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 Collection of Serum Samples From Children and Older Adults Receiving the 2019-2020 Formulations of Fluzone® Quadrivalent and Fluzone® High-Dose Influenza Vaccines, Respectively (NCT04109222), a non-randomized phase 4 study. The primary outcome is Number of Participants Aged 6 Months to < 9 Years Who Provided Serum Samples for Analysis: Groups 1 and 2.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04109222 |
| Phase | Phase 4 |
| Condition | Influenza |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 90 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sanofi Pasteur, a Sanofi Company |
| Results posted | Yes |
2. Clinical Question
Population
The study involved children aged 6 months to < 9 years and adults aged ≥ 65 years. The registry describes two groups of children receiving Fluzone Quadrivalent and one group of older adults receiving Fluzone High-Dose. Enrollment was 90.
Intervention
Children received the 2019-2020 formulation of Fluzone Quadrivalent, described as a 0.5-mL dose given intramuscularly at Day 0. A second dose at Day 28 was given to participants for whom 2 influenza vaccine doses were recommended per ACIP. Adults aged ≥ 65 years received a 0.5-mL intramuscular dose of the 2019-2020 Fluzone High-Dose formulation at Day 0.
Comparator
The study was non-randomized and its groups were defined by age and vaccine formulation. The registry record does not describe a like-for-like control comparison. Differences between the groups therefore cannot be interpreted as randomized treatment contrasts.
Primary question
The primary objective was to collect serum before vaccination and after final vaccination, then make the samples available for further analysis by CBER, WHO, CDC, and FDA to support recommendations for subsequent influenza vaccine formulations. The primary outcome was the number of children aged 6 months to < 9 years who provided serum samples for analysis. The outcome count is not reported in the registry record.
3. Trial Design
NCT04109222 is listed as a completed Phase 4, non-randomized, parallel study of the 2019-2020 formulations of Fluzone Quadrivalent and Fluzone High-Dose. The registry lists influenza as the condition and Sanofi Pasteur, a Sanofi Company, as the sponsor. Enrollment was 90. The study started on 2019-09-30, and primary completion was recorded as 2019-12-10.
The three groups were organized by age and vaccine formulation. Children aged 6 to < 36 months and children described in the arm record as 3 to 9 years received Fluzone Quadrivalent. The group descriptions state that a second dose at Day 28 was given to participants for whom 2 doses were recommended per ACIP. Adults aged ≥ 65 years received Fluzone High-Dose at Day 0. The official title describes the child population as 6 months to < 9 years, while the second arm description says 3 to 9 years; the registry record does not explain this difference in wording.
Masking is listed as none, and allocation is listed as non-randomized. The parallel structure means that different groups received different formulations; it does not establish that the groups were exchangeable or intended as direct controls for one another. The primary objective was serum collection to support further analysis by external public-health and regulatory organizations. The registry does not describe a treatment-efficacy hypothesis, a randomized comparison, or a masking procedure. Further details about the operational protocol 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.
Before assignment: A total of 90 participants were enrolled and vaccinated in the study.
Overall Study
| Stage | Group 1: Fluzone Quadrivalent Influenza Vaccine: 6 to < 36 Months | Group 2: Fluzone Quadrivalent Influenza Vaccine: 3 to < 9 Years | Group 3: Fluzone High-Dose Influenza Vaccine: >= 65 Years |
|---|---|---|---|
| STARTED | 30 | 30 | 30 |
| COMPLETED | 29 | 30 | 30 |
| NOT COMPLETED | 1 | 0 | 0 |
Reasons for not completing this period:
| Reason | Group 1: Fluzone Quadrivalent Influenza Vaccine: 6 to < 36 Months | Group 2: Fluzone Quadrivalent Influenza Vaccine: 3 to < 9 Years | Group 3: Fluzone High-Dose Influenza Vaccine: >= 65 Years |
|---|---|---|---|
| Adverse Event | 1 | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Analysis was performed on all vaccinated participants i.e. the participants who have received at least 1 dose of the study vaccine. Here, 'Overall number of participants analyzed' = participants evaluable for this outcome measure.
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.
