How Zoster Vaccine Recombinant Adjuvanted (Shingrix) Works: Recombinant VZV glycoprotein E (gE) subunit antigen with AS01B adjuvant to drive protective immune responses.
Last updated:
March 2026
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Quick Summary
Zoster Vaccine Recombinant, Adjuvanted (Shingrix) is a recombinant glycoprotein E (gE) subunit vaccine formulated with the AS01B adjuvant system. It is indicated for prevention of herpes zoster (shingles) in adults at increased risk due to immunodeficiency or immunosuppression. The recombinant gE antigen plus AS01B adjuvant are designed to generate protective immunity against VZV.
Properties
Details
Generic Name
Zoster Vaccine Recombinant, Adjuvanted
Brand Names
Shingrix
Drug Class
Vaccine
Primary Target
Varicella-zoster virus glycoprotein E (gE) antigen (VZV gE)
Approved Indications
Prevention of herpes zoster (shingles) and postherpetic neuralgia (PHN) in adults ≥50 years, prevention of herpes zoster and PHN in adults ≥18 years at increased risk due to immunodeficiency or immunosuppression
Development History
Zoster vaccine recombinant, adjuvanted (RZV; brand name Shingrix) was developed by GlaxoSmithKline Biologicals as a recombinant subunit vaccine formulated to restore varicella-zoster virus (VZV)-specific cellular and humoral immunity in adults whose VZV-specific T-cell responses decline with age. The active antigen is recombinant VZV glycoprotein E (gE), the most abundant surface protein on VZV virions, produced in a baculovirus-insect-cell expression system and combined with the AS01B Adjuvant System — a liposome-based formulation containing MPL and QS-21. The design choice of AS01B over lower-dose or alternative adjuvant systems was intentional: preclinical comparisons demonstrated that gE/AS01B elicited CD4+ T-cell responses 5.4-fold greater than gE/AS03 in VZV-primed mice, directly addressing the failure mode of the licensed live-attenuated competitor (Zostavax), which provided only ~51% efficacy that waned sharply with age and was contraindicated in immunocompromised patients. RZV was engineered as a non-replicating, non-live vaccine precisely to enable use in populations where a live vaccine could not safely be administered.
The pivotal approval program comprised two concurrent randomized, placebo-controlled Phase III trials. ZOE-50 (NCT01165177) enrolled 15,411 adults aged ≥50 years across 18 countries, with the primary endpoint of herpes zoster incidence; ZOE-70 (NCT01165229) enrolled 13,900 adults aged ≥70 years at the same sites. In ZOE-50, overall vaccine efficacy against herpes zoster was 97.2% (95% CI 93.7–99.0) across all age groups, with consistent protection from the 50–59 through ≥70 cohorts. In ZOE-70, efficacy was 89.8% (95% CI 84.2–93.7) in the individual trial and 91.3% in a prespecified pooled analysis with ZOE-50 for adults ≥70; efficacy against postherpetic neuralgia reached 88.8% in that pooled population. The FDA approved RZV on October 20, 2017, for prevention of herpes zoster in immunocompetent adults aged ≥50 years under the brand name Shingrix; RZV simultaneously displaced the live-attenuated vaccine as the preferred shingles vaccine in ACIP recommendations.
RZV's label has since expanded in two meaningful steps. First, the immunocompromised indication: supported by the ZOSTER-006 (autologous hematopoietic stem-cell transplant recipients), ZOSTER-028 (allogeneic HSCT), ZOSTER-039 (solid tumor patients on chemotherapy), and related trials in HIV and renal transplant populations, the FDA expanded RZV's indication on July 23, 2021, to include adults aged ≥18 years who are or will be at increased risk for herpes zoster due to immunodeficiency or immunosuppression caused by known disease or therapy — making RZV the first herpes zoster vaccine approved for immunocompromised persons. A meta-analysis of seven RCTs in immunocompromised populations found RZV reduced herpes zoster incidence by 81% versus placebo. Second, the ACIP codified ACIP recommendations for this expanded group in October 2021, applying to adults ≥19 years. The current label in the United States thus covers two broad populations: immunocompetent adults ≥50 years and immunocompromised adults ≥18 years, with a two-dose intramuscular schedule (0 and 2 months) under the single brand name Shingrix.
Detailed Mechanism of Action
Antigen composition and gE biology. Shingrix delivers a single recombinant antigen — varicella-zoster virus (VZV) envelope glycoprotein E (gE), the most abundantly expressed glycoprotein on the viral envelope, formulated with the AS01B liposome adjuvant system. GE is an essential type I membrane glycoprotein: in the native virion it forms a non-covalent heterodimer with glycoprotein I (gI) that is required for efficient cell-to-cell viral spread and secondary envelopment during productive infection. Outside its structural role, gE mediates host-cell engagement through binding to insulin-degrading enzyme (IDE) via a defined N-terminal domain; amino-acid deletions in this region reduce cell-to-cell spread and skin infection in vivo, reinforcing gE's centrality to the viral life cycle. Because gE sits at the intersection of envelope assembly, cell-to-cell transmission, and antibody recognition, selecting it as the sole vaccine antigen is sufficient to recapitulate the principal antigenic targets of protective anti-VZV immunity.
