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 BK1301 (DTaP Vaccine) as a Booster in Adolescents (NCT02118961), a randomized phase 3 study. The primary outcome is Percentage of Participants With Booster Responses for Anti-diphtheria Toxoid (Anti-D) and Anti-tetanus Toxoid (Anti-T) Antibodies.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02118961 |
| Phase | Phase 3 |
| Condition | Diphtheria, Tetanus, Pertussis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 446 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Tanabe Pharma Corporation |
| Results posted | Yes |
2. Clinical Question
Population
Adolescents receiving a booster vaccination. The registry record does not report a more detailed age range or describe eligibility criteria, baseline health characteristics, or the analysis population for the primary endpoint.
Intervention
BK1301, described as a diphtheria and tetanus toxoids and acellular pertussis vaccine adsorbed (DTaP vaccine), given as a booster. The registry record does not give further details about administration or the dose.
Comparator
Adsorbed diphtheria-tetanus combined toxoid, referred to as DT toxoid in the registry record. The trial compares the antibody response after BK1301 with the response after this active comparator.
Primary question
Whether BK1301 is non-inferior to DT toxoid for booster responses in anti-diphtheria toxoid (anti-D) and anti-tetanus toxoid (anti-T) antibodies. The study description also gives a separate objective: to confirm that anti-pertussis toxoid (anti-PT) and anti-filamentous hemagglutinin (anti-FHA) booster responses exceed the stated 80% threshold among BK1301 recipients.
The primary endpoint concerns the percentage of participants meeting the stated booster-response definition for anti-D and anti-T. That definition requires a post-vaccination titer of at least 0.4 IU/mL and a post/pre titer of at least 4. Measurements are described for pre-vaccination and 28-42 days after vaccination.
The registry record identifies these objectives but does not report numerical primary endpoint results or the non-inferiority margin. It therefore does not establish from the posted results whether the comparison met its non-inferiority criterion. The additional anti-PT and anti-FHA objective is described, but numerical results for that objective are not reported in the registry record either.
3. Trial Design
This was a randomized, quadruple-masked, parallel-group Phase 3 study of BK1301 as an adolescent booster. Its active comparator was adsorbed diphtheria-tetanus combined toxoid (DT toxoid). The registry record lists enrollment as 446. It records the study as completed, with a start date of 2014-04 and primary completion in 2014-08.
The two groups received different biological interventions: BK1301 or DT toxoid. Random allocation is a design feature intended to make treatment groups comparable on average, including for factors that may affect antibody response. It does not guarantee that every measured or unmeasured characteristic will be balanced, and the registry record does not report group-level baseline characteristics with which to assess balance.
Quadruple masking indicates that the record characterizes the study as masked at four levels, but it does not identify those levels or explain how masking was maintained. The participant ages beyond the description “adolescents,” the precise recruitment setting, eligibility criteria, and details of vaccine administration are not reported in the registry record.
The stated primary assessment compares the percentages with anti-D and anti-T booster responses, measured pre-vaccination and 28-42 days after vaccination. The study description frames that comparison as a non-inferiority objective. A non-inferiority conclusion depends on a prespecified margin and an appropriate confidence interval or test; the margin and trial-specific analysis method are not reported in the registry record. The listed enrollment alone does not show whether the study had adequate precision for its planned objective.
Other listed outcomes include antibody titers, geometric mean titer ratios, participants above protocol-defined antibody cut-offs, and adverse events. The record lists these outcome types but does not provide numerical results for the immunogenicity outcomes. It also does not report the statistical analysis plan, analysis populations, or handling of missing measurements.
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 | BK1301 | DT Toxoid |
|---|---|---|
| STARTED | 224 | 222 |
| COMPLETED | 223 | 222 |
| NOT COMPLETED | 1 | 0 |
Reasons for not completing this period:
| Reason | BK1301 | DT Toxoid |
|---|---|---|
| Withdrawal by Subject | 1 | 0 |
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 | BK1301 | DT Toxoid | Total |
|---|---|---|---|---|
| Participants analysed | 224 | 222 | 446 | |
| Age, Categorical: <=18 years | Participants | 224 | 222 | 446 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 | 0 | 0 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Female | Participants | 113 | 104 | 217 |
| Sex: Female, Male: Male | Participants | 111 | 118 | 229 |
6. Primary Endpoint
The registry lists the primary outcome as Percentage of Participants With Booster Responses for Anti-diphtheria Toxoid (Anti-D) and Anti-tetanus Toxoid (Anti-T) Antibodies, measured over pre-vaccination and 28-42 days after vaccination.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | percentage of Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the percentage of participants with booster responses for anti-diphtheria toxoid (anti-D) and anti-tetanus toxoid (anti-T) antibodies. A response is defined using both an absolute post-vaccination titer and a change relative to the pre-vaccination titer: the post titer must be at least 0.4 IU/mL, and the post/pre titer must be at least 4. The stated assessment period is pre-vaccination and 28-42 days after vaccination.
