaccinology is the optimal interval for adult Td booster doses.

• Conventional Recommendation: The traditional recommendation, reflected in the ADT™ Booster product information, is for a booster dose every 10 years, with protection expected to last "up to 10 years".[1] This decennial schedule is endorsed by public health bodies such as the U.S. Advisory Committee on Immunization Practices (ACIP).[22]
• Emerging Evidence for Longer Immunity: This long-standing convention is being challenged by compelling recent research.
• A 2016 study led by Dr. Mark Slifka at Oregon Health & Science University analyzed immunity in 546 adults and concluded that after a standard five-dose childhood vaccination series, protective antibody levels against tetanus and diphtheria are maintained for at least 30 years.[23] Based on these findings, the researchers proposed that the adult booster schedule could be revised to require vaccinations only at age 30 and again at age 60.
• A subsequent, larger-scale epidemiological study by the same research group, published in 2020, compared tetanus and diphtheria disease rates across 31 North American and European countries between 2001 and 2016. The study found no significant difference in disease incidence between countries that mandate 10-year adult boosters and those that do not.[24] This real-world evidence strongly suggests that the primary childhood vaccination series may be sufficient to provide lifetime protection.
• Policy and Economic Implications: The discrepancy between established policy and this emerging scientific evidence has significant implications. Adopting a longer, evidence-based booster interval could simplify adult vaccination schedules and lead to substantial cost savings for healthcare systems. The researchers estimated that changing from a 10-year to a 30-year schedule in the U.S. alone could save approximately $1 billion annually in unnecessary medical costs.[24] This ongoing debate highlights a critical tension between established public health practice and evolving scientific understanding.

VII. Global Regulatory Status and Market Landscape

A. Regulatory Approval and Status of ADT™ Booster

The market presence of ADT™ Booster is highly regional, primarily confined to Australia and New Zealand.

• Australia: ADT™ Booster received marketing authorization from the Therapeutic Goods Administration (TGA) on December 11, 2006, and is identified by ARTG ID 130919.[4] It is an established part of the national immunization strategy, being listed on the Pharmaceutical Benefits Scheme (PBS) for subsidized access [2] and included as a registered dT booster option in the Australian Immunisation Handbook for individuals aged 5 years and older.[15]
• United States: ADT™ Booster is not licensed for use in the United States. A comprehensive review of vaccines approved by the U.S. Food and Drug Administration (FDA) and listed by the CDC confirms that only two Td vaccines are available in the U.S. market: TENIVAC® (sponsored by Sanofi Pasteur) and TDVAX® (manufactured by MassBiologics).[25] The U.S. product portfolio of Seqirus is exclusively focused on influenza vaccines, with no diphtheria or tetanus products listed.[28]
• Europe: Similarly, ADT™ Booster does not appear to be authorized for use within the European Union. It is not found on lists of nationally authorized medicines compiled by the European Medicines Agency (EMA).[30] While various diphtheria-tetanus combination vaccines are available in Europe, the specific Seqirus product is not among them.[31]

B. Comparative Analysis of Td Vaccines in Key Markets

A comparison of ADT™ Booster with its U.S. counterparts reveals subtle but important differences in formulation and sponsorship, underscoring the fragmented nature of the global Td vaccine market.

Table 3: Comparative Overview of Td Vaccines (Australia vs. US)

Attribute	ADT™ Booster (Seqirus)	TENIVAC® (Sanofi Pasteur)	TDVAX® (MassBiologics)
Sponsor/Manufacturer	Sponsor: Seqirus Pty Ltd Manufacturer: AJ Vaccines A/S	Sanofi Pasteur Limited	MassBiologics
Primary Market	Australia, New Zealand	United States	United States
Age Indication	≥5 years	≥7 years	≥7 years
Diphtheria Toxoid Content	≥2 IU	2 Lf (Limes of flocculation unit)	2 Lf
Tetanus Toxoid Content	≥20 IU	5 Lf	2 Lf
Adjuvant	Aluminium hydroxide	Aluminium phosphate	Aluminium phosphate
Preservative	None	None	Trace thimerosal (not as preservative)
Latex in Packaging	Yes (syringe tip cap)	Yes (syringe tip cap)	Not specified in snippets