Population: Analysis was performed on all enrolled and vaccinated participants.
| Characteristic | Unit | Group 1: Fluzone Quadrivalent Influenza Vaccine: 6 to < 36 Months | Group 2: Fluzone Quadrivalent Influenza Vaccine: 3 to < 9 Years | Group 3: Fluzone High-Dose Influenza Vaccine: >= 65 Years | Total |
|---|---|---|---|---|---|
| Participants analysed | 30 | 30 | 30 | 90 | |
| Age, Categorical: <=18 years | Participants | 30 | 30 | 0 | 60 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 | 0 | 0 | 0 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 30 | 30 |
| Age, Continuous | years | 1.86 (SD 0.29) | 5.43 (SD 1.45) | 71.83 (SD 5.16) | 26.38 (SD 32.50) |
| Sex: Female, Male: Female | Participants | 18 | 13 | 16 | 47 |
| Sex: Female, Male: Male | Participants | 12 | 17 | 14 | 43 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 | 2 | 0 | 2 |
| Race (NIH/OMB): White | Participants | 29 | 25 | 30 | 84 |
| Race (NIH/OMB): More than one race | Participants | 1 | 3 | 0 | 4 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants Aged 6 Months to < 9 Years Who Provided Serum Samples for Analysis: Groups 1 and 2, measured over Visit 1 (Day 0; pre-vaccination) and 28 days post-final vaccination at Visit 2/Visit 3.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the number of children aged 6 months to < 9 years who provided serum samples for analysis. The samples were collected before the first vaccination at Visit 1 (Day 0) and after the final vaccination. For participants who received one dose, the post-vaccination sample was scheduled at Visit 2, 28 days after Visit 1. For participants who received two doses, it was scheduled at Visit 3, 28 days after Visit 2. The endpoint therefore concerns sample availability at the specified collection points, not a reported immune-response measurement.
This kind of count can describe how many participants met the sample-collection outcome, which is relevant when the study’s purpose is to assemble specimens for further laboratory analysis. A count alone does not describe antibody levels, protection, or a contrast between vaccine formulations. Those later analyses were identified as work for CBER, WHO, CDC, and FDA, but their results are not reported in the registry record.
The registry defines the analysis population as all vaccinated participants, meaning participants who received at least one dose, and describes the analyzed number as those evaluable for this outcome. The actual primary endpoint count is not reported in the registry record. Consequently, the extent to which the planned pre- and post-vaccination samples were obtained cannot be assessed from the posted outcome information.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the study’s purpose and structure, but it does not report the primary endpoint count. The endpoint is the number of children aged 6 months to < 9 years who provided serum samples for analysis at the specified pre-vaccination and post-final-vaccination visits. Without a reported count, the posted results do not show how many children met that sample-collection outcome or how many were evaluable.
The study enrolled 90 participants, and its groups were non-randomized and separated by age and vaccine formulation. These features matter when interpreting any apparent differences across groups. The child groups and the older-adult group are not described as comparable populations assigned to alternative treatments. A difference in outcomes between them would not, by itself, isolate a vaccine-formulation effect from differences in age, group membership, or other factors. The registry record supplies no randomized treatment contrast to support such an interpretation.
The primary objective was to make serum samples available for later analysis by CBER, WHO, CDC, and FDA, in support of recommendations for subsequent influenza vaccine formulations. This is distinct from reporting the results of those laboratory analyses. The posted primary outcome is a sample-provision count, not an immunogenicity result. No antibody measurements or other laboratory outcomes are described in the primary outcome information. Such results are not reported in the registry record.
The registry lists 0 analyses. It does not provide an effect estimate, confidence interval, or p-value for the primary outcome. A confidence interval, in general, communicates the precision of an estimated quantity; without an estimate and interval, readers cannot assess statistical uncertainty around the sample-collection result. Nor can the record support a claim about differences between vaccine formulations or the degree to which the serum samples informed later recommendations.
The safety record reports serious adverse events affecting 1 participant in Group 1 and 0 participants in each of Groups 2 and 3. It records 0 deaths in all three groups. These figures are descriptive and should be read in light of the group structure and the absence of a randomized comparator. They do not establish that an event was caused by a vaccine, nor do zero reported events in a group prove that an event cannot occur.
Overall, the posted information documents a completed serum-collection study and its intended contribution to later vaccine formulation work. It does not report the primary count or the downstream laboratory findings. Interpretation should therefore remain focused on the study’s documented purpose, design, and reported safety counts, rather than conclusions about comparative vaccine effects.
9. Statistical Methods Explained
The registry characterizes the primary outcome as a participant count. The measure asks how many children in the stated age range provided serum samples for analysis. For a count outcome, the direct descriptive result would be the number of participants meeting the outcome, interpreted in relation to the participants evaluable for it. The registry provides the outcome definition and population description, but not the actual count. It also lists 0 analyses, so no inferential result for this endpoint is reported.
