Clinical Trial to Evaluate the Immunogenicity of an Adjuvanted Influenza Vaccine Among HCP: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical Trial to Evaluate the Immunogenicity of an Adjuvanted Influenza Vaccine Among HCP (NCT06054269), a randomized phase 3 study. The primary outcome is Hemagglutination Inhibition (HI) Geometric Mean Titers (GMT) Post-vaccination (Day 28) of Each Vaccine Reference Virus.

2. Clinical Question

The comparison concerns humoral immune responses, measured with an HI assay, rather than a reported clinical influenza outcome. Both arms are described as receiving a single dose of an egg-based quadrivalent vaccine, with adjuvanted and standard-dose formulations distinguished by the named products. The primary endpoint is assessed at 28 days post-vaccination. The registry record does not report a primary hypothesis, a threshold for a clinically important difference, or a single summary contrast combining the virus-specific results. As a result, the clinical question that can be described from the record is whether the measured post-vaccination titers differ by vaccine group for each reference virus; the direction and size of any such differences cannot be established from the available registry results.

3. Trial Design

The registry describes NCT06054269, titled “Clinical Trial to Evaluate the Immunogenicity of an Adjuvanted Influenza Vaccine Among HCP.” Its official title identifies it as a randomized, controlled, double-blind, Phase III trial, and the registry classifies the allocation as randomized, the model as parallel, and masking as quadruple. The brief summary uses the term double-blinded, while the registry’s masking classification is quadruple; the identities of the masked groups are not reported in the registry record.

The planned comparison is between FLUAD Quadrivalent and FluQuadri. Both arm descriptions specify a single dose of an egg-based quadrivalent influenza vaccine and 15 µg of HA from each strain. FLUAD Quadrivalent is described as adjuvanted, while FluQuadri is described as standard dose. The trial summary places the work at two sites in Lima, Peru, during 2022 and 2023. The registry reports enrollment of 192, a start date of 2022-11-04, primary completion on 2023-07-25, and a completed status.

The stated primary endpoint is the HI geometric mean titer (GMT) after vaccination, measured at 28 days post-vaccination for each of four vaccine reference viruses. The registry lists six outcome measures and 24 analyses, but does not give the full set of outcome definitions or explain how the analyses map to the outcomes. It also does not report the allocation ratio, randomization procedure, concealment method, detailed eligibility criteria, or analysis population definitions. Those omissions limit how fully the implementation and analysis can be reconstructed from 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

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 Hemagglutination Inhibition (HI) Geometric Mean Titers (GMT) Post-vaccination (Day 28) of Each Vaccine Reference Virus, measured over 28 days post-vaccination.

The primary endpoint measures antibody titers after vaccination using the hemagglutination inhibition assay. The registry specifies geometric mean titers for egg-grown A(H1N1)pdm09, A(H3N2), B/Yamagata, and B/Victoria vaccine reference viruses, assessed at approximately 28 days post-vaccination. The reported statistical measure is a geometric least-squares mean with a 95% confidence interval.

HI assays quantify the extent to which antibodies inhibit a virus-related hemagglutination process. In general, antibody titers are used as a laboratory measure of humoral immune response; they are not themselves a direct count of clinical influenza cases. A geometric mean is used for titer data because such measurements are often analyzed on a logarithmic scale and summarized back on the original scale. A geometric least-squares mean typically reflects a model-based mean after such analysis, but the registry does not describe the model, any covariates, or the transformation used.

The endpoint is virus-specific, so the registry’s stated primary measure entails separate titers for the listed reference viruses rather than a single overall titer. The registry does not report the numerical estimates, confidence interval limits, or a prespecified threshold for interpreting a difference. Consequently, the endpoint definition identifies what was measured and when, but does not establish the magnitude, precision, or practical importance of the comparison.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The central statistical measure named for the primary endpoint is the geometric least-squares mean, abbreviated in the registry title as a geometric mean titer. The HI assay produces antibody titer measurements, and the registry says these are summarized for each virus at 28 days post-vaccination. A geometric mean is a way to summarize positive, often right-skewed measurements: the values are analyzed on a logarithmic scale and then expressed back on the original scale. In general, this can make a summary less dominated by very high values than an arithmetic mean would be. The registry record does not give the exact transformation, model, or estimation procedure used in this trial, so those details should not be assumed.

The term “least-squares mean” generally refers to a model-based estimate, sometimes adjusted for variables included in a statistical model. What variables, if any, were included in the model are not reported in the registry record. Nor is the specific group contrast described. The endpoint title gives the group-level GMT measure and its confidence interval format, but does not state whether the primary comparison was framed as a difference, ratio, or another contrast. The numerical group estimates and comparison results are not reported in the registry record.

A 95% confidence interval describes uncertainty around an estimated quantity under the assumptions of the analysis. In general, a narrower interval indicates greater precision, while a wider interval indicates less precision. The interval is not a guarantee that a particular value is correct, and it does not by itself establish clinical importance. For this trial, the registry specifies 95% confidence intervals but does not provide their endpoints. Precision and compatibility with different possible effects therefore cannot be assessed from the registry record.

