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 Study of Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis Vaccine (ADACEL®) as a Booster in Adolescents (NCT01689324), a na phase 1, phase 2 study. The primary outcome is Percentage of Participants With Seroprotection Against Diphtheria and Tetanus Antigens Following Vaccination With ADACEL®.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01689324 |
| Phase | Phase 1, Phase 2 |
| Condition | Pertussis, Tetanus, Diphtheria |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 43 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sanofi Pasteur, a Sanofi Company |
| Results posted | Yes |
2. Clinical Question
Population
Japanese adolescents enrolled in a study of a booster dose of ADACEL®. The registry record reports enrollment of 43 participants. It identifies the Immunology Analysis Set for determining seroprotection, but does not report its size or further eligibility details.
Intervention
A single booster dose of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine, ADACEL® (SP306), administered on Day 0. The study was intended to assess immunogenicity and safety after vaccination.
Comparator
There was no separate comparator group. The study is recorded as a single-group study, with allocation listed as not applicable. Thus, the registry record does not describe a randomized or like-for-like comparison with another vaccine or with no booster.
Primary question
At Day 28 post-vaccination, what percentage of participants had antibody concentrations of at least 0.1 IU/mL for diphtheria and tetanus antigens? The registry record names this as the primary endpoint but does not report its results.
The study’s stated primary objective was to assess immunogenicity after a single Tdap dose in Japanese adolescents. Its secondary objective was to assess safety. These are distinct questions: the primary endpoint concerns antibody concentrations meeting a defined threshold, while safety reporting concerns adverse events. The record describes the questions and the endpoint definition, but not the measured antibody results. It therefore does not establish what percentage met the threshold, how precisely that percentage was estimated, or whether the registry’s wording refers to separate antigen-specific results or a combined criterion.
3. Trial Design
This was a completed, single-group study of ADACEL® as a booster in Japanese adolescents. The registry records the phases as Phase 1 and Phase 2, enrollment of 43 participants, and no masking. Allocation is listed as not applicable; the design is not a randomized comparison. Participants in the study group were to receive a single booster dose on Day 0.
The registry lists the study start as 2012-09 and primary completion as 2012-11. Its stated purpose was to assess immunogenicity and safety. The primary objective concerned immunogenicity, and the secondary objective concerned safety. The sponsor is Sanofi Pasteur, a Sanofi Company. The record lists pertussis, tetanus and diphtheria as conditions.
A single-group design can describe outcomes observed after vaccination, but without a separate comparator it cannot estimate a between-group treatment contrast. In particular, any antibody result would describe the observed participants at the stated follow-up, not how their results compare with an alternative intervention under the same conditions. The lack of masking is part of the recorded design; the record does not explain whether or how this affected outcome assessment.
The record lists ten outcome measures, but it does not report the primary endpoint results or analyses. It also does not report a statistical analysis plan, sample-size justification, or further details of the study procedures. The planned dose and time point are stated, but additional follow-up schedules and the timing or duration of safety collection are not reported in the registry record. Those omissions limit how fully the study’s conduct and the scope of its findings can be reconstructed from the registry entry.
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 43 participants that met all the inclusion criteria but none of the exclusion criteria were enrolled and vaccinated in the study.
Overall Study
| Stage | Study Group |
|---|---|
| STARTED | 43 |
| COMPLETED | 43 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Seroprotection to diphtheria and tetanus antigens were determined in the Immunology Analysis Set
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 | Study Group |
|---|---|---|
| Participants analysed | 43 | |
| Age, Categorical: <=18 years | Participants | 43 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age, Continuous | Years | 11.4 (SD 0.5) |
| Sex: Female, Male: Female | Participants | 23 |
| Sex: Female, Male: Male | Participants | 20 |
| Region of Enrollment: Japan | Participants | 43 |
6. Primary Endpoint
The registry lists the primary outcome as Percentage of Participants With Seroprotection Against Diphtheria and Tetanus Antigens Following Vaccination With ADACEL®, measured over Day 28 post-vaccination.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Percentage of Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the percentage of participants with seroprotection against diphtheria and tetanus antigens following vaccination with ADACEL®. Seroprotection is defined as an antibody concentration of at least 0.1 IU/mL after vaccination, with assessment at Day 28 post-vaccination. The registry states that seroprotection to the antigens was determined in the Immunology Analysis Set.
As a statistical measure, a percentage expresses how common a defined outcome was in the assessed group. Here, the outcome is meeting the antibody threshold. Such a threshold makes the endpoint interpretable as a proportion of participants whose measured antibody concentration reached a prespecified level, rather than as a comparison of average concentrations. General statistical context: a threshold-based endpoint can be useful when a study is interested in the proportion attaining a defined antibody level, but it does not describe the full distribution of antibody concentrations.
