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 Clinical Study of the Immunogenicity of GSK Biologicals' Influenza Vaccine GSK2186877A in People Aged 65 Years or Older (NCT00765076), a randomized phase 3 study. The primary outcome is The Geometric Mean (GM) Number of Influenza-specific CD4 T-cells Per Million CD4+ T-cells Identified After in Vitro Stimulation With Pooled Vaccine Strains Which Are Producing at Least Two Different Markers.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00765076 |
| Phase | Phase 3 |
| Condition | Influenza |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 192 |
| Arms in the primary outcome | 3 |
| Lead sponsor | GlaxoSmithKline |
| Results posted | Yes |
2. Clinical Question
Population
The primary endpoint analysis included evaluable participants aged 65 years or older in the According-to-Protocol immunogenicity cohort, for whom immunogenicity data were available. The registry reports that this endpoint analysis covered the GSK2186877A and elderly Fluarix groups. The Fluarix young group consisted of participants aged 18-40 years and was not included in the primary endpoint analysis.
Intervention
One dose of GSK Biologicals’ influenza vaccine GSK2186877A was given at Day 0 to the older-adult intervention group.
Comparator
The primary endpoint comparison was with the elderly Fluarix group, which received one dose of Fluarix at Day 0. A separate young Fluarix group was also enrolled, but it was not part of this primary endpoint analysis.
Primary question
At Day 21, what was the geometric mean number of influenza-specific CD4 T-cells per million CD4+ T-cells producing at least two different immune markers after stimulation with pooled vaccine strains?
This is an immunogenicity question: it concerns a measured cellular immune response rather than a clinical influenza outcome. The endpoint is a group-level summary of cells identified after laboratory stimulation. The registry’s reported summaries permit descriptive comparison between the two older-adult groups, but they do not include an inferential estimate of the difference or its uncertainty. The record does not report a primary question about protection from influenza illness.
3. Trial Design
The registry describes a Phase 3, randomized, triple-masked, parallel-group study of influenza-vaccine immunogenicity. It lists an enrollment of 192 and a completed status. The study start date is 2008-10-16, and the primary completion date is 2009-12-04. Influenza is the listed condition, and GlaxoSmithKline is the listed sponsor.
The intervention groups were the GSK2186877A group, the elderly Fluarix group, and the young Fluarix group. Participants in each group received one dose at Day 0. The two older-adult groups were described as age 65 years or older; the young Fluarix group was described as aged 18-40 years. The registry’s primary immunogenicity analysis was restricted to the two older-adult groups. The young group appears among the trial arms and safety summaries, but it has no reported value for the primary endpoint.
The official title calls the study observer-blind, while the registry’s masking classification is triple. Which individuals or roles were masked is not reported in the registry record, so the masking classification should not be expanded into assumptions about who knew treatment assignment. The allocation is identified as randomized, but details of the randomization sequence, allocation concealment, and assignment procedures are not reported in the registry record.
The registry does not report the rationale for the enrollment target, the planned group sizes, or whether the study included interim analyses. It also does not describe the operational details of vaccine administration beyond one dose at Day 0. These omissions limit reconstruction of the trial’s planned conduct from the registry entry alone.
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.
Overall Study
| Stage | New Generation Influenza Vaccine GSK2186877A Group | Fluarix Elderly Group | Fluarix Young Group |
|---|---|---|---|
| STARTED | 69 | 73 | 50 |
| COMPLETED | 68 | 73 | 49 |
| NOT COMPLETED | 1 | 0 | 1 |
Reasons for not completing this period:
| Reason | New Generation Influenza Vaccine GSK2186877A Group | Fluarix Elderly Group | Fluarix Young Group |
|---|---|---|---|
| Adverse Event | 1 | 0 | 0 |
| Withdrawal by Subject | 0 | 0 | 1 |
Analysis population for the primary outcome, as defined in the registry: Analysis was performed on According-to-Protocol (ATP) Immunogenicity cohort. This cohort included all evaluable subjects for whom data concerning immunogenicity were available. Analysis was only performed for New generation influenza vaccine GSK2186877A Group and Fluarix elderly Group.
