This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Study to Evaluate Immunogenicity and Safety of GSK Biologicals' Herpes Zoster Subunit (HZ/su) Vaccine at 9 and 10 Years After Vaccine Administration and Assessment of Re-vaccination With 2 Additional Doses at 10 Years After Initial Vaccination, in Healthy Subjects Aged 60 Years of Age(YOA) and Older (NCT02735915), a na phase 3 study. The primary outcome is Anti-glycoprotein (gE) Specific Antibody (Ab) Concentrations.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02735915 |
| Phase | Phase 3 |
| Condition | Herpes Zoster |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 70 |
| Arms in the primary outcome | n/a |
| Lead sponsor | GlaxoSmithKline |
| Results posted | Yes |
2. Clinical Question
Population
The study enrolled healthy subjects aged 60 years and older who had completed the 2-dose HZ/su vaccination course in the earlier Zoster-003 study. The registry reports enrollment of 70. The primary persistence analysis was defined for an according-to-protocol immunogenicity cohort, not necessarily every enrolled subject; its size is not reported in the registry record.
Intervention
The study evaluated the GSK1437173A herpes zoster vaccine. Its aims included assessing immune response persistence after the earlier vaccination course and evaluating responses after revaccination with 2 additional doses at 10 years after the first dose of that course. The arm description says that 62 subjects received 1 or 2 additional doses during the revaccination phase.
Comparator
There was no concurrent control group. The study is classified as single-group, with allocation listed as not applicable and no masking. The findings therefore describe measurements in the enrolled group; they do not constitute a randomized, like-for-like comparison between vaccinated and unvaccinated participants or between alternative vaccination strategies.
Primary question
At month 108 after the first dose of the initial vaccination course, what was the geometric mean concentration of antibodies specific to glycoprotein E, measured by ELISA? The endpoint addresses persistence of an immune marker at that time point. The registry record names a 95% confidence interval as its dispersion measure, but does not report the GMC estimate or its interval.
3. Trial Design
This completed phase 3 study was a single-group, unmasked follow-up study of people who had previously completed a 2-dose herpes zoster subunit vaccine course in Zoster-003. The registry describes the participants as healthy subjects aged 60 years and older. Enrollment was 70. The study was not a randomized comparison: allocation is listed as not applicable, and no concurrent control arm is described.
The stated purpose was to evaluate persistence of immune response and safety up to 10 years after the first dose of the initial course. It also assessed immune responses following revaccination with 2 additional doses at 10 years after that first dose. In the revaccination phase, 62 subjects received 1 or 2 additional doses. The registry does not explain why some received 1 dose and others 2, or provide a comparison between those subgroups.
The primary outcome was anti-gE antibody concentration at month 108 after the first dose of the initial course. Listed secondary outcomes cover antibody concentrations and antigen-specific CD4 T-cell frequencies, including measures after revaccination, as well as adverse events. The registry record lists 14 outcome measures and zero analyses. It does not report a concurrent comparator, randomization, masking, or a statistical analysis plan. The study dates are 2016-04-11 to 2017-08-28, and its status is completed.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Before assignment: Out of 70 subjects originally enrolled (Total enrolled cohort for persistence phase) into the study, 8 subjects were eliminated as subject number was allocated without vaccine administration. Only 62 subjects were vaccinated with at least one dose, forming the Total vaccinated cohort(TVc) for re-vaccination phase.
