Study to Demonstrate the Lot-to-lot Consistency and to Evaluate the Safety of an Adjuvanted Influenza Vaccine Candidate: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study to Demonstrate the Lot-to-lot Consistency and to Evaluate the Safety of an Adjuvanted Influenza Vaccine Candidate (NCT00321763), a randomized phase 2 study. The primary outcome is Titers for Serum Hemagglutination Inhibition (HI) Antibodies Against 3 Strains of Influenza Disease..

2. Clinical Question

3. Trial Design

This was a randomized, double-blind, parallel-group phase II trial with a reported enrollment of 3124. The study concerned influenza and enrolled adults aged 60 years or older. Its stated purpose combined examination of consistency across three production lots of an adjuvanted influenza vaccine candidate with evaluation of safety compared with Fluarix. The trial is marked completed in the registry record.

Participants received one dose on Day 0. Three groups received candidate vaccine Lot 1, Lot 2, or Lot 3, each adjuvanted with AS03. The registry also describes a pooled candidate-vaccine group. A separate group received Fluarix; the arm description characterizes it as adjuvanted with AS03 as well. Injections were intramuscular into the deltoid region of the non-dominant arm. The primary antibody outcome was assessed at Days 0 and 21.

Random allocation is intended to reduce systematic differences between groups at the outset, while masking is intended to limit the influence of treatment knowledge on participant experience, care, and assessment. These are general design principles; the registry record does not report how the random sequence was generated, how allocation was concealed, or who was masked. It identifies a parallel-group model, meaning the groups were compared as distinct treatment arms rather than by crossing participants between interventions.

The total enrollment does not establish how many participants contributed to each endpoint. The primary immunogenicity analysis was described as using an According-To-Protocol cohort, and the record does not give its size. It also does not report detailed recruitment, follow-up, or participant-flow information. These omissions matter when judging how closely the analyzed populations correspond to the full randomized trial.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The analysis was performed on the According-To-Protocol (ATP) cohort for immunogenicity which included all evaluable subjects for whom data concerning Immunogenicity outcomes variables were available and for whom assay results were available for antibodies against at least one study vaccine 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 Titers for Serum Hemagglutination Inhibition (HI) Antibodies Against 3 Strains of Influenza Disease., measured over At Days 0 and 21.

The primary outcome concerns serum antibodies that inhibit hemagglutination, a laboratory measure of antibody response to influenza strains. Titers were assessed against A/New Caledonia, A/New York, and B/Malaysia at Day 0 and Day 21. The registry describes results as geometric mean titers, with 95% confidence intervals, and gives a seropositivity assay cut-off of 1:10. The primary efficacy variables were the results for candidate-vaccine Lots 1, 2, and 3 and for the pooled candidate group.

A titer is a measure derived from the laboratory assay; a geometric mean summarizes values on a multiplicative scale. In general, this summary can be useful when measurements are skewed and differences are naturally interpreted as proportional rather than additive. A 95% confidence interval expresses uncertainty around an estimated quantity under the assumptions of the analysis. It is not a range that contains every participant’s response.

For a lot-consistency question, the estimates for separate production lots are relevant because a pooled result can conceal differences among lots. However, the registry record does not report the numerical titers, confidence intervals, or a formal lot-consistency analysis. It therefore does not establish from the posted results whether the lots met any consistency criterion. Nor does an antibody-titer outcome alone describe clinical influenza cases; such outcomes and their results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a geometric mean summarize?

Geometric means are often used for antibody titers because such measurements may vary multiplicatively: a change can be understood in terms of scaling rather than a fixed additive increment. In general, the geometric mean is calculated by working on a logarithmic scale, averaging there, and transforming the estimate back to the original scale. This can make a central summary less dominated by a small number of high values than an arithmetic mean would be. This is a general explanation, not a statement about the analysis performed in this trial. The registry record identifies geometric mean titers as the outcome summaries but does not report the computational details or any resulting estimates.

A 95% confidence interval describes uncertainty in an estimated population quantity under the statistical model and its assumptions. In general, a narrower interval indicates greater precision, while a wider interval indicates greater uncertainty. The interval does not describe the spread of individual participants’ titers, and it does not mean that 95% of participants fall within its limits. The record specifies 95% confidence intervals but provides no numerical intervals for the primary outcome.

Why assess more than one strain and lot?

The antibody outcome covers three strains: A/New Caledonia, A/New York, and B/Malaysia. These are separate measurements, not interchangeable observations of a single outcome. The candidate vaccine was also posted as three production lots. Examining lot-specific results addresses whether the measured responses were similar across those lots; examining a pooled group summarizes the candidate groups collectively. In general, pooling can increase the amount of information used for an overall estimate, but it can obscure variation between the lots. The registry record does not report a formal consistency analysis or its decision criteria, so no method-specific conclusion can be assessed.

What do randomization and masking contribute?

