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 Peds Sanofi H1N1 Influenza Vaccine Administered at Two Dose Levels (NCT00944073), a randomized phase 2 study. The primary outcome is Number of Participants Reporting Solicited Subjective Local Reactions After the First Vaccination.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00944073 |
| Phase | Phase 2 |
| Condition | Influenza |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 583 |
| Arms in the primary outcome | n/a |
| Lead sponsor | National Institute of Allergy and Infectious Diseases (NIAID) |
| Results posted | Yes |
2. Clinical Question
Population
Healthy volunteers in the age groups 6 months to less than 36 months, 36 months to 9 years, and 10 to 17 years were eligible. The brief summary describes participants as having no history of 2009 H1N1 influenza infection or vaccination. The registry record reports enrollment of 583 participants.
Intervention
Participants assigned to the 30 mcg group received inactivated H1N1 vaccine on Day 0 and Day 21. The vaccine was an unadjuvanted Sanofi Pasteur H1N1 vaccine.
Comparator
The comparator was the 15 mcg dose of the same vaccine, administered on Day 0 and Day 21. Assignment to the two dose groups was randomized.
Primary question
The primary endpoint was the number of participants reporting solicited subjective local reactions after the first vaccination, during Day 0-7. The registry record identifies pain, tenderness, and swelling as the local reactions and counts a participant if any symptom at any severity was reported on any of those days. It does not report the endpoint results by dose group.
3. Trial Design
This was a randomized, quadruple-masked, parallel-group Phase II study of an unadjuvanted H1N1 influenza vaccine. The registry record lists Influenza as the condition and the National Institute of Allergy and Infectious Diseases as the sponsor. The study is marked completed, with a start date of 2009-08 and a primary completion date of 2010-04.
Participants were assigned to receive either 15 mcg or 30 mcg of inactivated H1N1 vaccine. Both groups were scheduled to receive injections on Day 0 and Day 21. The arm descriptions state that 300 subjects were to receive each dose level. The brief summary describes enrollment of up to 650 healthy volunteers, while the registry record reports total enrollment of 583; the record does not explain the relationship between these figures or give the number assigned to each group.
The age groups were 6 months to less than 36 months, 36 months to 9 years, and 10 to 17 years. Study procedures listed in the brief summary included medical history, physical examination, a memory aid for recording symptoms, and blood collection. Participants were expected to be involved in study procedures for approximately 7 months.
The primary endpoint focused on solicited local reactions after the first vaccination. Secondary outcomes listed HAI antibody responses, including whether titers reached 1:40 or greater and whether titers increased four-fold or greater, with assessments after the second dose at specified time points. The registry record lists 37 outcome measures overall. It does not report the randomization method, allocation concealment procedures, or a detailed protocol for the masking process.
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 | 15 mcg H1N1 Vaccine | 30 mcg H1N1 Vaccine |
|---|---|---|
| STARTED | 292 | 291 |
| COMPLETED | 287 | 287 |
| NOT COMPLETED | 5 | 4 |
Analysis population for the primary outcome, as defined in the registry: All participants receiving the first vaccination are included in the safety cohort. Analyses are as treated.
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 | 15 mcg H1N1 Vaccine | 30 mcg H1N1 Vaccine | Total |
|---|---|---|---|---|
| Participants analysed | 292 | 291 | 583 | |
| Age, Categorical: <=18 years | Participants | 292 | 291 | 583 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 | 0 | 0 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Age, Continuous | years | 7.6 (SD 5.5) | 7.3 (SD 5.2) | 7.5 (SD 5.3) |
| Sex: Female, Male: Female | Participants | 129 | 137 | 266 |
| Sex: Female, Male: Male | Participants | 163 | 154 | 317 |
| Region of Enrollment: United States | participants | 292 | 291 | 583 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants Reporting Solicited Subjective Local Reactions After the First Vaccination, measured over Day 0-7 after first vaccination.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint counts participants who reported solicited subjective local reactions during Day 0-7 after the first vaccination. The reactions named in the endpoint description are pain, tenderness, and swelling. A participant is counted if any of these symptoms was reported at any severity on any of the eight days in the assessment period. The safety population is defined as all participants who received the first vaccination, and the analysis is described as treated.
A participant count is a straightforward way to describe how many people experienced at least one of the specified reactions under this definition. It differs from a measure of symptom intensity or duration: the endpoint does not distinguish severity levels in the count, and it does not count each report as a separate event. The registry record does not specify how the separate reaction types were to be combined for reporting by dose group, beyond its participant-count definition.