Overall Study
| Stage | GSK1437173A Vaccine Group |
|---|---|
| STARTED | 70 |
| Vaccinated | 62 |
| COMPLETED | 59 |
| NOT COMPLETED | 11 |
Reasons for not completing this period:
| Reason | GSK1437173A Vaccine Group |
|---|---|
| Not vaccinated but subject ID assigned | 8 |
| Withdrawal following SAE | 2 |
| Withdrawal by Subject | 1 |
Analysis population for the primary outcome, as defined in the registry: The analysis for persistence at month 108 was performed on the According-to-protocol (ATP) cohort analysis of immunogenicity at Year 9, which included subjects who complied with the protocol criteria and had immunogenicity results available up to the timepoint considered.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | GSK1437173A Vaccine Group |
|---|---|---|
| Participants analysed | 70 | |
| Age, Continuous | Years | 72.3 (SD 4.3) |
| Sex: Female, Male: Female | Participants | 43 |
| Sex: Female, Male: Male | Participants | 27 |
| Race/Ethnicity, Customized: White-Caucasian/European Heritage | Participants | 70 |
6. Primary Endpoint
The registry lists the primary outcome as Anti-glycoprotein (gE) Specific Antibody (Ab) Concentrations, measured over At Month 108 post first dose of initial vaccination course in study Zoster-003 (NCT00434577)..
| Element | Registry entry |
|---|---|
| Result type | Geometric Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | mIU/mL |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the concentration of antibodies specific to glycoprotein E (gE), a vaccine-related immune marker. The registry says that concentrations were measured using an enzyme-linked immunosorbent assay (ELISA), expressed in mIU/mL, and summarized as a geometric mean concentration (GMC). The measurement was scheduled at month 108 after the first dose of the original vaccination course.
A GMC summarizes concentration data on a multiplicative scale. In general, this can be useful when measurements vary over a wide range or have a skewed distribution: analysis on a logarithmic scale can make the summary less dominated by unusually high values. That is a general statistical rationale, not a reported claim about the distribution in this study. The registry does not provide assay performance details or the observed concentration distribution.
The endpoint is used to describe persistence of an antibody response at a specified follow-up time. It is an immune measurement, not a direct count of clinical herpes zoster cases. The registry names a 95% confidence interval as the measure of dispersion, but neither the GMC nor its interval is reported in the registry record. The size of the according-to-protocol cohort used for this endpoint is also not reported.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a study designed to measure long-term anti-gE antibody concentrations after an earlier vaccination course and to evaluate immune responses and safety following later revaccination. Its primary endpoint is a GMC at month 108 after the first dose of the initial course, with a 95% confidence interval specified as the uncertainty measure. However, the posted registry record does not give the GMC, its interval, or an analysis result. It is therefore not possible to characterize the observed antibody level or its precision from this record.
The same distinction applies to the stated secondary immune outcomes. The registry lists antibody concentrations and antigen-specific CD4 T-cell frequencies, including post-revaccination measures, but does not provide their estimates. It also lists safety outcomes, and the adverse-event record gives counts for serious and other adverse events. Those counts describe events in this group; without a concurrent control group, they cannot establish how event frequency compares with an alternative intervention or with no vaccination.
The study is single-group and unmasked, with allocation not applicable. It follows people who had previously completed the earlier vaccine course, so the participants are a selected cohort with that prior history rather than a newly assembled comparison population. The reported primary analysis population was the according-to-protocol immunogenicity cohort at Year 9. The record does not report how many participants met those criteria or how that cohort differed from the enrolled group.
The safety record identifies 62 participants at risk for the listed event counts, with 7 affected by serious adverse events, 53 affected by other adverse events, and 0 deaths. The serious-event terms listed in the record each have a reported frequency of 1.6%. These entries do not by themselves show event timing, duration, severity beyond the serious classification, or whether events were considered related to the study intervention. The registry lists an outcome concerning related serious adverse events, but the group counts are not enough to resolve that detail.
Overall, the registry supports a description of study aims, design, endpoint definitions, and selected safety counts. It does not support a conclusion about the magnitude or precision of the primary immune response, a difference between vaccination strategies, or a causal safety comparison. Such results are not reported in the registry record.
9. Statistical Methods Explained
What does a geometric mean summarize?