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 | New Generation Influenza Vaccine GSK2186877A Group | Fluarix Elderly Group | Fluarix Young Group | Total |
|---|---|---|---|---|---|
| Participants analysed | 69 | 73 | 50 | 192 | |
| Age, Continuous | Years | 71.5 (SD 5.44) | 71.5 (SD 5.32) | 26.0 (SD 4.91) | 59.7 (SD 20.69) |
| Sex: Female, Male: Female | Participants | 36 | 29 | 27 | 92 |
| Sex: Female, Male: Male | Participants | 33 | 44 | 23 | 100 |
6. Primary Endpoint
The registry lists the primary outcome as The Geometric Mean (GM) Number of Influenza-specific CD4 T-cells Per Million CD4+ T-cells Identified After in Vitro Stimulation With Pooled Vaccine Strains Which Are Producing at Least Two Different Markers, measured over Day 21.
| Element | Registry entry |
|---|---|
| Result type | Geometric Mean |
| Measure of spread | Standard Deviation |
| Unit | cells per million CD4+ Tcells |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the geometric mean number of influenza-specific CD4 T-cells per million CD4+ T-cells identified after in vitro stimulation with pooled vaccine strains and producing at least two different markers. The markers assessed were CD40L, IL-2, TNF-α, and IFN-γ. The measurement was taken at Day 21, and the unit was cells per million CD4+ T-cells.
In general, a geometric mean is a way of summarizing positive measurements when values can vary substantially across participants. It uses multiplicative rather than additive averaging and can be useful when a distribution is uneven or right-skewed. This is a general statistical explanation; the registry does not report the distribution of individual endpoint measurements or explain why this summary was selected.
The endpoint counts cells meeting a laboratory definition that combines influenza-specific stimulation with expression of multiple immune markers. It is therefore a cellular immunogenicity measure, not a direct count of infections prevented or a measure of clinical disease. The registry lists standard deviations alongside the group geometric means, but does not report confidence intervals for the group means or a formal between-group estimate. The endpoint’s relevance is limited to the immune response it measures; its relationship to clinical outcomes is not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
For the primary endpoint, the registry reports a geometric mean of 3371 cells per million CD4+ T-cells for the GSK2186877A group, based on 62 participants, with a standard deviation of 3602. For the elderly Fluarix group, it reports a geometric mean of 2108 cells per million CD4+ T-cells, based on 61 participants, with a standard deviation of 1728. These are descriptive group summaries for the Day 21 endpoint in the According-to-Protocol immunogenicity cohort.
The reported geometric mean is numerically higher in the GSK2186877A group than in the elderly Fluarix group. That description alone does not establish that the groups differ beyond sampling variability. The registry does not report a between-group effect estimate, confidence interval, p-value, or adjusted analysis for this endpoint. The size and precision of any underlying treatment contrast therefore cannot be determined from the posted endpoint summaries alone.
The standard deviations describe variability in the endpoint data as reported by the registry. The larger standard deviation in the GSK2186877A group indicates greater reported spread under that summary, but standard deviations and geometric means do not give a complete picture of the distributions. The registry does not provide participant-level values, distribution plots, or further measures of dispersion for this endpoint. It is not possible to assess from the summaries whether unusual values, skew, or differences in distribution shape influenced the group statistics.
The primary analysis excludes the young Fluarix group by definition in the registry description. No primary endpoint value is reported for that group, so the older-adult endpoint summaries should not be read as a three-group comparison. The young group’s presence in the trial does not make it a comparator for the stated primary question.
The registry reports enrollment of 192, while the primary endpoint summaries are based on 62 and 61 participants in the two older-adult groups. These are different quantities: enrollment describes the study overall, while the endpoint counts describe the analyzed participants for this particular measure. The registry defines the analysis cohort as evaluable participants with immunogenicity data available. It does not report how many otherwise eligible participants lacked endpoint data, why any data were unavailable, or how missing measurements were handled.
The summaries are compatible with a descriptive statement that the observed group means differed numerically. They do not supply the uncertainty estimates needed for a formal inferential conclusion. No clinical outcome is reported as the primary endpoint, and this cellular response summary does not itself quantify protection against influenza illness.
9. Statistical Methods Explained
What does a geometric mean summarize?
In general, a geometric mean summarizes a set of positive measurements by averaging on a multiplicative scale and expressing that average on the original scale. It can be informative when values span a wide range or when proportional changes are more natural to describe than fixed additive changes. This is a general explanation, not a claim about the distribution in this trial. The registry reports geometric means but does not give the individual observations or a rationale for choosing this summary.
For the primary endpoint, the geometric means are 3371 for the GSK2186877A group and 2108 for the elderly Fluarix group. The associated analyzed counts are 62 and 61, respectively. Those values describe the groups in the stated immunogenicity cohort; they do not by themselves estimate the uncertainty around a contrast between groups.
How should the standard deviations be read?