What does a count endpoint tell readers?
A count can describe the frequency of an event or outcome in a defined group. In this study, the event of interest is provision of serum samples at the required collection times. The endpoint is not itself a laboratory measurement. A count would describe sample collection, but would not indicate the samples’ antibody content or the results of any subsequent testing. Those distinctions are important because the stated study objective was to collect specimens for further analysis by CBER, WHO, CDC, and FDA.
Counts can be presented with a denominator to clarify how many participants were eligible or evaluable. The registry defines the analysis population as all vaccinated participants, meaning those who received at least one dose, and says the overall number analyzed equals participants evaluable for the outcome. However, the number evaluable and the number meeting the endpoint are not reported in the registry record. Readers therefore cannot assess the endpoint count or its completeness from the posted result information.
Why does the design affect comparisons?
Allocation is listed as non-randomized, masking as none, and the model as parallel. In general, random allocation helps balance both measured and unmeasured participant characteristics across treatment groups. Without randomization, observed group differences can reflect baseline differences as well as treatment or formulation. In this study, the groups also differ in age range and formulation, so they are not described as a like-for-like control comparison. The registry record does not report an adjusted analysis intended to address such differences.
Masking concerns whether participants or study personnel know which intervention is assigned. The registry lists no masking. In a study whose stated primary purpose is serum collection, this design detail does not turn the endpoint into a comparative treatment outcome. It remains necessary to distinguish the documented specimen-collection objective from downstream laboratory analyses, which are not reported in the registry record.
What does statistical uncertainty mean in general?
General statistical interpretation often uses an estimate together with a confidence interval. An estimate gives a central value, while the interval expresses how much uncertainty is compatible with the data and the method used. A narrower interval generally indicates greater precision than a wider interval, but precision also depends on the target quantity and assumptions. No confidence interval or primary endpoint estimate is reported in the registry record, so the precision of the sample-collection outcome cannot be evaluated.
A p-value, when reported, addresses compatibility between observed data and a specified statistical model under a null hypothesis. It does not measure the probability that a treatment works, and it does not express the size or importance of an effect. The registry lists 0 analyses and reports no p-value for the primary endpoint. No hypothesis test can therefore be interpreted from the posted results.
How should planning illustrations be understood?
Sample-size planning uses assumptions about a target effect, variability, allocation, significance level, and desired power to illustrate the amount of information a future comparison might require. The registry’s planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of an observed effect. These are planning illustrations, not an account of the study’s own design justification or observed power. The registry record does not report a sample-size justification for this trial.
In general, power is the probability that a specified study design will detect a particular effect if that effect is present, given the assumptions used. A planning calculation is conditional on those assumptions; it is not evidence that a completed study had a particular probability of success. An observed result should not be described as having a post hoc observed power. The planning assumptions also describe a two-arm comparison, whereas this study is non-randomized and includes groups differentiated by age and vaccine formulation. Any planning illustration should therefore not be mistaken for a randomized comparison conducted in this study.
For count outcomes, interpretation may also depend on the distribution and modeling assumptions. General count-data methods can account for variation that exceeds what a simple model expects, a feature often called over-dispersion. Over-dispersion matters because a model that understates variability can produce confidence intervals that are too narrow and tests that appear more decisive than warranted. The registry record does not report a count model, a dispersion assessment, or an inferential analysis for the primary endpoint, so there is no basis to say that a particular method was used.
The registry provides no model specification, covariate adjustment, or variance estimate for the primary outcome. These omissions prevent a reader from reconstructing an inferential analysis, even if the endpoint count were available. The most defensible statistical reading is descriptive: the registry defines what was intended to be counted, identifies the vaccinated and evaluable population, and leaves the observed endpoint result and its uncertainty unreported.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 2 outcome measures, but the details reported for the primary endpoint concern the number of children aged 6 months to < 9 years who provided serum samples. The details of any additional outcome measure are not reported in the registry record. A multiplicity strategy—such as adjustment of significance thresholds or a hierarchy specifying which outcomes were confirmatory—is also not reported. Because the record lists 0 analyses and no primary endpoint estimate or p-value, there is no reported testing family to evaluate.
Missing-data handling is not reported in the registry record. The primary outcome description explains the intended pre-vaccination and post-final-vaccination collection visits, but does not state how incomplete collections, missed visits, or unevaluable samples were handled. The analysis population is described as all vaccinated participants who received at least one dose, with the overall number analyzed defined as participants evaluable for the outcome. The number vaccinated and the number evaluable are not reported for the primary endpoint, so the extent of any missing outcome data cannot be assessed.