Randomization is intended, in general, to make treatment assignment independent of participants’ known and unknown baseline characteristics on average. It provides a basis for comparing assigned groups, although chance imbalances can still occur. Double masking is intended to reduce the influence of treatment knowledge on behavior, reporting, clinical management, and outcome assessment. The record reports randomized allocation and double masking, but does not report the sequence-generation method, concealment procedures, or which roles were masked. These details cannot be inferred from the design labels.

The parallel-group structure means each participant was assigned to a treatment group for the trial rather than receiving multiple study interventions in sequence. Each described vaccination was a single dose at Day 0. The primary antibody measurements were planned at Day 0 and Day 21. The record does not provide participant-level trajectories or a statistical model for handling the two measurement times.

How should the reported safety counts be interpreted?

Counts of participants affected are descriptive. They do not account by themselves for differing follow-up, baseline risk, or uncertainty, and they do not quantify a comparative treatment effect. A formal comparison would require a defined estimand and analysis, along with adequate information about observation time and event ascertainment. Those details are not reported in the registry record. The listed serious-event count for the pooled candidate group combines the three lot groups; it should not be treated as an independent group alongside the individual lots when interpreting comparisons.

The registry also gives a list of serious adverse-event terms and associated percentages. Without the corresponding event counts and denominator definitions, those percentages cannot be translated into group-specific risks or used to reconstruct a comparison. The record does not report death counts. These limitations are reasons to keep the interpretation descriptive rather than inferential.

What can planning calculations establish?

In general, sample-size planning uses assumptions about the effect to detect, variability, significance level, allocation, and desired power. The planning illustration associated with this trial is described as using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It uses fractions of an observed effect, and the general convention is that non-time-to-event outputs are participants per arm. These are planning assumptions, not observed outcomes and not evidence that the trial had a particular power for its actual result.

The registry record does not report the trial’s own sample-size justification. The planning illustration is explicitly not the trial’s design calculation, and the record does not provide a basis for treating it as one. Since the primary numerical effect estimates are not reported, the planning values should not be read as establishing the trial’s achieved precision or ability to answer the lot-consistency question.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome spans three influenza strains, multiple vaccine lots, a pooled candidate group, and measurements at Days 0 and 21. This creates multiple potential estimates and comparisons. In general, when many hypotheses are tested, the chance of at least one apparently notable result can rise unless the analysis plan accounts for multiplicity. Methods can include prespecifying a hierarchy of tests or adjusting inference across comparisons. The registry record does not report whether any multiplicity strategy was planned or used, nor does it report p-values or formal analyses that could be evaluated for this issue.

The primary immunogenicity population is described as an According-To-Protocol cohort, including evaluable participants with immunogenicity outcome data and assay results for antibodies against at least one study vaccine component. The record does not give the cohort size, exclusions, or reasons for exclusion. It does not report an intention-to-treat analysis population or explain whether additional populations were used for other outcomes.

Missing-data handling is not reported in the registry record. There is no description of how unavailable Day 0 or Day 21 measurements, missing assay results, or incomplete follow-up were handled. The record also does not describe imputation, sensitivity analyses, or assumptions about missingness. These omissions limit assessment of whether the analyzed participants represent all randomized participants and whether missing observations could affect interpretation.

The registry lists ten outcome measures but reports zero analyses. Thus, outcome definitions are available, but the registered information does not supply the analysis results or enough detail to assess adjustment for multiple endpoints, missing observations, or differences between analysis populations.

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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: angina pectoris (0.5%), cerebrovascular accident (0.4%), syncope (0.2%), cholelithiasis (0.2%), constipation (0.2%).

The safety record gives numbers at risk and numbers of participants affected by serious adverse events and by other adverse events for each listed group. Serious adverse events were reported for 30 of 850 participants in Lot 1, 24 of 850 in Lot 2, 23 of 854 in Lot 3, 77 of 2554 in the pooled candidate group, and 21 of 570 in the Fluarix group. These counts should be read as descriptive. The record does not provide comparative estimates, confidence intervals, or a statistical analysis of these events.

The pooled candidate group contains the three lot groups, so it overlaps with the individual lot groups rather than representing an additional independent group. Comparing the pooled count as though it were independent of the lot-specific counts would therefore be misleading. The record also lists serious-event terms and percentages: angina pectoris, 0.5%; cerebrovascular accident, 0.4%; syncope, 0.2%; cholelithiasis, 0.2%; constipation, 0.2%; and coronary artery disease, 0.2%. The underlying counts and percentage denominators are not reported in the registry record.

Death counts are not reported in the registry record. The available safety entries do not provide event timing, duration of follow-up, severity grading beyond the serious-event classification, or a causal assessment. They should not be treated as a complete characterization of safety or as proof of a difference between groups.