This endpoint converts antibody measurements into a responder classification. In general, a prespecified response definition can make a result easier to interpret against a biological or protocol threshold. It also means that participants close to a cut-off may be classified differently despite having similar underlying titers. The definition combines an absolute level with a relative increase, so neither condition alone is sufficient to meet the recorded definition.
The percentage endpoint is relevant to the stated non-inferiority comparison because the study description asks whether the proportion meeting the response definition with BK1301 is not unacceptably lower than with DT toxoid. However, the registry record does not report the non-inferiority margin or numerical response percentages and confidence intervals. The primary outcome listing also indicates that multiple categories or time points were not reduced to one comparison. Consequently, the record does not support a single numerical estimate of the primary comparison.
Anti-PT and anti-FHA responses are described as a further immunogenicity objective, with a stated threshold of more than 80% among BK1301 recipients. Numerical results for that objective are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a randomized comparison of BK1301 with DT toxoid and defines the primary endpoint as the percentage meeting anti-D and anti-T booster-response criteria. It does not report the numerical primary endpoint results. In particular, there are no posted response percentages, confidence intervals, or treatment comparison estimate in the record. The direction, size, and precision of the primary immunogenicity comparison therefore cannot be assessed from these registry entries.
The study objective is non-inferiority, not simply a test for any difference. In general, a non-inferiority assessment asks whether the observed results are sufficiently compatible with a prespecified acceptable loss in effect. The margin is essential to that interpretation, because it defines what degree of lower response would still satisfy the study objective. The margin and the trial-specific decision rule are not reported in the registry record. Without those details and the endpoint results, it is not possible to determine whether the stated objective was met.
The record describes a separate aim concerning anti-PT and anti-FHA booster responses, requiring that responses exceed 80% among participants who received BK1301. It does not report the relevant percentages or their uncertainty. The listed secondary outcomes include percentages above protocol-defined cut-offs, geometric mean titers, geometric mean titer ratios, and adverse events. Numerical immunogenicity results for those outcomes are not reported in the registry record.
Safety entries show zero serious adverse events recorded among 223 participants at risk in the BK1301 group and zero among 222 participants at risk in the DT toxoid group. Other adverse events are recorded for 200 participants in the BK1301 group and 194 in the DT toxoid group. These figures are descriptive registry counts. The record does not provide event types for the other adverse events, exposure-adjusted rates, or a statistical comparison. Zero recorded serious events in these groups is not proof that serious events cannot occur.
There is no numerical primary immunogenicity result on which to judge precision, and no trial-specific analysis details with which to evaluate the reported safety counts. The record lists a planned sample-size illustration based on an observed effect, but any such illustration is a planning calculation, not observed power and not evidence that the study met its objective. The illustration's numerical outputs are not reported in the registry record.
9. Statistical Methods Explained
Clinical-trial results need to be read in relation to the outcome definition, comparison, and uncertainty. In this study, the recorded primary outcome is a percentage: the proportion meeting a defined anti-D or anti-T booster-response criterion. A percentage describes how often a binary outcome occurs in a group. It does not show the full distribution of antibody titers, and it depends on the cut-off used to classify a participant as a responder.
What does the response definition capture?
The definition combines a post-vaccination titer of at least 0.4 IU/mL with a post/pre titer of at least 4. The absolute threshold describes a post-vaccination level, while the ratio criterion describes change from the pre-vaccination measurement. Requiring both means that a participant must meet each part of the definition. In general, dichotomizing a continuous measurement can simplify communication, but it discards detail about values within each response category. Small differences around a cut-off may change classification, while larger differences among participants on the same side of the cut-off may not change it.
The listed measurement window is pre-vaccination and 28-42 days after vaccination. Timing matters because an antibody measurement is tied to when it was taken. The registry record does not report how measurements outside this window were treated, whether all measurements were available, or how missing data were handled.