The outcome is virus-specific. The registry describes measurements for egg-grown A(H1N1)pdm09, A(H3N2), B/Yamagata, and B/Victoria. Separate estimates can reflect responses to each reference virus, but multiple outcomes also raise questions about interpretation across analyses. The registry lists six outcome measures and 24 analyses, and says the primary outcome has several categories or time points and is not reduced to one comparison. The full outcome definitions, all corresponding estimates, and the method for handling multiple statistical tests are not reported in the registry record. General statistical practice may use a prespecified hierarchy or multiplicity adjustment to address multiple comparisons, but no such method can be attributed to this trial from the available record.

Randomization is intended, in general, to make treatment groups comparable on average at the start of a trial, supporting interpretation of between-group comparisons. The record identifies the allocation as randomized and the model as parallel, but does not report the randomization sequence generation, allocation concealment, or allocation ratio. The official title calls the trial double blind, while the registry classifies masking as quadruple; the identities of the masked parties and procedures for maintaining masking are not reported in the registry record. These details matter when assessing risk of bias and implementation.

The sample-size assumptions described for planning calculations are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The planning illustration is based on a stated fraction of the observed effect. Such a calculation is a design illustration: it does not measure the probability that the completed trial found a true effect, and it is not observed power. The numerical planning outputs and the trial’s own sample-size justification are not reported in the registry record. The stated enrollment of 192 is not, by itself, an explanation of how that target was selected.

Over-dispersion is a general concern when observed variability exceeds what a statistical model assumes. If unaccounted for, it can make uncertainty estimates too narrow and tests too optimistic; a suitable model may need to allow for the extra variability. The registry does not report whether over-dispersion was assessed or whether it was relevant to the endpoint analysis. Likewise, details about model diagnostics, covariate adjustment, sensitivity analyses, and handling of assay values outside measurable ranges are not reported in the registry record.

Finally, a statistical result needs both an estimate and its uncertainty to be interpretable. A p-value, if reported, would address compatibility with a specified null model under assumptions; it would not measure the probability that the null hypothesis is true or indicate whether an effect is important. The registry record does not report primary endpoint estimates, confidence interval limits, or p-values. Therefore, the methods that can be explained are limited to the named endpoint, interval format, and stated planning assumptions; the actual inferential analysis cannot be reconstructed in full.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures and 24 analyses. It also notes that the primary outcome has several categories or time points and is not reduced to one comparison. In this setting, multiplicity refers generally to the interpretive issue created by evaluating multiple outcomes, time points, categories, or statistical contrasts. The more comparisons considered, the more important it is to know which were designated as primary and whether any procedure was planned to control the overall chance of false-positive findings.

The registry record does not report a multiplicity adjustment, a hierarchy among endpoints, or a complete prespecified testing strategy. The four virus-specific measurements named for the primary endpoint are clear, but their relationship to the six listed outcome measures and 24 analyses is not fully described. Without that information, the statistical priority of individual results and the intended interpretation across all analyses cannot be established.

Missing-data handling is also not reported in the registry record. The enrollment figure is 192, but the record does not provide primary-endpoint analysis counts, the number of unavailable samples, reasons for missing measurements, or methods for addressing missing outcomes. It does not state whether all randomized participants were analyzed, whether a per-protocol population was used, or how participants with protocol deviations were handled. Those analysis-population definitions affect how the results should be understood and whether the groups remain comparable in the analysis.

In general, missing observations and multiple analyses can influence precision and interpretation. The direction and extent of any influence depend on the actual pattern of missingness and the methods used. Neither can be inferred from the registry record alone.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse event counts for each arm alongside the numbers at risk. In the FLUAD Quadrivalent group, 0 serious adverse events were recorded among 95 participants at risk. In the FluQuadri group, 0 serious adverse events were recorded among 97 participants at risk. Deaths are reported as 0 in each group. The registry lists no top serious-event terms.

For other adverse events, the record lists 70 among 95 participants at risk in the FLUAD Quadrivalent group and 61 among 97 in the FluQuadri group. These are counts, not a complete description of event types or severity. The record does not report the definitions used for serious and other adverse events, whether counts represent participants or individual events, the observation period for safety collection, or event-specific details. It also does not provide a statistical comparison of the groups.

Zero recorded serious events in these groups means none were listed in the registry results; it does not establish that serious events are impossible or that the groups have equivalent safety. The available counts support a descriptive reading only. They do not provide enough detail to assess differences in the type, timing, severity, or relationship of adverse events to vaccination.

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

The trial addresses a laboratory measure of humoral immune response after vaccination. Its primary endpoint is defined as HI geometric mean titers at 28 days post-vaccination for four vaccine reference viruses, with 95% confidence intervals. The registry also provides the broad comparison: a single dose of adjuvanted FLUAD Quadrivalent versus a single dose of standard-dose FluQuadri among health care personnel. These details establish what the study set out to measure and how the two arms were described.