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

The registry record establishes that a randomized, double-blind, parallel-group phase II study enrolled adults aged 60 years or older and examined three candidate-vaccine production lots, a pooled candidate group, and Fluarix. It identifies antibody titers against three influenza strains at Days 0 and 21 as the primary outcome and gives selected safety counts. These details describe the questions and measurements registered for the study.

The record does not provide numerical primary antibody results, confidence intervals, p-values, or formal lot-consistency analyses. It therefore does not establish how large the antibody responses were, how precisely they were estimated, whether the candidate lots met a consistency criterion, or how the candidate compared statistically with Fluarix. A study objective is not itself evidence that the objective was achieved.

Likewise, the adverse-event counts are not sufficient to establish a comparative safety conclusion. They are descriptive counts without reported comparative uncertainty or analysis details. Some serious adverse-event terms are listed with percentages, but the underlying counts and denominators are not reported. Death counts are also not reported in the registry record.

In general, laboratory antibody measures can inform understanding of an immune response, but they are not the same as observed clinical outcomes such as influenza illness. The registry record does not report clinical influenza outcomes or provide evidence from which to infer them. Nor does a trial in adults aged 60 years or older automatically establish results for other populations. The reasonable interpretation is therefore narrow: the record describes the design, intended immunogenicity measures, and selected safety information, while leaving the primary numerical findings and key analyses unreported.

13. Why This Trial Matters Statistically

This trial raises two distinct statistical questions. The first is whether measured antibody responses differ across three production lots. The second is how the candidate vaccine’s safety compares with a comparator. Keeping these questions separate is important: pooled summaries can address an overall candidate-group description, but do not by themselves answer whether individual lots are sufficiently similar. The registry identifies lot-specific and pooled outcomes, making the distinction visible, but does not report the results or criteria needed to resolve it.

The design also illustrates why endpoint definitions and analysis populations matter. The primary outcome is a geometric mean titer with a stated confidence-interval measure, assessed against three strains at two time points. The primary analysis is described for an According-To-Protocol cohort rather than simply all enrolled participants. Without numerical results, cohort size, missing-data methods, or a reported analysis plan, readers cannot judge the precision and robustness of estimates.

For safety, the registry gives affected-participant counts for the three lots, a pooled candidate group, and Fluarix. Recognizing that the pooled group overlaps the lot-specific groups prevents treating those entries as independent comparisons. The counts are informative as descriptive record entries, but a comparative conclusion requires more than counts alone. The record’s missing primary findings and absence of reported analyses underscore the difference between a registered research question and an interpretable statistical result.

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 efficacy is that numerical primary-outcome results are not reported in the registry record. Although the outcome, strains, time points, summary measure, and confidence-interval level are described, the actual GMT estimates and intervals are absent. The record also reports no analyses, so there is no formal result for the stated lot-consistency objective or a comparative immunogenicity analysis against Fluarix.

Important design and analysis details are not reported in the registry record. These include the randomization method and allocation concealment, the masking procedures, a lot-consistency margin or decision rule, the trial’s sample-size justification, multiplicity handling, and missing-data methods. The immunogenicity population is described as an According-To-Protocol cohort, but its size and participant flow are not given. Consequently, the extent to which the analysis represents all randomized participants cannot be assessed.

The safety information is also limited. Counts of participants with serious and other adverse events are presented, along with selected serious-event terms and percentages, but comparative analyses, event timing, follow-up details, and percentage denominators are not reported. Death counts are not reported in the registry record. The pooled candidate group overlaps with its individual lot groups, which constrains direct interpretation of the listed counts as separate arms.

Finally, the registered primary measure is an antibody laboratory outcome. Clinical influenza outcomes are not reported in the registry record, so the immunogenicity description cannot be extended to claims about clinical disease outcomes. These limitations concern the information available in the registry record and do not establish what may have appeared in other sources.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Study to Demonstrate the Lot-to-lot Consistency and to Evaluate the Safety of an Adjuvanted Influenza Vaccine Candidate — NCT00321763.
• Registry record last updated 2018-06-08; status last verified 2016-09.
• Results first posted 2013-06-24.
• 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 record describes a completed, randomized, double-blind, parallel-group phase II study with enrollment of 3124 adults aged 60 years or older. Participants received one intramuscular dose of one of three AS03-adjuvanted GSK1247446A production lots or Fluarix. The primary outcome was geometric mean serum hemagglutination-inhibition antibody titers against A/New Caledonia, A/New York, and B/Malaysia at Days 0 and 21, with 95% confidence intervals. The primary variables were the three lot groups and pooled candidate group.

Safety entries report serious and other adverse-event counts by group, as well as selected serious-event terms and percentages. Numerical primary antibody results, formal analyses, multiplicity methods, missing-data procedures, and the trial’s own sample-size justification are not reported in the registry record. The available information therefore describes the study design and selected outcomes but does not provide a statistical conclusion about lot consistency or comparative immunogenicity.