A Study of Immunogenicity and Safety of GSK Biologicals' Influenza Vaccine FLU-Q-QIV in Adults Aged 18 Years and Older: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of Immunogenicity and Safety of GSK Biologicals' Influenza Vaccine FLU-Q-QIV in Adults Aged 18 Years and Older (NCT01440387), a non-randomized phase 3 study. The primary outcome is Humoral Immune Response in Terms of Hemagglutination Inhibition (HI) Antibodies Against Each of the 4 Vaccine Influenza Strains..

2. Clinical Question

3. Trial Design

This was a Phase IIIA study of FLU-Q-QIV, described in the registry as FLULAVAL® QUADRIVALENT. The study was completed and enrolled 112 participants. The registry records a start date of 2011-09-30 and a primary completion date of 2011-10-22.

The design was parallel and non-randomized, with no masking. Participants were described in two groups: adults aged 18-60 years and adults above 60 years. Each group received one dose at Day 0. The vaccine was administered intramuscularly in the deltoid of the non-dominant arm. The groups each had 56 participants listed in the safety record.

The registry does not describe a separate control group. Because age group was not randomly assigned and both groups received the vaccine, differences between their outcomes cannot be interpreted as a randomized estimate of a treatment effect. The study can describe the recorded immune and safety outcomes in these enrolled groups, subject to the completeness of the posted results.

The primary outcome concerned hemagglutination inhibition antibodies against four vaccine strains, assessed at Day 0 and Day 21. Secondary outcomes listed solicited local and general symptoms, unsolicited adverse events, and serious adverse events. Detailed protocol procedures, a sample-size justification, and a full statistical analysis plan are not reported in the registry record.

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

Analysis population for the primary outcome, as defined in the registry: The analyses were performed on According-to-Protocol (ATP) cohort for immunogenicity, which included all evaluable subjects for whom data concerning immunogenicity outcome measures were available. These included subjects for whom assay results were available for antibodies against at least one study vaccine antigen component after vaccination.

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.

6. Primary Endpoint

The registry lists the primary outcome as Humoral Immune Response in Terms of Hemagglutination Inhibition (HI) Antibodies Against Each of the 4 Vaccine Influenza Strains., measured over At Day 0 and Day 21.

The primary endpoint measures humoral immune response using hemagglutination inhibition (HI) antibody titers against each of the four vaccine influenza strains. The strains named in the record are Flu B/Florida/4/06 (Yamagata), FluB/Bri/60/08 (Victoria), Flu A/CAL/7/09 (H1N1), and Flu A/Victoria/210/09 (H3N2) antigens. Measurements were planned at Day 0 and Day 21.

The registry describes the summary measure as a geometric mean titer (GMT), with a 95% confidence interval. In general, a GMT summarizes antibody titers using their geometric rather than arithmetic mean, which is useful for measurements that vary across a multiplicative scale. A confidence interval conveys uncertainty around an estimated mean; it is not a guarantee that the true value lies within the interval.

HI antibody titers are an immunogenicity measure: they describe an antibody response measured by the assay. Such a measure is distinct from a clinical outcome, such as influenza illness. The record does not report numerical GMTs or confidence intervals, so the size and precision of the observed immune response cannot be assessed from the registry results. It also does not report a prespecified threshold for interpreting the titers.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

In general, an immunogenicity analysis describes immune measurements rather than directly estimating a clinical treatment effect. This study’s primary measurement was the HI antibody titer for each of four influenza strains. The record specifies GMTs and 95% confidence intervals at Day 0 and Day 21. It does not report the observed estimates, the number analyzed for each strain, or the calculations used to produce them.

What does a geometric mean summarize?

In general, a geometric mean is a way to summarize positive measurements that are naturally interpreted on a multiplicative scale. The calculation is based on the mean of log-transformed values and then transformed back to the original scale. It can provide a central summary when values vary over a wide range. This general description does not establish the precise analysis procedure used in this study; that procedure is not reported in the registry record.

A GMT is a group-level summary, not a description of every participant’s titer. It does not show the spread of individual values by itself. Additional information such as the distribution of titers, participant-level changes, and the count of observations contributing to each estimate would help readers understand the data, but these details are not reported in the registry record.