The registry record does not report the numerical GMTs, confidence interval limits, or primary comparison results. It therefore does not show whether titers were higher in either group, how large any group difference was, or how precisely an estimate was determined. The endpoint description alone cannot be used to infer a result. In particular, it cannot establish that the vaccines produced identical or different responses.

Even if numerical antibody results were available, a laboratory titer is not the same outcome as clinical influenza illness. The record’s stated primary outcome concerns antibody titers; it does not identify a clinical illness endpoint as the primary measure. The registry summary describes an immunogenicity comparison and does not report a conclusion about prevention of influenza or other clinical outcomes. Statistical interpretation should remain tied to the outcomes actually specified.

The safety figures are also descriptive. The registry reports zero serious adverse events and zero deaths in both groups, as well as counts of other adverse events. Without event definitions, detailed event information, analysis methods, and a comparative estimate, those counts do not establish equivalence or prove a safety difference. The record does not provide a basis for medical advice or treatment decisions.

Accordingly, the record supports a description of trial design, outcome measurement, and the reported safety counts, but not a conclusion about the size or importance of the primary immunogenicity comparison. Numerical endpoint results and analysis details are needed for that assessment.

13. Why This Trial Matters Statistically

This trial is statistically relevant because it illustrates the distinction between defining an endpoint and reporting its result. The registry identifies a clear laboratory measurement, a post-vaccination time point, and virus-specific reference strains. It also specifies a geometric least-squares mean and a 95% confidence interval. Those elements tell readers what quantity was intended to summarize the antibody response, but they do not establish the observed group estimates or their precision.

The design also involves multiple virus-specific outcomes and a larger set of listed analyses. With multiple outcomes, readers need to know which comparisons were primary, how other analyses were classified, and whether any adjustment or hierarchy was prespecified. The registry lists six outcome measures and 24 analyses, but does not report the complete analysis plan or multiplicity strategy. That makes it difficult to interpret a collection of results as a whole, even if individual estimates were available.

Another statistical lesson concerns the distinction between enrollment and analysis. The registry reports enrollment of 192, while the safety summaries give numbers at risk by arm. The primary endpoint analysis counts and missing-sample handling are not reported. Enrollment alone does not indicate how much information contributed to each endpoint estimate, so analysis populations and missingness details are important for evaluating precision and possible bias.

Finally, the sample-size assumptions described for planning illustrate that design calculations depend on choices such as a significance level, allocation, and assumed effect. A planning illustration is not evidence that the completed study had a particular probability of detecting an effect, and it cannot replace the observed estimate and confidence interval. The absence of numerical primary results in the registry record makes this distinction especially important: a design description should not be mistaken for an empirical finding.

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 record leaves important details unavailable for a full statistical assessment. It gives a primary endpoint definition and interval format, but does not report the numerical endpoint estimates, confidence interval limits, or p-values. As a result, the primary comparison cannot be evaluated for direction, magnitude, or precision using the registry record.

The record does not describe the statistical model, transformation, covariate adjustment, or exact group contrast used for the geometric least-squares means. It also does not explain how the six outcome measures and 24 analyses relate to the primary endpoint or identify a multiplicity strategy. These omissions limit assessment of whether the reported analysis, if consulted elsewhere, matches a prespecified plan.

Details about randomization and masking are incomplete. The registry classifies the trial as randomized and quadruple-masked, while the brief summary calls it double-blinded. It does not explain which participants or study personnel were masked, how allocation was concealed, or how randomization was implemented. Eligibility criteria, analysis populations, protocol deviations, and the number of participants contributing primary endpoint data are also not reported in the registry record.

Missing-data methods and assay-specific handling are not described. The record does not state how unavailable titers, measurements outside assay limits, or incomplete follow-up were handled. For safety, adverse-event definitions, collection windows, event-level details, and statistical comparisons are not reported. These limitations do not show that the trial was conducted improperly; they mean the registry record alone does not contain enough information to assess these aspects.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Clinical Trial to Evaluate the Immunogenicity of an Adjuvanted Influenza Vaccine Among HCP — NCT06054269.
• Registry record last updated 2026-05-19; status last verified 2026-05.
• Results first posted 2025-05-29.
• 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

NCT06054269 is a completed, randomized, parallel-group Phase III trial comparing FLUAD Quadrivalent with FluQuadri among health care personnel. The registry reports enrollment of 192, with a start date of 2022-11-04 and primary completion on 2023-07-25. The trial summary places the study at two sites in Lima, Peru, during 2022 and 2023.

The primary endpoint is HI geometric mean titers for four vaccine reference viruses at 28 days post-vaccination, reported with 95% confidence intervals. The numerical primary results are not reported in the registry record. Safety summaries list zero serious adverse events and zero deaths in both groups, alongside counts of other adverse events. The registry does not report the full statistical plan, analysis populations, missing-data methods, or multiplicity strategy.