Solicited symptoms are collected because asking about specific reactions over a defined period can capture events that may not otherwise be volunteered or recorded as general adverse events. That is a general rationale for solicited safety outcomes, not a conclusion about the results of this trial. The registry record names this endpoint but does not report the numbers of participants with reactions in either group, uncertainty estimates, or a statistical comparison. Consequently, the posted record does not establish the observed frequency of this primary endpoint at either dose level.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a primary safety outcome but does not give its results. It therefore does not support a numerical comparison of local reactions between the 15 mcg and 30 mcg groups. In particular, no group-specific count for pain, tenderness, or swelling after the first vaccination is reported, and no estimate of the difference between dose groups is available. The absence of those results is distinct from finding no reactions or finding equal reaction frequencies.
The record does include adverse-event counts. For serious adverse events, 3 participants were affected among 292 at risk in the 15 mcg group, and 4 were affected among 291 at risk in the 30 mcg group. For other adverse events, the recorded figures are 253 among 292 at risk and 255 among 291 at risk, respectively. These are counts from the registry record; they do not supply a dose-group effect estimate or its precision. The record also lists serious adverse-event terms at 0.3% each: Bronchiolitis, Apnoea, Lower limb fracture, Cholecystitis, Cleft palate, and Asthma. Deaths are not reported in the registry record.
These safety figures should be read as descriptive counts rather than as evidence that one dose level caused more or fewer events. A comparison requires attention to the event definitions, populations included, follow-up, and uncertainty around the estimates. The registry record does not provide enough detail to assess those elements fully, and it does not report a statistical analysis of the counts.
The study also listed HAI antibody outcomes by age group and assessment time. Those endpoints describe planned measures of immune response, but their numerical results are not reported in the registry record. The endpoint titles alone cannot show how many participants met the antibody thresholds or how results varied by dose. Overall, the posted record describes study design and selected adverse-event counts, but it does not provide the primary endpoint results or the immunogenicity results needed for a complete account of the trial findings.
9. Statistical Methods Explained
The design is described as randomized and parallel-group. Randomization is intended, in general, to make the assigned groups comparable with respect to both measured and unmeasured characteristics, although chance differences can remain. A parallel-group design means each participant is assigned to a dose group rather than crossing between dose levels. The registry record does not describe the random sequence generation or allocation concealment procedures, so those aspects cannot be evaluated from the record.
What does the primary endpoint count?
The endpoint is a binary participant-level outcome: a participant either meets the endpoint definition or does not. The registry record defines meeting the endpoint as reporting pain, tenderness, or swelling at any severity on any day from Day 0-7 after the first vaccination. The stated population is all participants receiving the first vaccination, with analyses as treated. This definition focuses on whether a participant reported a symptom at least once during the specified period, rather than on the number of reports, how long a symptom lasted, or its intensity.
For a binary outcome, a common descriptive summary is the number of participants meeting the definition in each group, alongside the number assessed. A comparison may then be expressed using an effect measure such as a difference in event proportions, with a confidence interval to describe uncertainty. These are general statistical options; the registry record does not report which comparison measure or inferential procedure was planned or used for the primary endpoint. Nor does it give primary endpoint counts or confidence intervals.
How should uncertainty be understood?
In general, a confidence interval describes the range of effect values reasonably compatible with the observed data under the assumptions of the statistical method. A narrow interval indicates greater precision than a wide interval, while an interval spanning values on both sides of no difference may leave the direction or size of an effect uncertain. These concepts do not supply missing trial results. Since the registry record does not report a primary endpoint estimate or interval, the precision of a dose-group comparison cannot be assessed.
The registry record marks the study as quadruple-masked, but does not explain which people were masked or how masking was maintained. Masking can, in general, reduce the influence of expectations on reporting, assessment, or other study procedures. Solicited symptoms were recorded by participants or their parents or guardians using a memory aid, according to the endpoint description. The record does not describe how missing diary entries or incomplete symptom records were handled.
What do the planning assumptions mean?
The registry record includes a sample-size planning note describing an illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. The note distinguishes participants per arm for non-time-to-event outcomes from total events for time-to-event outcomes. No numerical planning outputs are reported in the registry record, and this illustration is not the trial's original design justification. The original sample-size justification is not reported in the registry record.
Such planning illustrations are hypothetical calculations about the sample size associated with stated assumptions. They are not observed power, and they do not replace an estimate of the treatment effect or its uncertainty. Because this trial's primary outcome has several categories or time points, the primary outcome was not reduced to one comparison in the available summary. The posted information therefore does not support a single primary-outcome effect estimate or a corresponding planning illustration tied to that estimate.
What analyses are documented?