AS01B adjuvant formulation and tissue distribution. AS01B is a liposome-based system co-formulating two immunostimulants — monophosphoryl lipid A (MPL) and the saponin QS-21 — together with cholesterol and the phospholipid DOPC. After intramuscular injection the formulation does not form a prolonged depot: QS-21 and co-delivered antigen are detectable in the muscle interstitium within 30 minutes but are almost undetectable by 24 hours, consistent with a transient innate-activation burst rather than sustained antigen persistence. This rapid clearance confines the initial inflammatory signal to the injection site and draining lymph node (dLN), limiting systemic exposure while establishing the local context for adaptive priming.
MPL–TLR4 innate signaling. MPL (3-O-desacyl-4′-monophosphoryl lipid A) directly engages Toll-like receptor 4 (TLR4) on antigen-presenting cells (APCs). TLR4-dependent signaling is functionally required for AS01's adjuvant activity: TLR4 ligation activates NF-κB–linked transcriptional programs that drive cytokine production and upregulate T-cell co-stimulatory molecules, including CD86 and CD40 on dendritic cells (DCs) and monocytes recruited to the dLN. Concurrently, neutrophils and monocytes transiently accumulate at the injection site, returning to baseline by day 7.
QS-21 inflammasome activation and antigen cross-presentation. In parallel, QS-21 undergoes cholesterol-dependent endocytosis, destabilizing lysosomal membranes and facilitating escape of antigen to the cytosol, where it gains access to MHC-I processing pathways and can prime CD8⁺ T cells. QS-21 simultaneously acts as a direct inflammasome activator: it triggers the NLRP3 inflammasome, driving caspase-1–dependent maturation of IL-1β and IL-18 — detectable in the dLN within one hour of injection. The adjuvant effect of QS-21 depends on integration of caspase-1 and MyD88 pathways and local HMGB1 release, coupling inflammasome activity to additional innate signaling nodes.
Innate-to-adaptive bridging and Th1 polarization. The synergistic MPL + QS-21 program generates an early IFN-γ response in the dLN within hours of vaccination. This innate IFN-γ is produced by NK cells and CD8⁺ T cells and is controlled by subcapsular sinus macrophage–derived IL-18, acting in concert with IL-12, linking QS-21-dependent IL-18 maturation to the IFN-γ–dominated conditioning environment. Ex vivo antigen-presentation assays establish that activated DCs isolated from the dLN of vaccinated mice are the proximal cellular drivers of CD4⁺ T-cell priming; depletion of those DCs completely abrogates the adjuvant-enhanced antigen-specific response.
Adaptive immunity and clinical translation. The IFN-γ–skewed innate environment steers gE-specific helper T cells toward a polyfunctional Th1 phenotype simultaneously expressing IFN-γ, IL-2, and TNF-α; combining MPL with QS-21 is required to reach the highest magnitude and polyfunctionality of this response. Coordinated gE-specific antibody responses develop alongside cellular immunity, with IgG subclass profiles shaped in part by IFN-γ receptor signaling. These durable, polyfunctional gE-specific CD4⁺ T cells and antibodies maintain immunological surveillance over VZV latently infected in sensory ganglia, restricting viral reactivation. In the ZOE-50 phase 3 trial, this mechanism translated to 97.2% efficacy against herpes zoster in adults aged 50 and older; the ZOE-70 trial confirmed high and consistent protection in adults aged 70 and above, regardless of age at vaccination. The superiority of this adjuvanted subunit approach over the live-attenuated zoster vaccine is attributed to higher and more durable gE-specific memory Th1-type responses.
Clinical Relevance
Approved Indications
Prevention of Herpes Zoster in Adults ≥50 Years: The AS01B-adjuvanted recombinant glycoprotein E vaccine demonstrated 97.2% efficacy against herpes zoster in adults ≥50 (ZOE-50) and 89.8% efficacy in adults ≥70 (ZOE-70), with durable protection through at least 4 years.
Prevention in Immunocompromised Adults ≥18 Years: FDA-approved for adults who are or will be at increased risk of herpes zoster due to immunodeficiency or immunosuppression caused by known disease or therapy, based on immunogenicity and safety data across multiple immunocompromised populations.