The registry record does not report the percentage, the number of participants meeting the threshold, or a confidence interval. Nor does its wording make clear whether the reported endpoint was intended to present separate results for each antigen or a single result requiring seroprotection against both. Those details are important to interpretation and are not reported in the registry record. The endpoint definition alone does not reveal the observed immunogenicity result.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record gives the primary endpoint’s definition and follow-up time but does not report its observed value. It therefore is not possible to state what percentage of participants reached the antibody threshold, how many participants contributed to that result, or how uncertain the estimate was. No primary endpoint analysis or confidence interval is reported in the registry record. The stated endpoint should not be mistaken for an observed finding.
The safety information is more specific. In the study group, 0 participants were recorded as affected by a serious adverse event among 43 at risk. The record also reports 39 participants affected in the other adverse-event category among 43 at risk. These are descriptive counts for the study group. The registry does not report event-level details, the assessment period, or the relationship of events to vaccination. Deaths are not reported in the registry record.
The single-group design is central to interpretation. The record describes outcomes after a booster dose, but contains no control group for comparison. It therefore cannot support a comparative estimate of differences between ADACEL® and another intervention, or distinguish changes associated with vaccination from changes that might occur for other reasons. This limitation applies even if a numerical antibody result is available elsewhere; the registry entry itself does not provide that result.
The study is listed as completed, but completion does not substitute for reporting outcome estimates. Likewise, the fact that the registry lists ten outcome measures does not show what their results were. The record lists no analyses, so there are no reported statistical tests or adjusted estimates to interpret. No conclusion about statistical significance, precision, or the consistency of findings across outcomes can be drawn from the information recorded.
General statistical context: a point estimate describes the observed result in the analyzed participants, while a confidence interval conveys uncertainty around that estimate under the analysis assumptions. Neither can be interpreted for this primary endpoint without a reported estimate and interval. The enrollment figure is not the same as the number analyzed for immunogenicity; the size and handling of the Immunology Analysis Set are not reported in the registry record.
For safety, zero participants recorded with a serious adverse event is a count in this study group, not proof that serious events cannot occur. With no comparison group and no reported detail about follow-up or event attribution, the count does not quantify a comparative risk or establish causation. The other adverse-event count is likewise descriptive and should not be interpreted as a causal effect or as a measure of severity without further information.
9. Statistical Methods Explained
General statistical context: the primary outcome is a binary, threshold-based outcome at the participant level. A participant either meets the stated antibody threshold or does not, for the antigen or antigens being assessed. The study’s endpoint is then expressed as a percentage of participants meeting that definition. The registry record specifies the threshold and the time point, but does not report the observed percentage or the number assessed.
What does a percentage estimate?
For a binary outcome, the sample percentage is a descriptive estimate of the proportion meeting the defined criterion in the analyzed group. Its interpretation depends on a clear numerator and denominator: the numerator is the number meeting the criterion, and the denominator is the number assessed for that outcome. The registry record reports enrollment of 43, but it does not report the immunogenicity numerator or denominator. Enrollment alone cannot be substituted for the analysis population, because the record identifies an Immunology Analysis Set without stating how many participants were included.
A percentage also does not show how far antibody concentrations were above or below the threshold. Participants with different concentrations can fall on the same side of a cutoff, and a small change around a cutoff can change a participant’s classification. General statistical context: continuous antibody measurements and threshold-based proportions answer related but different questions. The registry’s stated primary outcome is the proportion meeting the threshold, not a reported comparison of average antibody concentration.
What would a confidence interval add?
General statistical context: a confidence interval describes the uncertainty associated with an estimate under a specified statistical method. For a percentage, it indicates a range of values compatible with the observed data and method; narrower intervals generally indicate greater precision. Its width depends on the amount of information and the observed proportion, among other considerations. The registry record does not report a confidence interval for the primary endpoint, so its precision cannot be assessed from this entry. No interval should be inferred from the enrollment count alone.
A confidence interval is not a guarantee that the true value lies within its particular limits, nor does it resolve limitations in the design or measurement. In this study, even a reported interval would describe the endpoint in the analyzed single group, not a contrast with an unobserved control group. General statistical context: precision and causal interpretation are separate issues. An estimate can be precise for a particular group while still not providing a comparative treatment effect.
What can the design estimate?
The study is recorded as single group, with no masking and allocation not applicable. General statistical context: a single-group study can estimate a descriptive outcome among participants who received the intervention, provided the outcome and analyzed population are reported. It does not produce a randomized between-group contrast. Without a comparator, there is no concurrent group to help separate outcomes associated with the intervention from background changes or other influences.
The registry lists the study as Phase 1 and Phase 2 and reports a single booster dose on Day 0, with the primary immunogenicity time point at Day 28 post-vaccination. The record does not report the detailed statistical methods used for analysis. It is therefore not possible to identify an estimator, confidence-interval method, hypothesis test, or model as the study’s actual analytic approach. General explanations of these methods should not be read as a description of the unreported study plan.