How should a confidence interval be read?
The primary outcome listing specifies a 95% confidence interval as its dispersion measure. In general, a confidence interval conveys the statistical uncertainty around an estimate under the method used to calculate it. A narrower interval indicates greater precision than a wider interval, while an interval that includes a range of plausible values may leave important interpretations unresolved. A confidence interval is not a guarantee that the true value lies within its endpoints, and it does not by itself establish clinical importance.
For a non-inferiority question, the interval must be interpreted against the prespecified non-inferiority margin and in the direction defined by the analysis. The registry record does not state the margin or provide the primary percentages and intervals. Accordingly, no non-inferiority conclusion can be reconstructed from the endpoint description alone. The phrase “95% Confidence Interval” records a planned or listed uncertainty measure; it is not a numerical result.
Why do the analysis details matter?
Randomization supports a causal comparison by assigning participants to study groups without choosing treatment based on their characteristics. The registry record identifies random allocation, but does not give allocation procedures or the trial's statistical analysis plan. In general, analysis choices can affect estimates and uncertainty, particularly when participants lack measurements, depart from assigned treatment, or have different analysis eligibility. The analysis populations and the handling of such cases are not reported in the registry record.
Masking can reduce the influence of expectations on care, outcome assessment, or reporting, depending on which people are masked and how the masking is implemented. The record describes quadruple masking but does not identify the masked roles. It is therefore possible to report the stated design feature, but not to assess masking procedures in detail.
For binary outcomes, a comparison may be expressed through group percentages and a difference or ratio, with an uncertainty interval. These quantities answer different questions: a difference describes the gap between percentages, while a ratio describes their relative scale. No numerical primary comparison is reported in the registry record, so neither its magnitude nor its precision can be described. No new comparison should be inferred from the safety counts.
What is the role of sample-size calculations?
The registry record describes a sample-size planning illustration based on the observed effect, using 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, and that non-time-to-event illustrations are expressed as participants per arm. These are planning assumptions, not evidence of the study's actual design justification. The numerical illustration results and the trial's own sample-size justification are not reported in the registry record.
General sample-size calculations estimate the amount of information that may be needed to detect a chosen effect under stated assumptions. They depend on the target effect, variability or event frequency, error rates, and analysis method. A calculation based on an observed effect is especially dependent on that estimate and should not be treated as observed power. The registry record does not report a trial-specific power calculation or interim-analysis plan.
How should safety counts be interpreted?
Serious adverse event counts describe recorded events in relation to the participants at risk listed for each group. A zero count means no serious adverse events are recorded in those entries; it does not establish zero underlying risk. General interpretation also depends on follow-up duration, event definitions, completeness of reporting, and the specific events observed. Those details are not reported in the registry record. The other adverse-event counts are also descriptive, and no inferential comparison is reported.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists several immunogenicity outcomes, including anti-D and anti-T response percentages, antibody titers, geometric mean titers, geometric mean titer ratios, and anti-PT and anti-FHA outcomes. It also lists adverse events. Considering several outcomes or time points can create a multiplicity issue: in general, the chance of at least one apparently notable finding may increase when many statistical tests are conducted. A planned testing hierarchy or adjustment can clarify how results should be interpreted, but the multiplicity strategy is not reported in the registry record.
The primary outcome description indicates that it has several categories or time points and was not reduced to one comparison. That limits the ability to present a single summary estimate for the primary endpoint from the registry record. It also means the precise analysis structure cannot be inferred from the outcome title. The endpoint's numerical results, any prespecified hierarchy, and the method for combining or separately assessing categories are not reported in the registry record.
Missing data can affect both responder percentages and antibody summaries. In general, the consequences depend on why measurements are missing, how much information is missing, and the analysis method. The registry record does not report missingness, imputation methods, exclusions, or sensitivity analyses. It also does not specify analysis populations, such as the population used for the primary non-inferiority assessment.
The registry record lists 446 for enrollment but does not provide enough analysis detail to connect that figure to endpoint-specific denominators. It does not report a participant disposition account or endpoint-specific numbers analyzed. No assumptions about missing observations or analysis populations should be made from the enrollment entry alone.