A geometric mean is a summary for positive measurements formed by working with their logarithms, averaging on that scale, and transforming the average back to the original measurement scale. In general, this approach is often used for concentration data because such measurements can be right-skewed: a small number of high values may pull an ordinary arithmetic average upward. The GMC is interpreted as a central concentration on a multiplicative scale, rather than as the ordinary average concentration.
That general explanation does not establish the distribution of anti-gE measurements in this study. The registry specifies the GMC as the primary summary but does not report raw measurements, distributional checks, transformations, or analysis code. Nor does it provide a numeric GMC that can be interpreted alongside the assay units.
What does the confidence interval express?
A confidence interval describes the statistical uncertainty around an estimate under the assumptions of the method used to calculate it. In general, a narrower interval indicates greater precision, while a wider interval indicates less precision. The interval does not indicate the range containing every participant’s measurement, and it is not a guarantee that a particular value is the true population value.
The registry specifies a 95% confidence interval for the primary GMC. It does not report the interval endpoints, the method used to construct the interval, or the number of participants included in that primary analysis. Consequently, the precision of the primary estimate cannot be assessed from the registry record.
Why does the analysis population matter?
The primary persistence analysis is described as using the according-to-protocol immunogenicity cohort at Year 9. The registry defines this cohort in terms of protocol compliance and immunogenicity results available through the time point considered. In general, an according-to-protocol analysis focuses on participants meeting specified study requirements and with the measurements needed for the analysis. It can differ from an analysis of everyone enrolled or everyone who began follow-up.
The registry does not give the cohort size, the number excluded, the reasons for exclusion, or a comparison of included and excluded participants. Without these details, it is difficult to judge how much the analysis population may differ from the full enrolled group, or whether missing measurements could have affected the estimate.
What does a single-group design permit?
In a single-group study, outcomes are observed in one group rather than compared under randomized assignment with a concurrent control. Repeated immune measurements can describe how marker levels appear at specified times, and safety events can be counted among participants followed. In general, however, changes over time or observed event counts cannot isolate the effect of vaccination from other influences without an appropriate comparison design and analysis.
This study followed people who had already completed the original vaccine course. The revaccination phase included participants who received 1 or 2 additional doses, but the record does not report a randomized comparison of those dose histories. It also does not state an adjustment strategy or a statistical model for comparing subgroups. No such comparison should be inferred from the design description alone.
What can be inferred from the registry analysis fields?
The registry lists 14 outcome measures and zero analyses. That means the record includes outcome descriptions but no posted analysis results in its analysis listings. Outcome definitions are not results: naming an antibody concentration, T-cell frequency, or adverse-event measure does not reveal its observed value, uncertainty, or statistical significance.
In general, immune concentration data may be analyzed on a logarithmic scale, and repeated measurements may require methods that account for within-person dependence. These are general methodological possibilities, not methods confirmed for this study. The registry does not report the statistical tests, model specification, covariate adjustment, handling of repeated measurements, or method for missing observations. No inferential result should be reconstructed without those details and the underlying estimates.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 14 outcome measures, including antibody concentrations, antigen-specific CD4 T-cell frequencies, and safety outcomes. When a study evaluates multiple outcomes or time points, general statistical practice recognizes a multiplicity issue: conducting many tests can increase the chance of at least one apparently unusual result. A prespecified hierarchy, adjustment method, or clear distinction between primary and exploratory analyses can help readers interpret such testing. The registry identifies a primary endpoint, but a multiplicity strategy is not reported in the registry record.
The record does not report interim analyses, stopping rules, or a detailed statistical analysis plan. It also does not specify how missing immune measurements were handled, whether missingness was examined by reason, or whether sensitivity analyses were planned. These details matter because the primary population required both protocol compliance and immunogenicity results available at the time point considered. The number of participants with unavailable results and the reasons are not reported.