How should planning illustrations be read?
The planning assumptions described for illustrations specify a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with an effect framed as a stated fraction of the observed effect. These are planning assumptions, not a record of the trial’s design: the trial itself is recorded as a single-group study. The registry record does not report an observed primary effect from which such an illustration could be evaluated. Any sample-size illustration based on an effect is a planning exercise, not an observed study result or observed power.
General statistical context: sample-size planning asks how much information a future design might require under specified assumptions. Its answer depends on the assumed effect, variability or event rate, analysis, allocation, and error rate. If an assumed effect is changed, the planning result can change as well. Such calculations do not establish that a completed study had adequate power, and they cannot replace a reported estimate with its uncertainty. The assumptions listed for an illustration should not be mistaken for evidence that this single-group trial used a two-arm design or those methods.
What does the absence of listed analyses mean?
The registry lists no analyses. This means the record does not give inferential results to interpret; it does not establish which methods may or may not have been used in the conduct of the study. In particular, there are no registry-reported p-values, adjusted estimates, or analysis details for the primary endpoint. General statistical context: a p-value, when reported, addresses compatibility between data and a specified null hypothesis under model assumptions; it is not a measure of effect size or clinical importance. No such interpretation is possible without a reported test and its context.
The main statistical conclusion is therefore about reporting, not the magnitude of immunogenicity: the registry defines a threshold-based endpoint and identifies an analysis population, but does not provide the primary result, its uncertainty, or the analysis methods. Safety counts are reported descriptively, with important details about collection and interpretation absent.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists ten outcome measures and identifies one primary endpoint concerning seroprotection against diphtheria and tetanus antigens. It does not report whether statistical testing was performed across outcomes, whether any multiplicity adjustment was planned, or how the primary endpoint was distinguished analytically from other outcomes. No analysis results are listed, so there are no reported p-values or confidence intervals for which multiplicity handling can be assessed. Any statistical plan for controlling false-positive findings is not reported in the registry record.
The primary endpoint is assigned to the Immunology Analysis Set. The record does not report the number of participants in that set, how it was defined, or how it differed from enrollment. It also does not report how missing antibody measurements or participants without a Day 28 assessment were handled. There is no reported imputation method, missing-data sensitivity analysis, or account of exclusions from the immunogenicity analysis.
General statistical context: missing outcome data can affect both the denominator of a percentage and the interpretation of who the estimate represents. The consequences depend on why measurements are missing and on the analysis approach; without those details, the direction or size of any effect cannot be established. A named analysis population is not, by itself, enough to determine which participants were included or how incomplete data were treated.
The record does not provide enough information to assess whether outcome reporting was selective, how safety populations were defined, or whether the same participants contributed to immunogenicity and safety summaries. These details are not reported in the registry record and should not be inferred from the enrollment number or the list of outcomes.
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 |
|---|---|---|---|
| Study Group | 0 | 43 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5.00% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Study Group | 39 of 43 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Study Group |
|---|---|---|
| Solicited injection site Pain | General disorders | 37 of 43 |
| Myalgia | General disorders | 17 of 43 |
| Solicited injection site Swelling | General disorders | 12 of 43 |
| Malaise | General disorders | 11 of 43 |
| Solicited injection site Erythema | General disorders | 9 of 43 |
| Fever | General disorders | 9 of 43 |
| Headache | Nervous system disorders | 8 of 43 |
| Nasopharyngitis | Infections and infestations | 7 of 43 |
For the study group, the registry reports 0 participants affected by a serious adverse event among 43 at risk. It also reports 39 participants affected in the other adverse-event category among 43 at risk. These are participant counts, not event counts or percentages. The registry does not report deaths, so death information is not reported in the registry record.
The serious-event figure is a descriptive observation in this study group. It does not establish that serious events are impossible, and it does not provide a comparison with another group. The record does not give the observation period, event descriptions, severity details beyond the serious-event category, or information about whether events were considered related to vaccination. The list of serious-event terms is empty, so no specific serious events are described in the registry entry.
The other adverse-event category should be read separately from the serious-event count. The registry does not provide the event terms or further details needed to characterize these reports. General statistical context: safety counts depend on how events were defined, collected, and followed; interpretation requires those details as well as the number of participants at risk. The counts alone do not establish causation or comparative safety.
12. What the Result Does, and Does Not, Mean
The registry record establishes that the study was designed to assess immunogenicity and safety after a single ADACEL® booster dose in Japanese adolescents. It defines seroprotection using an antibody concentration threshold of at least 0.1 IU/mL and names Day 28 post-vaccination as the primary assessment time. It also reports descriptive safety counts for the study group. These are details about the study question, endpoint definition and recorded safety data.