Key Drug Interactions (Mechanism-Based)
Immunosuppressive Therapies: Corticosteroids, calcineurin inhibitors, and antimetabolites may reduce vaccine-induced immune responses; ACIP recommends vaccinating before initiating immunosuppression when feasible.
Anti-CD20 Monoclonal Antibodies: Rituximab-mediated B-cell depletion may blunt anti-gE antibody seroconversion while preserving T-cell responses; delay vaccination until B-cell reconstitution when possible.
Concomitant Vaccination: Coadministration with inactivated influenza vaccine showed no interference in immune response to either vaccine; however, concomitant PPV23 was associated with increased fever (16% vs 7%) and shivering (21% vs 7%) compared with RZV alone.
Emerging Indications
Oncology
Solid Tumors Undergoing Chemotherapy (Phase 3): Chemotherapy-induced immunosuppression markedly elevates VZV reactivation risk, and RZV's non-live AS01B-adjuvanted platform allows vaccination in patients who cannot receive live vaccines. A phase 3 randomized trial (NCT01798056) in solid tumor patients vaccinated before or during chemotherapy found that RZV was immunogenic in both timing cohorts, with immune responses persisting at 12 months; full efficacy data were published in Cancer (2019) and showed a favorable safety profile with no increase in serious adverse events versus placebo.
Hematologic Malignancies on Immunosuppressive Cancer Therapy (Phase 3): Patients with hematologic malignancies face HZ incidence up to 25-fold above the general population due to disease- and treatment-related immunosuppression. A phase 3 observer-blind trial (NCT01767467) randomized adults ≥18 years with leukemia, lymphoma, or myeloma on immunosuppressive cancer therapy to RZV or placebo, meeting both co-primary immunogenicity endpoints at 1 month post-dose 2, though responses were attenuated in non-Hodgkin B-cell lymphoma and CLL subgroups, as reported in Open Forum Infectious Diseases (2017).
Chronic Lymphocytic Leukemia (Phase 2): CLL-associated immune dysregulation impairs humoral vaccine responses, raising questions about whether RZV's cell-mediated immunity arm can compensate. A phase 2 open-label study (NCT03702231) in treatment-naïve and BTK-inhibitor–treated CLL patients found RZV to be well-tolerated with grade 1–2 adverse events predominating and early evidence of humoral responses, with preliminary results presented at ASH 2019.
Immunology
Autoimmune Rheumatic Diseases (Phase 4): Patients with rheumatoid arthritis, SLE, inflammatory myopathies, and related ARDs face elevated HZ risk from both the underlying immune dysregulation and immunosuppressive therapies, yet prospective RCT data in this population remained limited. A double-blind, randomized, placebo-controlled phase 4 study of 1,180 ARD patients and 393 healthy controls (NCT04425018) is evaluating disease activity safety, humoral and cellular immunogenicity, and incident HZ; interim immunogenicity and safety results were published in Journal of Clinical Rheumatology (2025).
Autoimmune Diseases — Real-World Effectiveness (Phase 4/RWE): Real-world effectiveness data complement trial immunogenicity endpoints for autoimmune populations on diverse therapies. A retrospective matched cohort using Optum Clinformatics data (2018–2021) across 145,874 patients with rheumatoid arthritis, IBD, SLE, MS, psoriasis, and psoriatic arthritis found an overall two-dose RZV vaccine effectiveness of 66.3% against HZ, ranging from 48.1% in multiple sclerosis to 77.2% in psoriasis, as reported in Journal of Infectious Diseases (2025).
Nephrology
Renal Transplant Recipients — Adults ≥18 Years (Phase 3): Chronic immunosuppression in renal transplant recipients increases HZ incidence 8–9-fold versus the general population, and the non-live vaccine platform removes the contraindication that applies to live-attenuated zoster vaccine. A phase 3 randomized, observer-blind multicenter trial (NCT02058589) in 264 renal transplant recipients on stable immunosuppressive therapy found that two RZV doses induced persistent gE-specific humoral and cell-mediated immune responses through 12 months post-dose 2 without increasing rejection rates, allograft dysfunction, or serious adverse events, as published in Clinical Infectious Diseases (2019).
Young Adult Solid Organ Transplant Recipients 19–40 Years (Phase 2): ACIP expanded RZV recommendations to immunocompromised adults ≥19 years in 2021, but detailed immunologic and safety data in young transplant recipients are sparse. An ongoing safety and immunogenicity study in heart, liver, and kidney transplant recipients aged 19–40 years found RZV to be generally well-tolerated across 23 participants receiving dose 1, with one serious adverse event (transient right ventricular dysfunction post-dose 2) not attributable to rejection, as reported at OFID 2026.