The registry record does not report an intention-to-treat analysis, a per-protocol analysis, imputation, sensitivity analyses, or reasons for missing samples. These methods should not be assumed. A sample-collection outcome can be affected by whether participants contribute samples at both required time points; without the outcome counts and missing-data rules, readers cannot determine how complete the planned collection was or whether the analyzed participants differed from those not evaluable.
Interim analyses and a statistical plan are not reported in the registry record. That absence means the posted information does not establish whether interim looks were planned or conducted, or how the study would have handled multiple analyses. It does not establish that such procedures did or did not occur outside the registry description.
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 |
|---|---|---|---|
| Group 1: Fluzone Quadrivalent Influenza Vaccine: 6 to < 36 Months | 1 | 30 | 3.3% |
| Group 2: Fluzone Quadrivalent Influenza Vaccine: 3 to < 9 Years | 0 | 30 | 0.0% |
| Group 3: Fluzone High-Dose Influenza Vaccine: >= 65 Years | 0 | 30 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Group 1: Fluzone Quadrivalent Influenza Vaccine: 6 to < 36 Months | 0 of 30 |
| Group 2: Fluzone Quadrivalent Influenza Vaccine: 3 to < 9 Years | 0 of 30 |
| Group 3: Fluzone High-Dose Influenza Vaccine: >= 65 Years | 0 of 30 |
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 |
|---|---|
| Group 1: Fluzone Quadrivalent Influenza Vaccine: 6 to < 36 Months | 0 of 0 |
| Group 2: Fluzone Quadrivalent Influenza Vaccine: 3 to < 9 Years | 0 of 0 |
| Group 3: Fluzone High-Dose Influenza Vaccine: >= 65 Years | 0 of 0 |
Most frequent serious adverse event terms
| Event term | Organ system | Group 1: Fluzone Quadrivalent Influenza Vaccine: 6 to < 36 Months | Group 2: Fluzone Quadrivalent Influenza Vaccine: 3 to < 9 Years | Group 3: Fluzone High-Dose Influenza Vaccine: >= 65 Years |
|---|---|---|---|---|
| Parainfluenzae virus infection | Infections and infestations | 1 of 30 | 0 of 30 | 0 of 30 |
Serious events with the highest arm-level rate: parainfluenzae virus infection (3.3%).
The registry reports serious adverse event counts for each group. In Group 1, 1 of 30 participants at risk was reported as affected. In Group 2, 0 of 30 were reported as affected, and in Group 3, 0 of 30 were reported as affected. The registry lists 0 deaths in each group. The group descriptions identify Group 1 and Group 2 as children receiving Fluzone Quadrivalent, and Group 3 as adults aged ≥ 65 years receiving Fluzone High-Dose.
The serious-event term listed among the top terms is Parainfluenzae virus infection, at 3.3%. The registry information does not establish from that listing which group the term belongs to or whether it is the event recorded for the participant in Group 1. The term and percentage should therefore be read as a registry listing, not as a group-specific comparison.
These are descriptive safety counts, not estimates of causal risk. The study is non-randomized and the groups differ by age and formulation. Zero reported serious adverse events or deaths in a group does not establish that the risk is absent. Conversely, a reported event does not by itself show that vaccination caused it. The registry record does not report a comparative safety analysis or an adjusted estimate.
12. What the Result Does, and Does Not, Mean
The record supports a limited conclusion about study purpose: serum was intended to be collected before vaccination and after final vaccination from children and older adults receiving the specified 2019-2020 formulations. The stated goal was to make those samples available for further analysis by CBER, WHO, CDC, and FDA, to support recommendations for subsequent influenza vaccine formulations. The study is listed as completed.
The record does not report the primary endpoint count. It therefore does not establish how many children provided samples at the required collection times, how many were evaluable, or how complete the collection was. It also does not report the findings of subsequent analyses of the serum. A specimen-collection objective and the results of laboratory testing are different kinds of evidence; the former does not reveal the latter.
This study should not be read as a randomized comparison between the two vaccine formulations. Allocation was non-randomized, masking was none, and the groups were organized by age and formulation. The record does not describe an equivalent control group or a comparative treatment-effect analysis. Consequently, it does not support a causal claim that one formulation performed better or worse than another.
The safety figures describe serious adverse events reported in the groups and list no deaths. They do not provide a randomized or adjusted comparison, and they do not prove that an event was caused by a vaccine or that no risk exists where no event was recorded. Interpretation of safety is further limited because the posted record does not include a comparative analysis.