The record lists outcome measures, including safety and immunogenicity outcomes, but does not include analysis records. It does not report a statistical analysis plan, the inferential tests used, covariate adjustment, subgroup analysis procedures, interim analyses, or how multiplicity was addressed. These omissions mean that readers cannot determine from the registry record whether analyses followed prespecified methods or whether any post hoc choices were made. The descriptive adverse-event counts remain useful as recorded, but they do not fill in those missing methodological details.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists 37 outcome measures, including the primary local-reaction endpoint and multiple HAI antibody outcomes across age groups and assessment times. Considering many endpoints or subgroups can increase the chance of observing an apparently notable result by chance if each is tested separately. General approaches to multiplicity include defining a hierarchy of outcomes, adjusting significance thresholds, or treating results as exploratory. The registry record does not report whether any such approach was planned or used.
The primary outcome has several categories or time points and was not reduced to one comparison in the available summary. The registry record does not provide the analysis plan needed to establish which comparisons were primary, how reaction categories were handled, or how conclusions across the outcomes were intended to be drawn. It also does not report interim analyses.
Missing-data handling is not described. The endpoint definition specifies a safety cohort of participants who received the first vaccination and an as-treated analysis, but the record does not say how participants with incomplete memory aids, missing assessments, or other unavailable observations were treated. It likewise does not report a missing-data sensitivity analysis. The registry record does not provide enough information to determine whether missingness differed by dose group or might have affected the estimates.
These are limitations in what can be assessed from the registry record, not evidence that the trial did or did not use particular procedures. Analysis populations beyond the stated safety cohort, and the handling of data for the listed immunogenicity outcomes, are not reported in 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 |
|---|---|---|---|
| 15 mcg H1N1 Vaccine | 3 | 292 | 1.0% |
| 30 mcg H1N1 Vaccine | 4 | 291 | 1.4% |
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 |
|---|---|
| 15 mcg H1N1 Vaccine | 253 of 292 |
| 30 mcg H1N1 Vaccine | 255 of 291 |
Most frequent serious adverse event terms
| Event term | Organ system | 15 mcg H1N1 Vaccine | 30 mcg H1N1 Vaccine |
|---|---|---|---|
| Cleft palate | Congenital, familial and genetic disorders | 1 of 292 | 0 of 291 |
| Asthma | Respiratory, thoracic and mediastinal disorders | 1 of 292 | 0 of 291 |
| Gastroenteritis | Infections and infestations | 1 of 292 | 0 of 291 |
| Bronchiolitis | Infections and infestations | 0 of 292 | 1 of 291 |
| Apnoea | Respiratory, thoracic and mediastinal disorders | 0 of 292 | 1 of 291 |
| Lower limb fracture | Injury, poisoning and procedural complications | 0 of 292 | 1 of 291 |
| Cholecystitis | Hepatobiliary disorders | 0 of 292 | 1 of 291 |
Most frequent non-serious adverse event terms
| Event term | Organ system | 15 mcg H1N1 Vaccine | 30 mcg H1N1 Vaccine |
|---|---|---|---|
| Tenderness | General disorders | 135 of 292 | 141 of 291 |
| Injection site pain | General disorders | 101 of 292 | 108 of 291 |
| Injection site erythema | General disorders | 89 of 292 | 91 of 291 |
| Headache | Nervous system disorders | 52 of 198 | 53 of 193 |
| Irritability | General disorders | 48 of 94 | 55 of 98 |
| Injection site swelling (functional grading) | General disorders | 54 of 292 | 48 of 291 |
| Injection site swelling (measured) | General disorders | 50 of 292 | 46 of 291 |
| Decreased activity | General disorders | 32 of 198 | 39 of 193 |
| Upper respiratory tract infection | Infections and infestations | 27 of 292 | 34 of 291 |
| Nausea | Gastrointestinal disorders | 25 of 198 | 33 of 198 |
Serious events with the highest arm-level rate: bronchiolitis (0.3%), apnoea (0.3%), lower limb fracture (0.3%), cholecystitis (0.3%), cleft palate (0.3%).
The serious adverse-event figures are counts of affected participants and participants at risk, as recorded by dose group. In the 15 mcg group, 3 participants were affected among 292 at risk; in the 30 mcg group, 4 were affected among 291 at risk. The separate figures for other adverse events are 253 among 292 at risk and 255 among 291 at risk. These categories should not be conflated: the registry record reports serious adverse events separately from other adverse events.
The listed serious adverse-event terms—Bronchiolitis, Apnoea, Lower limb fracture, Cholecystitis, Cleft palate, and Asthma—are each accompanied by 0.3%. The record does not provide further detail in the information available about the number of occurrences for each term, event timing, relatedness assessments, or whether an individual participant had more than one listed event. The listed percentage should therefore be read as the registry's reported figure for each term, not as a basis for a broader risk estimate.
Counts alone do not establish that an event was caused by vaccination or that the dose groups differ. The registry record does not report a comparative statistical analysis of these safety figures. Deaths are not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The trial record establishes that a randomized, quadruple-masked Phase II study compared 15 mcg and 30 mcg doses of an unadjuvanted H1N1 vaccine in pediatric age groups. It also specifies a primary safety endpoint based on solicited local reactions after the first vaccination and lists secondary HAI antibody outcomes. Those details describe the question and the measurements, but they are not themselves outcome findings.