Oncology / Hematology — Allogeneic Transplant
Allogeneic Hematopoietic Cell Transplant Recipients (Observational / Phase 2 planning): AlloHCT recipients face the highest HZ risk among transplant populations due to prolonged immune reconstitution and GVHD, yet RZV efficacy data in this setting are absent compared to the autologous setting. A prospective observational single-center cohort at Princess Margaret Hospital (n=445 alloHCT recipients, 2018–2024) found that two doses of aRZV did not significantly reduce HZ frequency overall (relative risk 0.90 versus unvaccinated), though severity was modified and vaccinees had no cases of disseminated HZ, with findings published in Transplantation and Cellular Therapy (2025) and calling for a prospective RCT.
Clinical Trials of Zoster Vaccine Recombinant Adjuvanted
Phase Design
N Enrolled
Intervention
Indication
Primary Endpoint
Key Result
Status
Trial data synthesized by Elicit's AI research agent from peer-reviewed publications and ClinicalTrials.gov filings.
Zoster Vaccine Recombinant Adjuvanted Competitive Landscape
This table shows how Zoster Vaccine Recombinant, Adjuvanted (Shingrix) compares to other vaccines and options for herpes zoster prevention. Each entry breaks down the representative vaccines and drugs, their targets, and how they work in the body.
Drug Class
Representative Drug(s)
Primary Molecular Target
Mechanism of Action
Key Efficacy Outcomes
Route & Dosing
Safety / Risk Profile
Key Limitations
Competitive landscape synthesized by Elicit's AI research agent from peer-reviewed pharmacology literature and regulatory filings.
Open Research Questions
What is the minimum correlate of protection for recombinant zoster vaccine, and can it be used to guide booster timing?
Defining a validated immunological threshold would transform post-vaccination monitoring and help clinicians decide when re-dosing is warranted, particularly in the very elderly. Despite robust immunogenicity data, no well-defined correlate of protection has been established; a 2024 systematic meta-analysis across 37 studies found immune waning accelerates in the very elderly, underscoring the need for further research on long-term immunity, and a 2023 JCI study showed that pre-vaccination naive CD4+ T cell frequency predicts persistence of gE-specific clonotypes at five years, but translation into a clinical decision rule remains unresolved.
How does immunosuppressive therapy type and timing modulate RZV immunogenicity, and can personalized vaccination schedules improve responses in poor responders?
Immunocompromised individuals carry the highest HZ burden yet show the most variable vaccine responses, making schedule optimization clinically urgent. A 2024 PLoS ONE meta-analysis of seven RCTs found that transplant recipients and patients with past malignancy were associated with lower immunogenicity, while a 2025 literature review identified Rituximab and post-transplant immunosuppression as drivers of reduced responsiveness and called for biomarker-guided, personalized vaccination schedules as a research priority.
To what extent does the real-world effectiveness gap between RZV trial efficacy (~97%) and observed effectiveness (~76-87%) reflect methodological artefact versus true population-level attenuation?
Understanding this gap matters for policy modelling and for identifying subpopulations where protection is genuinely lower. A large Vaccine Safety Datalink cohort of nearly two million adults reported two-dose effectiveness of 76%, substantially below the pivotal trial figure, while a Kaiser Permanente study found effectiveness of 74% against herpes zoster with stable protection over four years but lower single-dose coverage against postherpetic neuralgia; whether residual confounding, diagnostic coding errors, or genuine immunological factors explain the discrepancy is actively debated.
What is the mechanism by which AS01B adjuvant elicits high vaccine efficacy even in octogenarians, and how does innate immune priming translate into durable adaptive responses?
Resolving this question could inform rational adjuvant design for other age-related infectious diseases. A 2024 Expert Review study confirmed AS01 induces a rapid innate gene signature predictive of adaptive response magnitude, but noted that efforts to fully define AS01 mechanisms across different vaccine settings are ongoing; separately, a 2024 study in monocyte co-cultures showed AS01 strongly activates classical and non-classical monocytes via TNF-α and IL-1R pathways, but how this cascade connects to long-term T cell memory generation in older adults remains incompletely understood.
Does RZV generate clinically meaningful trained immunity, and could this heterologous protection contribute to non-specific benefits beyond herpes zoster prevention?
If AS01B-adjuvanted vaccination broadly reshapes innate immune memory, it would have substantial implications for vaccination strategy in ageing and immunocompromised populations. A 2024 study in RZV recipients found persistent innate immune responses to both gE and unrelated antigens (including CMV) for up to five years, with chromatin remodelling at the TGF-β locus, suggesting RZV generates robust homologous and heterologous trained immunity; however, whether this translates into measurable clinical protection against non-VZV infections in prospective trials has not yet been established.
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This mechanism of action page was generated using Elicit's AI research agent, which synthesizes explanations from peer-reviewed pharmacology literature. Every pathway description and citation is traceable — because in pharmacology, accuracy isn't optional.
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