A standard deviation is a measure of spread around a summary, with its interpretation depending on the scale and statistical method used. In general, more spread means observations vary more within the group, but a standard deviation is not a confidence interval and does not directly measure the precision of the difference between two group summaries. The registry labels the dispersion as standard deviation and reports 3602 for the GSK2186877A group and 1728 for the elderly Fluarix group. It does not specify further details about the scale on which this dispersion was calculated. The values should therefore be read as the registry’s reported spread measures, without making assumptions about their calculation.
Why does a group summary not establish a treatment contrast?
A comparison of group means is distinct from a statistical analysis of the between-group contrast. A confidence interval for a contrast would show a range of values compatible with the data under the analysis assumptions, while a p-value would quantify how unusual the observed data would be under a specified null model. Neither type of inferential result is reported for this primary endpoint. A formal comparison could also depend on analysis choices, such as the model, handling of missing measurements, and any adjustment for other factors. Those choices are not reported in the registry record.
Randomized allocation can support a comparison between assigned groups, but randomization does not remove the need to report the analysis and its uncertainty. The registry identifies the study as randomized and provides group-level endpoint summaries. It does not provide a model-based or otherwise inferential comparison from which the precision of the contrast could be assessed.
What does over-dispersion mean in general?
In general, over-dispersion occurs when variability in observed data exceeds what a chosen statistical model assumes. If a model underestimates variability, standard errors may be too small and confidence intervals too narrow. This concept matters particularly for count outcomes and other data whose variability may not match a simple model. The registry does not report a model for this endpoint, an assessment of over-dispersion, or a reason to conclude that over-dispersion was present. The endpoint’s cell-count unit does not by itself establish which statistical model should be used.
How do planning illustrations differ from observed results?
Sample-size calculations are planning exercises, not observations from the trial. The planning assumptions described for the page use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the target effect is defined as a stated fraction of the observed effect. These assumptions are not reported as the original trial’s design plan. A calculation based on an observed effect is not observed power and should not be interpreted as evidence that the trial was adequately powered. The registry does not report the trial’s own sample-size justification or planned effect size.
In general, planning counts depend on assumptions about the effect to detect, variability, allocation, and analysis. Changing those assumptions can change the implied number of participants. The registry does not report an original calculation that would show how the enrollment target of 192 was chosen. Planning illustrations can help explain the scale of a future study under stated assumptions, but they do not replace a prespecified design rationale or an inferential result from the completed trial.
What can be inferred from the available reporting?
The registry supports a description of the endpoint definition, analysis cohort, group geometric means, group counts, and reported standard deviations. It does not report a treatment-effect estimate, confidence interval, p-value, statistical model, or adjustment strategy for the primary endpoint. Without those elements, readers cannot determine the inferential precision of the between-group contrast from the registry record. In general, statistical significance and practical importance are separate questions: an inferential test concerns compatibility with a statistical model, while practical importance depends on the meaning of the endpoint and its relationship to relevant outcomes. The registry does not provide a threshold for interpreting a meaningful difference in this cellular measure.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 15 secondary outcome measures in addition to the primary outcome. These cover influenza-specific CD4 T-cell measures, haemagglutinin inhibition antibody titers and related serological summaries, and solicited local adverse events. Multiple outcomes create a general multiplicity issue: when many hypotheses are tested, the chance of at least one apparently notable result can increase unless the analysis plan accounts for the number and structure of comparisons. The registry record does not report whether a multiplicity adjustment was planned or applied, or which outcomes were designated for formal hypothesis testing.
No inferential analyses are listed for the primary or secondary outcomes in the analysis record. The registry provides group-level primary endpoint summaries, but does not provide p-values or confidence intervals for the primary comparison. The analysis methods for secondary outcomes are not reported in the registry record. No interim analyses or stopping rules are reported.
The primary endpoint population is the According-to-Protocol immunogenicity cohort, defined as evaluable participants with immunogenicity data available. That definition identifies who was included, but does not describe how exclusions were decided or how missing endpoint measurements were handled. The number of missing measurements, their reasons, and any sensitivity analyses are not reported in the registry record. The registry also does not report a separate intention-to-treat analysis for this endpoint.
These reporting gaps matter because analysis populations and missing-data decisions can affect the interpretation of a group comparison. They should not be filled in by assuming a particular protocol or analysis plan. The results available for this endpoint are best understood as summaries for the stated cohort, with the effect of missingness and multiplicity not assessable from the registry record.