The primary endpoint results are not reported in the registry record. The listed immunogenicity outcomes likewise do not include numerical results in the record available for this analysis. The adverse-event counts offer limited descriptive safety information, but there is no reported comparative estimate, confidence interval, or statistical test with which to assess the size and precision of a difference between dose groups. Thus the posted data do not establish whether local-reaction frequency or antibody response differed by dose.
Absence of reported primary or immunogenicity results should not be interpreted as evidence of no effect, no events, or equivalent outcomes. It means the registry record does not provide the numerical findings needed to answer those questions. Similarly, the serious adverse-event counts do not establish causation or a difference between dose groups.
In general, interpretation of a clinical trial requires both the design and the observed results, along with definitions, analysis methods, and uncertainty estimates. Here, key details about the statistical analysis, missing data, and multiplicity are not reported in the registry record. The conclusions that can be drawn are therefore limited to describing the study design, endpoint definitions, and recorded adverse-event figures—not determining the comparative safety or immune response of the dose levels.
13. Why This Trial Matters Statistically
This trial illustrates why a registry record's outcome definitions and outcome results need to be distinguished. The primary endpoint is described with a specific symptom set, assessment period, severity rule, and safety population. Those details make clear what the endpoint was intended to count. But without the group-specific counts or an effect estimate, readers cannot assess the observed frequency or compare dose levels for that endpoint.
The study also included several immunogenicity measures organized by age group and assessment time. Such outcome structures can raise questions about which comparisons carry the main inferential emphasis and how multiple comparisons are handled. The registry record lists the measures but does not report a statistical analysis plan or a multiplicity strategy. This prevents readers from assessing how the different outcomes were intended to support interpretation.
The adverse-event counts show another important statistical distinction: a count is descriptive information, whereas a comparative estimate with uncertainty is needed to assess how compatible the data are with different possible dose-group effects. The posted record includes some counts but not the analysis or uncertainty needed for a full comparison. Its serious adverse-event terms also illustrate why event labels and percentages need context about definitions, timing, and assessment.
Finally, a sample-size planning illustration should not be mistaken for a trial result or observed power. The registry note describes assumptions for an illustration, but the numerical planning outputs and original design justification are not reported in the registry record. This trial is therefore a useful example of how registration details can identify design intent while leaving important questions about results and analysis unresolved.
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 most consequential limitation for interpretation is that the registry record does not report the primary endpoint counts or a dose-group comparison. It also does not report numerical results for the listed HAI antibody outcomes. This prevents assessment of the trial's principal safety question and its stated immune-response outcomes from the information recorded.
The record reports total enrollment of 583 and planned arm descriptions of 300 subjects per dose group, but does not give the number actually assigned to or analyzed in each group for the primary endpoint. It identifies the safety cohort as participants receiving the first vaccination and says analyses are as treated, but does not specify the denominators used for the primary outcome results because those results are absent.
Important statistical details are not reported in the registry record, including the original sample-size justification, the statistical analysis plan, the multiplicity strategy, interim analyses, and handling of missing observations. The record also does not give the randomization method, allocation concealment procedures, or details about who was masked. These gaps limit assessment of the planned analysis and potential sources of bias.
For adverse events, the available counts do not include a comparative analysis or uncertainty estimates. Details about timing, relatedness, and the listed serious-event terms are not available in the record. The information also does not support conclusions about whether reported events were caused by vaccination. These limitations are specific to what the registry record reports and should not be mistaken for proof that the underlying study did not collect or analyze additional information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Peds Sanofi H1N1 Influenza Vaccine Administered at Two Dose Levels — NCT00944073.
- Registry record last updated 2015-02-18; status last verified 2010-03.
- Results first posted 2011-04-13.
- 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
NCT00944073 is a completed randomized, quadruple-masked, parallel-group Phase II study sponsored by the National Institute of Allergy and Infectious Diseases. It compared 15 mcg and 30 mcg doses of an unadjuvanted H1N1 influenza vaccine in age groups from 6 months through 17 years. The registry record reports enrollment of 583 participants and scheduled vaccinations on Day 0 and Day 21.
The primary endpoint counted participants reporting pain, tenderness, or swelling at any severity during Day 0-7 after the first vaccination. The registry record does not report results for this endpoint or numerical findings for the listed immunogenicity outcomes. It reports serious adverse-event counts of 3 among 292 at risk in the 15 mcg group and 4 among 291 at risk in the 30 mcg group, as well as other adverse-event counts. A statistical analysis plan, missing-data approach, and multiplicity strategy are not reported in the registry record.