How should the confidence interval be read?

In general, a confidence interval expresses the statistical uncertainty around an estimated quantity under the assumptions of the method used. A narrower interval indicates greater precision than a wider interval, all else being equal. It does not describe the range containing most individual participants’ results, and it does not represent the probability that a particular treatment effect is true. The registry identifies 95% confidence intervals as the dispersion measure, but their numerical limits are not reported in the registry record.

Comparing confidence intervals is not automatically equivalent to performing a formal hypothesis test. A formal comparison would require a defined contrast and an analysis method. The record does not report a primary hypothesis test, a test statistic, a p-value, or a prespecified decision criterion for the immune response.

What does the design permit?

In general, random allocation can help balance measured and unmeasured participant characteristics across treatment groups. This study is recorded as non-randomized and has no masking. Its two parallel groups are age-defined cohorts receiving the same vaccine, not randomized vaccine and control groups. Accordingly, comparisons between the cohorts are descriptive unless a suitable analysis and assumptions are specified; no such comparative analysis is reported in the registry record.

The record lists 112 enrolled participants and safety denominators of 56 in each age group. Those enrollment and safety counts do not establish how many participants contributed to each immunogenicity estimate. The ATP cohort definition indicates that evaluability and availability of assay data mattered for inclusion, but the handling of missing measurements and exclusions is not reported in the registry record.

What information is needed for a fuller assessment?

A complete statistical account would usually describe the analysis population for each outcome, the handling of missing observations, the methods used for estimation, and any planned comparisons. For multiple outcomes or strain-specific analyses, a plan may also explain how the risk of false-positive findings is addressed. These are general features of statistical reporting; the registry record does not provide the study’s detailed analysis plan or report whether multiplicity adjustments were used.

The record lists eight outcome measures and no analyses. The absence of reported analysis results means the available record cannot support numerical assessment of primary-endpoint precision, tests of change, or comparisons between age groups. No sample-size justification, interim-analysis plan, or detailed model specification is reported in the registry record. Any sample-size illustration based on an observed effect would be a planning illustration, not observed power; the posted record does not provide primary effect estimates on which to base such an interpretation.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome covers four vaccine strains, and the record also lists several safety outcomes. When multiple outcomes or strain-specific estimates are examined, the chance of finding an apparently notable result by chance can increase. In general, a prespecified analysis plan may define the main comparisons and describe any method for addressing multiplicity. The registry record does not report a multiplicity strategy, a hierarchy of outcomes, or which strain-specific result would be considered primary if they differed.

The record identifies an ATP cohort for immunogenicity, described as including evaluable participants with available immunogenicity data and assay results for antibodies against at least one study antigen. The description is truncated, and the number included in the cohort is not reported in the registry record. The number with results for each strain and time point, reasons for exclusion, and handling of missing measurements are also not reported in the registry record.

There are no posted numerical primary-endpoint results or analyses in the registry record. It does not report whether any interim analyses occurred, the statistical testing plan, or the approach used to calculate the confidence intervals. A sample-size justification is not reported in the registry record. The listed enrollment alone cannot show whether the study was planned to estimate immune responses with a particular precision or to test a specified hypothesis.

For safety outcomes, the registry lists counts but does not describe how incomplete follow-up or missing safety information was handled. These reporting gaps limit assessment of both the completeness of the outcome data and the possibility that exclusions or missing observations affected the summaries.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent non-serious adverse event terms

The safety record lists zero participants with serious adverse events among 56 in the Adult Group and zero among 56 in the Elderly Group. These are observed counts in the enrolled groups, not evidence that serious adverse events are impossible or that the risk is absent. With no serious events listed, the record provides no event-specific information about serious adverse events. The list of serious adverse event terms is empty.

The record also lists other adverse events for 46 participants in the Adult Group and 28 in the Elderly Group. Those counts should be kept distinct from the serious adverse event counts; they do not indicate that the events were serious. The registry separately lists outcomes concerning solicited symptoms, unsolicited adverse events, and related serious adverse events, but does not provide detailed event descriptions or numerical outcome results for each listed measure.

Deaths are not reported in the registry record. The safety information should therefore be read as a limited set of posted counts rather than a complete account of the nature, timing, severity, or relationship of all events.