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 |
|---|---|---|---|
| New Generation Influenza Vaccine GSK2186877A Group | 5 | 69 | 7.2% |
| Fluarix Elderly Group | 11 | 73 | 15.1% |
| Fluarix Young Group | 1 | 50 | 2.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| New Generation Influenza Vaccine GSK2186877A Group | 53 of 69 |
| Fluarix Elderly Group | 27 of 73 |
| Fluarix Young Group | 43 of 50 |
Most frequent serious adverse event terms
| Event term | Organ system | New Generation Influenza Vaccine GSK2186877A Group | Fluarix Elderly Group | Fluarix Young Group |
|---|---|---|---|---|
| Abdominal hernia | Gastrointestinal disorders | 1 of 69 | 0 of 73 | 0 of 50 |
| Amnesia | Nervous system disorders | 0 of 69 | 1 of 73 | 0 of 50 |
| Anaemia | Blood and lymphatic system disorders | 1 of 69 | 0 of 73 | 0 of 50 |
| Arrhythmia | Cardiac disorders | 0 of 69 | 1 of 73 | 0 of 50 |
| Atrial flutter | Cardiac disorders | 1 of 69 | 0 of 73 | 0 of 50 |
| Brain neoplasm | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 0 of 69 | 1 of 73 | 0 of 50 |
| Cholecystitis acute | Hepatobiliary disorders | 0 of 69 | 1 of 73 | 0 of 50 |
| Hypersensitivity | Immune system disorders | 0 of 69 | 0 of 73 | 1 of 50 |
| Ligament rupture | Injury, poisoning and procedural complications | 0 of 69 | 1 of 73 | 0 of 50 |
| Lymphoma | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 0 of 69 | 1 of 73 | 0 of 50 |
Most frequent non-serious adverse event terms
| Event term | Organ system | New Generation Influenza Vaccine GSK2186877A Group | Fluarix Elderly Group | Fluarix Young Group |
|---|---|---|---|---|
| Pain | General disorders | 43 of 69 | 15 of 73 | 35 of 50 |
| Fatigue | General disorders | 22 of 69 | 12 of 73 | 21 of 50 |
| Headache | General disorders | 22 of 69 | 7 of 73 | 14 of 50 |
| Myalgia | General disorders | 17 of 69 | 8 of 73 | 11 of 50 |
| Arthralgia | General disorders | 14 of 69 | 3 of 73 | 4 of 50 |
| Gastrointestinal symptoms | General disorders | 6 of 69 | 4 of 73 | 6 of 50 |
| Shivering | General disorders | 11 of 69 | 0 of 73 | 2 of 50 |
| Swelling | General disorders | 8 of 69 | 1 of 73 | 0 of 50 |
| Nasopharyngitis | Infections and infestations | 2 of 69 | 2 of 73 | 4 of 50 |
| Redness | General disorders | 5 of 69 | 0 of 73 | 0 of 50 |
Serious events with the highest arm-level rate: hypersensitivity (2.0%), abdominal hernia (1.4%), anaemia (1.4%), atrial flutter (1.4%), meningioma (1.4%).
The registry reports serious adverse events for each of the three groups. In the GSK2186877A group, 5 participants were affected among 69 at risk. In the elderly Fluarix group, 11 were affected among 73 at risk. In the young Fluarix group, 1 was affected among 50 at risk. These are counts of participants with serious adverse events and the corresponding reported group denominators; they are not estimates of a causal treatment effect.
The registry also lists serious-event terms with percentages: Hypersensitivity, 2.0%; Abdominal hernia, 1.4%; Anaemia, 1.4%; Atrial flutter, 1.4%; Meningioma, 1.4%; and Myocardial infarction, 1.4%. The record does not identify those terms by treatment group in the listed summary, so they should not be assigned to a particular group. It also does not provide details about event timing, duration, or relatedness to vaccination.
Death counts are not reported in the registry record. General caution is warranted when reading adverse-event summaries: counts do not by themselves establish whether an event was caused by an intervention, and differences across groups can be influenced by the number and characteristics of participants observed. The record does not report enough detail to make a causal safety comparison.
12. What the Result Does, and Does Not, Mean
The posted primary endpoint summaries describe cellular immune responses at Day 21 in the two older-adult groups. The geometric mean was 3371 cells per million CD4+ T-cells in the GSK2186877A group and 2108 in the elderly Fluarix group. The values are descriptive summaries for the According-to-Protocol immunogenicity cohort, with standard deviations of 3602 and 1728, respectively.
These figures do not establish whether the groups differ statistically. The registry does not report an inferential comparison, confidence interval, or p-value for the primary endpoint. Without such information, the precision of the observed contrast cannot be assessed. The summaries also do not establish that any observed difference is clinically meaningful; no threshold for meaningful change is reported.