Sources: ADT Booster [1]; TENIVAC® [18]; TDVAX® [16]

C. Manufacturer Profile: CSL Seqirus's Strategic Position

The context of ADT™ Booster within the broader CSL Seqirus portfolio is revealing. CSL Seqirus presents itself globally as one of the world's largest influenza vaccine companies, with a strategic focus on influenza prevention and pandemic preparedness.[5] The company's innovation and manufacturing prowess are centered on its egg-based, cell-based, and adjuvanted influenza vaccine platforms, produced at its state-of-the-art facilities in the US, UK, and Australia.[7]

However, CSL Seqirus's identity in Australia is also shaped by the legacy of its parent company, CSL, which was founded in 1916 to serve Australia's public health needs.[5] CSL Seqirus continues this unique public health role as the manufacturer and sole supplier of a range of products made for the Australian Government "in the National Interest." This portfolio includes critical products such as snake and spider antivenoms, Q fever vaccine, and, by extension, ADT Booster.[7]

This analysis leads to the conclusion that ADT™ Booster is a "regional legacy" product. Its continued availability is not driven by a global commercial strategy but by a long-standing contractual obligation to the Australian public health system. This is strongly supported by the fact that the vaccine appears only on Seqirus's Australian website [3] and is absent from its global and U.S. product listings, which are dominated by influenza vaccines.[28]

This situation also sheds light on the global supply chain for older, essential vaccines. The Td vaccine market in the U.S. has proven to be fragile, recently facing a potential shortage when MassBiologics, one of only two suppliers, temporarily ceased production of TDVAX.[39] The fact that a major global vaccine player like Seqirus sources its Australian Td vaccine from a third-party Danish manufacturer [1] rather than producing it within its own extensive network highlights a fragmented and potentially vulnerable global supply chain for these lower-margin, yet medically essential, products.

VIII. Expert Analysis and Concluding Remarks

ADT™ Booster represents a cornerstone of public health: a safe, reliable, and effective vaccine against two severe, toxin-mediated diseases. Its formulation as a reduced-antigen-content booster is immunologically sound, and its safety profile is well-understood after decades of use of similar Td vaccines worldwide. The vaccine's approval and subsidization in Australia underscore its integral role in the nation's immunization program, reflecting a successful, long-term public health partnership between the Australian government and CSL/Seqirus.

While the product itself is a standard and unremarkable example of a Td vaccine, its context reveals several critical points. First, it exemplifies how a global pharmaceutical leader like Seqirus can maintain a dual identity, balancing a commercially driven, innovation-focused global strategy in influenza with a regional, public-health-oriented role in its home country by providing essential legacy products. Second, the reliance on an external manufacturer and the fragility seen in the U.S. Td market suggest that the global supply chain for older, less profitable vaccines may warrant closer scrutiny by public health agencies to ensure long-term stability.

The most significant and actionable conclusion drawn from this comprehensive analysis relates to the recommended booster interval. The current practice of administering ADT™ Booster based on a conventional 10-year schedule is not fully aligned with a compelling and growing body of high-quality scientific evidence. Immunological and epidemiological studies strongly suggest that immunity conferred by a complete childhood primary vaccination series persists for at least 30 years, and perhaps for life.

Therefore, it is the expert recommendation of this report that public health authorities, particularly Australia's TGA and the expert committees that inform the Australian Immunisation Handbook, should undertake a formal and comprehensive review of the latest evidence on the duration of immunity for tetanus and diphtheria. Such a review should critically assess the necessity of the decennial booster schedule for the general adult population. A potential shift to a longer interval (e.g., a 30-year schedule) would not only align national policy with the best available scientific evidence but could also simplify the adult vaccination schedule, improve compliance, and generate significant cost savings for the healthcare system without compromising public health protection. ADT™ Booster, as a trusted public health tool, can continue its vital role, but its use should be optimized according to the most current scientific understanding of long-term immunity.

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