The record describes enrollment of 70 and an according-to-protocol cohort for the primary persistence analysis, but the analysis cohort size is not stated. The 62 participants described as receiving 1 or 2 additional doses during revaccination should not be treated as the denominator for every immune outcome without outcome-specific counts. Those denominators are not reported. These omissions limit evaluation of missing-data risk, selective availability of measurements, and the extent to which results might depend on analysis-population choices.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| GSK1437173A Vaccine Group | 7 | 62 | 11.3% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| GSK1437173A Vaccine Group | 0 of 62 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| GSK1437173A Vaccine Group | 53 of 62 |
Most frequent serious adverse event terms
| Event term | Organ system | GSK1437173A Vaccine Group |
|---|---|---|
| Acute myocardial infarction | Cardiac disorders | 1 of 62 |
| Atrial fibrillation | Cardiac disorders | 1 of 62 |
| Atrial flutter | Cardiac disorders | 1 of 62 |
| Atrial tachycardia | Cardiac disorders | 1 of 62 |
| Benign prostatic hyperplasia | Reproductive system and breast disorders | 1 of 62 |
| Retroperitoneal haematoma | Gastrointestinal disorders | 1 of 62 |
| Cholecystitis acute | Hepatobiliary disorders | 1 of 62 |
| Septic shock | Infections and infestations | 1 of 62 |
| Cerebrovascular accident | Nervous system disorders | 1 of 62 |
Most frequent non-serious adverse event terms
| Event term | Organ system | GSK1437173A Vaccine Group |
|---|---|---|
| Pain | General disorders | 46 of 62 |
| Fatigue | General disorders | 31 of 62 |
| Myalgia | Musculoskeletal and connective tissue disorders | 29 of 62 |
| Erythema | Skin and subcutaneous tissue disorders | 27 of 62 |
| Headache | Nervous system disorders | 18 of 62 |
| Chills | General disorders | 16 of 62 |
| Swelling | General disorders | 16 of 62 |
| Pyrexia | General disorders | 15 of 62 |
| Gastrointestinal disorder | Gastrointestinal disorders | 11 of 62 |
| Nausea | Gastrointestinal disorders | 1 of 62 |
Serious events with the highest arm-level rate: acute myocardial infarction (1.6%), atrial fibrillation (1.6%), atrial flutter (1.6%), atrial tachycardia (1.6%), benign prostatic hyperplasia (1.6%).
The adverse-event record lists 62 participants at risk for the serious-event count and 7 affected. For other adverse events, it lists 62 at risk and 53 affected. The death count is 0. These are counts in the study group, not comparisons against a control group. The registry record does not give a full account of event timing, duration, recurrence, or participant-level overlap between serious and other event categories.
The listed serious adverse event terms are acute myocardial infarction, atrial fibrillation, atrial flutter, atrial tachycardia, benign prostatic hyperplasia, and retroperitoneal haematoma; each is accompanied by a reported frequency of 1.6%. The record does not state in this listing whether these events were considered related to vaccination. Although a secondary outcome is described as covering serious events related to study participation or a concurrent GSK medication or vaccine, the available group counts do not establish relatedness for individual terms.
In general, an adverse event is not necessarily caused by an intervention. With no concurrent comparison group, these counts are descriptive and cannot establish whether observed events occurred more or less often than they would under another condition.
12. What the Result Does, and Does Not, Mean
The study asks a focused persistence question: what anti-gE antibody concentration was measured at month 108 after the first dose of an earlier 2-dose vaccination course? It also sets out to assess immune responses after later revaccination and to record safety outcomes. These are relevant descriptive aims for a long-term follow-up study, but the registry record does not report the primary GMC or its 95% confidence interval, and it does not provide the listed immune outcome estimates.
Accordingly, the record does not show the size of the antibody response, how precisely it was estimated, or how it changed between time points. It cannot support a conclusion about whether immune response increased, decreased, or remained stable. The listed secondary outcomes are endpoints of interest, not evidence of a particular result. The completed study status does not substitute for posted outcome estimates.