In general, a result’s meaning depends on the outcome measured, who was analyzed, how the groups were formed, and how uncertain the estimate is. Here, the endpoint definition and population description are available, but the observed primary result, its statistical precision, and the downstream serological findings are not reported in the registry record. The meaning is therefore primarily methodological: this was a serum-collection study intended to support later external analyses, not a posted report of vaccine effectiveness or comparative immunogenicity.
13. Why This Trial Matters Statistically
Serum-collection studies can contribute to the evidence used in later formulation work by making biological samples available for specialized analysis. This study’s stated objective was to collect samples from children and older adults receiving the relevant seasonal formulations and make them available to CBER, WHO, CDC, and FDA. That objective explains why a sample-collection count was chosen as the primary endpoint rather than a comparative clinical outcome.
Statistically, the distinction between collecting specimens and analyzing them is important. The primary endpoint concerns whether participants provided samples at defined visits. It does not report antibody measurements or other laboratory findings. Those later analyses could address different scientific questions, but their results are not reported in the registry record. Keeping these stages separate prevents a sample-collection record from being mistaken for an immunogenicity or effectiveness result.
The design also illustrates why group labels do not automatically imply a valid treatment comparison. The study was non-randomized, and the groups differed in age and vaccine formulation. A comparison across such groups would be vulnerable to differences associated with age and group composition, apart from any vaccine-related difference. The registry does not report a comparative model or analysis that resolves those issues.
Finally, transparent outcome reporting is central to assessing whether an intended collection was achieved. The registry defines the endpoint and analysis population but does not report the endpoint count or evaluable sample size. Without those results, readers cannot judge collection completeness or precision. The record’s value is its documentation of the study objective, group structure, and reported safety counts, while its limits show why counts, denominators, analysis methods, and downstream laboratory results all matter for statistical interpretation.
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 of the posted results is that the primary outcome count is not reported in the registry record. The registry describes the number of children who provided serum samples as the primary endpoint, but does not report how many met that outcome or how many were evaluable. This prevents assessment of the collection outcome itself, including its completeness and precision.
The registry record also does not report the serum-analysis results that the collection was intended to support. No antibody measurements or findings from CBER, WHO, CDC, or FDA are described in the primary outcome information. The record therefore cannot answer questions about immune response or comparative vaccine performance.
The non-randomized, unmasked, parallel design is a further limitation for comparisons. Groups were distinguished by both age and formulation, and the registry explicitly does not describe them as a like-for-like control comparison. No adjusted comparative analysis is reported. The age description for the second child group is also inconsistent across registry text: the official title describes children up to < 9 years, while the arm description says 3 to 9 years. The registry record does not explain the difference.
Details needed to evaluate statistical methods are also absent. The registry record does not report the primary endpoint estimate, confidence interval, p-value, statistical model, missing-data procedure, multiplicity plan, or interim analyses. It does not report a sample-size justification. These omissions do not prove that a procedure was not used outside the registry record, but they mean that it cannot be assessed from the posted information.
Safety reporting is descriptive and does not establish causality. The listed serious adverse event term is not linked to a particular group in the available description, and no comparative safety analysis is reported. These limitations constrain conclusions to the documented design, objectives, and reported safety counts.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Collection of Serum Samples From Children and Older Adults Receiving the 2019-2020 Formulations of Fluzone® Quadrivalent and Fluzone® High-Dose Influenza Vaccines, Respectively — NCT04109222.
- Registry record last updated 2025-09-12; status last verified 2025-09.
- Results first posted 2020-12-17.
- 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
NCT04109222 is a completed, non-randomized, parallel Phase 4 study sponsored by Sanofi Pasteur, a Sanofi Company. Enrollment was 90. The study collected or planned to collect serum before vaccination and after final vaccination from children receiving Fluzone Quadrivalent and adults aged ≥ 65 years receiving Fluzone High-Dose, both in 2019-2020 formulations. The stated purpose was to make samples available to CBER, WHO, CDC, and FDA for further analysis supporting recommendations for subsequent influenza vaccines.
The primary endpoint was the number of children aged 6 months to < 9 years who provided samples for analysis. Its observed count, the number evaluable, and inferential analyses are not reported in the registry record. Serious adverse events were reported in 1 participant in Group 1 and 0 participants in Groups 2 and 3; 0 deaths were recorded in each group. These results document the study’s sample-collection purpose and selected safety counts, but do not report comparative vaccine effects or downstream serum-analysis findings.