12. What the Result Does, and Does Not, Mean

The study was designed to evaluate immunogenicity and safety after a dose of FLULAVAL® QUADRIVALENT in adults aged 18 years and older. The primary outcome was an antibody measurement against four vaccine strains at Day 0 and Day 21. The registry record does not report the numerical GMTs or confidence intervals, so it cannot show the size or precision of the antibody measurements.

Even if numerical antibody results were available, an immune measurement would not by itself establish how the vaccine affects clinical influenza outcomes. The record identifies an immunogenicity endpoint, not a clinical efficacy endpoint. No conclusion about prevention of illness or other clinical benefit can be drawn from the endpoint description alone.

The two groups are defined by age and were not randomized. Both received the vaccine, and the record does not describe a separate control group. Consequently, the design does not provide a randomized comparison of vaccine versus no vaccine or another intervention. Nor should any difference between the age groups be interpreted as caused by age without further design and analysis information.

The safety record lists no serious adverse events in either group, alongside counts for other adverse events. These observations describe what is listed for this study; they cannot establish the absence of risk beyond the participants and follow-up represented in the record. The registry does not report deaths, detailed event descriptions, or comprehensive safety analyses.

The most defensible interpretation is therefore limited: the registry documents the study’s design and intended outcome measures, with some safety counts, but does not provide the primary numerical immune-response results needed to assess the endpoint itself. The record also lacks detail about the statistical analysis and missing data.

13. Why This Trial Matters Statistically

This study illustrates why an outcome definition and a numerical result are different kinds of information. The registry describes a specific immunogenicity measure—HI antibody titers summarized as GMTs with 95% confidence intervals—but does not post the corresponding estimates. Without those estimates, readers cannot assess the observed response or its precision, even though the endpoint and time points are identified.

The design also matters when interpreting comparisons. The Adult Group and Elderly Group provide age-specific cohorts, but they were not formed through random allocation and there is no separate control group in the record. Statistical description of groups is not the same as a controlled treatment comparison. This distinction is important whenever results from parallel cohorts might otherwise be read as evidence of a causal difference.

Finally, the record demonstrates the role of reporting completeness in statistical interpretation. The ATP population is described only in part, while the cohort size for immunogenicity, missing-data procedures, and analysis methods are not reported. Safety counts are available, but event detail and death information are not. These limits do not change the study’s stated question; they define how much can be learned from the registry record.

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 principal limitation for interpreting the primary outcome is that numerical GMTs and 95% confidence intervals are not reported in the registry record. The number of participants contributing to each strain-specific result is also not reported, so the precision and completeness of the immunogenicity summaries cannot be evaluated.

The study was non-randomized and unmasked, and the record does not describe a separate control group. Its age-defined cohorts therefore do not support a randomized treatment comparison. The registry does not report whether or how any comparisons between these cohorts were adjusted for differences in participant characteristics.

The ATP cohort description is incomplete. Exclusion criteria, reasons for missing assay results, and methods for handling missing data are not reported in the registry record. The statistical analysis plan, sample-size justification, interim analyses, and multiplicity approach are also not reported.

Safety reporting is limited to counts. The registry does not report detailed event descriptions, timing, severity beyond the serious-event category, or death counts. It is therefore not possible to assess the full context of the recorded adverse events from these counts alone.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study of Immunogenicity and Safety of GSK Biologicals' Influenza Vaccine FLU-Q-QIV in Adults Aged 18 Years and Older — NCT01440387.
• Registry record last updated 2018-09-07; status last verified 2016-08.
• Results first posted 2013-11-19.
• 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.

18. Record Summary

The registry describes a completed Phase IIIA, parallel, non-randomized, unmasked study of FLULAVAL® QUADRIVALENT in adults aged 18 years and older. It enrolled 112 participants in an Adult Group aged 18-60 years and an Elderly Group above 60 years; each received one dose at Day 0.

The primary outcome was HI antibody titers against four vaccine strains at Day 0 and Day 21, summarized as GMTs with 95% confidence intervals. Numerical primary-outcome results are not reported in the registry record. The safety record lists zero serious adverse events in each group, with 56 participants at risk per group. Further analysis details, missing-data methods, and a sample-size justification are not reported in the registry record.