The endpoint measures cells identified by laboratory stimulation and marker expression. It is not a direct measure of influenza cases, severe illness, hospitalization, or another clinical outcome. The record does not report a connection between this particular cellular endpoint and clinical protection. It would therefore be inappropriate to translate the numerical summaries into a claim about prevention of influenza or clinical benefit.
The trial included a young Fluarix group, but the primary endpoint analysis was performed only for the GSK2186877A and elderly Fluarix groups. The young group’s primary endpoint result is not reported in the registry record. Its presence in other trial summaries does not extend the primary endpoint comparison to all three groups.
The interpretation is also limited by reporting of the analysis population and missing data. The registry defines the analyzed cohort as evaluable participants with available immunogenicity data, but does not describe exclusions, missingness, or sensitivity analyses. These limitations do not negate the descriptive results; they define what those results can support. The record documents group-level immunogenicity measurements, not a complete inferential or clinical assessment.
13. Why This Trial Matters Statistically
This trial illustrates the distinction between an endpoint summary and a treatment comparison. A geometric mean gives a concise description of each group, while an inferential contrast addresses how precisely the groups differ under a specified analysis. The registry supplies group summaries for the primary endpoint but no confidence interval, p-value, or treatment-effect estimate. Readers can describe the numerical pattern, but cannot derive the uncertainty of the contrast from the reported summaries alone.
It also highlights the importance of defining the population behind an estimate. The primary outcome was analyzed in an According-to-Protocol immunogenicity cohort rather than being reported for every enrolled participant. The registry gives the analyzed counts and defines the cohort in general terms, but does not explain exclusions or missing data. Those details are important for judging how closely the analyzed participants represent the randomized groups.
The presence of a young comparison group alongside two older-adult groups is another design feature that requires attention to the endpoint-specific analysis. The primary endpoint description names only the older-adult groups. Treating all trial arms as if they answered the same primary question would obscure that distinction.
Finally, this record demonstrates why immunogenicity measures and clinical outcomes should not be conflated. A laboratory measure of influenza-specific CD4 T-cells may characterize a component of immune response, but it is not itself a count of clinical influenza outcomes. The registry does not report a link between the endpoint and clinical protection. Careful statistical interpretation therefore depends on keeping the measured endpoint, its analysis population, and its inferential limits distinct.
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 registry does not report a formal statistical comparison for the primary endpoint. Although it gives geometric means, analyzed counts, and standard deviations for the two older-adult groups, it provides no confidence interval, p-value, or treatment-effect estimate. The precision of the between-group comparison cannot be evaluated from the reported results.
Important design and analysis details are also absent. The randomization sequence, allocation concealment, identities of masked roles, original sample-size justification, statistical model, multiplicity strategy, and interim-analysis plans are not reported in the registry record. The endpoint description identifies an According-to-Protocol immunogenicity cohort, but the record does not explain exclusions from that cohort or how missing measurements were treated.
The primary endpoint has no reported value for the young Fluarix group, because the listed endpoint analysis included only the two older-adult groups. Thus, the primary results do not support a three-group comparison. In addition, the primary endpoint is a laboratory cellular immunogenicity measure. The registry does not report a clinical outcome linked to the measure or a threshold for interpreting its clinical importance.
Safety reporting is similarly limited for causal interpretation. Serious adverse event counts are listed, but details such as event timing, relatedness, and group-specific attribution for the listed serious-event terms are not reported. Death counts are not reported in the registry record. These limitations are specific to the available registry information and do not imply that unreported procedures or analyses were absent from the full study documentation.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Clinical Study of the Immunogenicity of GSK Biologicals' Influenza Vaccine GSK2186877A in People Aged 65 Years or Older — NCT00765076.
- Registry record last updated 2018-07-31; status last verified 2016-10.
- Results first posted 2012-04-05.
- 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
The registry describes a completed, randomized, triple-masked, parallel-group Phase 3 influenza-vaccine immunogenicity study sponsored by GlaxoSmithKline, with enrollment of 192. Participants received one dose at Day 0 in the GSK2186877A, elderly Fluarix, or young Fluarix group. The primary endpoint was the geometric mean number of influenza-specific CD4 T-cells per million CD4+ T-cells producing at least two markers after stimulation with pooled vaccine strains, measured at Day 21.
For the primary endpoint, the registry reports group summaries for the According-to-Protocol immunogenicity cohort: 3371 for GSK2186877A and 2108 for elderly Fluarix, with analyzed counts of 62 and 61. It does not report an inferential comparison or confidence interval. The primary endpoint analysis did not include the young Fluarix group. Important details on missing data, multiplicity, and the original sample-size rationale are not reported in the registry record.