The safety counts show that serious and other adverse events were recorded among participants at risk, and that the reported death count was 0. They do not show whether the vaccine caused or prevented those events. The terms and frequencies listed for serious events are descriptive; their relationship to vaccination is not established by the counts alone.
More broadly, a single-group follow-up cannot provide the same causal comparison as a randomized study with a concurrent control. The group had completed an earlier vaccine course, and the revaccination description includes people receiving 1 or 2 additional doses. The record does not report a comparative analysis of those dose groups. Any interpretation should therefore stay within the descriptive scope of the reported design and posted data.
13. Why This Trial Matters Statistically
This study illustrates a common statistical distinction between defining an outcome and reporting its result. The registry carefully identifies a long-term immune marker, its assay, units, summary measure, time point, and intended confidence interval. Those details establish what the primary endpoint means, but without the estimate, interval, and analysis denominator they do not establish the observed level or its precision.
It also highlights the role of analysis populations in long-term follow-up. The primary persistence endpoint was assigned to an according-to-protocol immunogenicity cohort, while enrollment and revaccination counts describe broader or different sets of participants. These populations should not be assumed interchangeable. Clear outcome-specific denominators and reasons for missing measurements are important for judging whether a reported estimate represents the intended cohort.
Finally, the design helps define what can be learned from safety counts. Counts among participants followed over time can describe what was observed, but without a concurrent comparator they do not quantify a causal difference in risk. The registry’s serious-event terms and frequencies therefore need to be read as descriptive records, not comparative evidence.
The statistical lesson is not that the study lacks value, but that interpretation depends on matching the strength of a claim to the design and the information reported. An endpoint definition, a completed status, and event counts answer different questions from an estimated treatment effect or a controlled safety comparison.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The most direct limitation for interpretation is that the registry record does not report the primary GMC or its 95% confidence interval. It also does not report estimates for the listed secondary immune outcomes. Although the study is marked completed, the outcome definitions alone do not reveal the magnitude or precision of the findings.
The study has no concurrent control group, and it is described as single-group and unmasked. Participants had already completed the earlier vaccination course, so the findings concern a cohort with that prior history. The design does not support a randomized comparison of vaccination strategies. The registry also does not describe a comparative analysis between participants receiving 1 or 2 additional doses.
The primary analysis population is defined as an according-to-protocol immunogenicity cohort, but its size and participant flow are not reported. The record does not state how many measurements were missing, why they were missing, or how missing data were handled. Without those details, the possible influence of selection into the analysis cannot be assessed.
Further limitations include the absence of a reported statistical analysis plan, multiplicity approach, model details, or methods for any repeated measurements. The safety counts are descriptive, and the record does not establish relatedness for the listed serious-event terms. These omissions constrain both statistical assessment and causal interpretation.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study to Evaluate Immunogenicity and Safety of GSK Biologicals' Herpes Zoster Subunit (HZ/su) Vaccine at 9 and 10 Years After Vaccine Administration and Assessment of Re-vaccination With 2 Additional Doses at 10 Years After Initial Vaccination, in Healthy Subjects Aged 60 Years of Age(YOA) and Older — NCT02735915.
- Registry record last updated 2024-04-12; status last verified 2024-04.
- Results first posted 2019-11-01.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT02735915 is a completed phase 3, single-group study of GSK1437173A in healthy subjects aged 60 years and older who had completed a prior 2-dose HZ/su course. Enrollment was 70; the arm description states that 62 subjects received 1 or 2 additional doses during revaccination. The study evaluated immune-response persistence and later revaccination responses, with safety outcomes also listed.
The primary endpoint was anti-gE antibody GMC at month 108 after the first dose of the initial course, measured by ELISA and specified with a 95% confidence interval. The registry lists 14 outcomes and zero analyses. The primary estimate, its interval, and the size of its analysis cohort are not reported in the registry record. Safety counts list 7 of 62 participants affected by serious adverse events, 53 of 62 affected by other adverse events, and 0 deaths.