The record does not report the primary immunogenicity percentage, the participants meeting the threshold, or uncertainty around an estimate. As a result, it does not allow a reader to judge the observed level or precision of seroprotection from this registry entry. The phrase “primary endpoint” identifies what was intended to be assessed; it is not itself a result. The endpoint description also does not make clear whether the intended result was antigen-specific for each of diphtheria and tetanus or required both.
The study’s single-group design means that its recorded observations do not provide a direct comparison with a control group or another vaccine. General statistical context: a descriptive result in an exposed group and a comparative treatment effect are different quantities. Without a comparator, the record cannot estimate a between-group difference or isolate what would have happened to similar participants without the booster.
The safety data report no participants affected by a serious adverse event among 43 at risk, alongside 39 participants affected in the other adverse-event category among 43 at risk. These counts do not establish event causation, provide a comparative safety estimate, or describe the range and timing of events. Deaths are not reported in the registry record.
Accordingly, the record supports a limited account of the study’s design and safety counts, but not a conclusion about the primary immunogenicity result, its precision, or comparative effects. The absence of reported analyses and missing-data details further limits statistical interpretation. The findings should not be extended beyond the outcomes and participants described in the registry record.
13. Why This Trial Matters Statistically
This trial illustrates the difference between a clearly defined endpoint and a reported endpoint result. The registry specifies a seroprotection threshold, the antigens of interest, a post-vaccination assessment time, and the analysis population name. Those details identify what investigators intended to measure. Without the observed percentage, numerator, denominator, or uncertainty, however, a reader cannot assess the primary immunogenicity finding statistically.
The single-group structure is also important. Descriptive outcomes can be useful for characterizing participants in a study, but they do not answer a comparative question by themselves. A planning illustration framed around two arms does not alter the recorded design, which has one study group and no like-for-like control comparison. Keeping planning assumptions separate from trial conduct and observed results prevents a sample-size calculation from being mistaken for evidence of statistical power or treatment effect.
The safety entry provides participant counts, but interpretation still depends on definitions, follow-up, and event details. This makes the record a useful example of why safety summaries need context in addition to counts. General statistical context: a count without a comparator is descriptive, and a count without a clear observation window cannot convey the full scope of exposure to risk.
Finally, naming an analysis set does not explain how missing data were handled or how many participants contributed. A statistically interpretable registry record needs outcome estimates and enough methodological detail to understand who was analyzed and how uncertainty was assessed. In this entry, the limits of reporting are themselves the main statistical lesson: study objectives and definitions should not be confused with empirical results.
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 primary limitation for interpretation is that the registry does not report the primary immunogenicity result, despite specifying its threshold and Day 28 time point. It also does not report an estimate’s uncertainty, the number assessed, or the number meeting the criterion. The Immunology Analysis Set is named, but its size and membership are not reported in the registry record. The endpoint wording does not clarify whether results were intended separately for each antigen or as a combined criterion.
The single-group design provides no concurrent comparator. Consequently, outcomes cannot be interpreted as a between-group effect, and there is no randomized control contrast in the record. Masking is recorded as none. The registry does not explain the implications of that design choice for outcome measurement or assessment.
Additional statistical details are unavailable. The record does not report the statistical analysis plan, methods for confidence intervals or hypothesis tests, sample-size justification, missing-data handling, or multiplicity procedures. Although ten outcome measures are listed, no analyses are reported. These omissions prevent assessment of the analytic approach, precision, and consistency across outcomes.
Safety interpretation is limited by the absence of event descriptions, collection period, attribution, and detailed definitions for the other adverse-event category. Death information is not reported in the registry record. The reported participant counts should therefore be treated as descriptive rather than as comparative or causal estimates.
The record identifies enrollment of 43 and reports 43 at risk for the listed safety groups, but it does not establish that the same number contributed to immunogenicity analyses. Results from the registry entry cannot be generalized beyond its recorded study population and outcomes without additional evidence.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis Vaccine (ADACEL®) as a Booster in Adolescents — NCT01689324.
- Registry record last updated 2014-02-21; status last verified 2014-02.
- Results first posted 2014-02-21.
- 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
NCT01689324 is a completed, single-group study of ADACEL® as a booster in Japanese adolescents, recorded as Phase 1 and Phase 2. The registry reports enrollment of 43, no masking, and administration of a single dose on Day 0. The primary endpoint concerns the percentage with seroprotection against diphtheria and tetanus antigens at Day 28, defined by an antibody concentration of at least 0.1 IU/mL.
The primary immunogenicity result and statistical analyses are not reported in the registry record. Safety reporting lists 0 participants with a serious adverse event among 43 at risk and 39 participants affected in the other adverse-event category among 43 at risk. Deaths are not reported. The entry does not provide the analysis-set size, missing-data methods, or detailed safety-event information.