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 |
|---|---|---|---|
| BK1301 | 0 | 223 | 0.0% |
| DT Toxoid | 0 | 222 | 0.0% |
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 |
|---|---|
| BK1301 | 200 of 223 |
| DT Toxoid | 194 of 222 |
Most frequent non-serious adverse event terms
| Event term | Organ system | BK1301 | DT Toxoid |
|---|---|---|---|
| Injection site erythema | General disorders | 167 of 223 | 160 of 222 |
| Injection site swelling | General disorders | 162 of 223 | 148 of 222 |
| Injection site pruritus | General disorders | 132 of 223 | 113 of 222 |
| Injection site pain | General disorders | 125 of 223 | 85 of 222 |
| Injection site warmth | General disorders | 115 of 223 | 87 of 222 |
| Injection site induration | General disorders | 95 of 223 | 84 of 222 |
| Headache | Nervous system disorders | 17 of 223 | 13 of 222 |
| Nasopharyngitis | Infections and infestations | 12 of 223 | 15 of 222 |
| Pyrexia | General disorders | 15 of 223 | 3 of 222 |
The serious adverse event entries record zero affected among 223 at risk in the BK1301 group and zero affected among 222 at risk in the DT toxoid group. The number of deaths is not reported in the registry record. The serious-event terms list is empty, so event descriptions are not reported in the registry record.
Other adverse events are recorded for 200 participants in the BK1301 group and 194 in the DT toxoid group, with 223 and 222 respectively listed as at risk. These are registry counts, not a causal comparison. The record does not specify the events included in this category, their severity, duration, timing, or whether they were judged related to vaccination. It also does not report an analysis comparing the groups.
In general, a zero observed serious-event count should be read as no such event recorded in the reported group data, rather than proof that the underlying risk is absent. Interpretation depends on follow-up and completeness of ascertainment, details that are not reported in the registry record. Counts alone do not indicate whether differences between groups are statistically meaningful. The adverse-event entries should be considered separately from the unreported numerical immunogenicity results.
12. What the Result Does, and Does Not, Mean
The registry record describes a randomized, quadruple-masked, parallel-group Phase 3 study comparing BK1301 with DT toxoid as an adolescent booster. It states a non-inferiority objective for anti-D and anti-T booster responses and an additional threshold objective for anti-PT and anti-FHA responses. The primary response definition and assessment period are specified, which helps clarify what the trial intended to measure.
However, the record does not report the numerical primary antibody-response results. It therefore does not establish the observed response percentages, the size or direction of a between-group difference, or the precision of that comparison. The non-inferiority margin and trial-specific statistical decision rule are also not reported. Without those details, the study objective cannot be evaluated from the registry record alone.
The safety entries report no serious adverse events in either group and list other adverse events in both groups. Those entries describe recorded counts; they do not establish that either intervention caused or prevented an event, and they do not provide a statistical comparison. The types of other adverse events and the deaths data are not reported in the registry record.
More generally, a registry outcome listing is not equivalent to a complete report of trial conduct and results. A reader would need numerical outcome estimates, uncertainty intervals, analysis populations, missing-data information, and the prespecified non-inferiority margin to assess the primary comparison fully. Those details are not reported in the registry record. The listed study objectives should therefore be distinguished from evidence that an objective was achieved.
The study record can establish the design features and the outcomes the investigators intended to assess. It cannot, on the information recorded, support a quantitative conclusion about the relative antibody response or the precision of that comparison. Nor can the safety counts alone establish comparative safety.
13. Why This Trial Matters Statistically
This trial raises statistical questions that are common in vaccine immunogenicity studies. Its primary endpoint is a responder percentage based on a defined antibody threshold and a relative increase from baseline. Such endpoints require careful attention to the response definition, timing of measurement, denominator, and uncertainty. Those elements determine what the percentage represents and how comparable group results should be interpreted.
The stated comparison is non-inferiority. That makes the margin central: a result can only be interpreted against the acceptable difference specified before analysis. A randomized design and a confidence interval are important components of such an assessment, but neither replaces the margin or the analysis plan. In this case, the registry record does not report the margin or numerical primary results, illustrating why design objectives alone are not enough to establish the statistical conclusion.
The study also lists several antibody outcomes, including titers and geometric mean titer ratios, as well as responder outcomes and adverse events. Multiple outcomes can provide complementary views of immunogenicity and safety, but they also require a clear analysis strategy. The registry record does not report a multiplicity approach or enough numerical outcome results to compare those measures.
Finally, the entries distinguish serious adverse events from other adverse events, but counts without event descriptions or an analysis plan have limited interpretive reach. This makes the record useful for identifying the trial's broad design and aims, while underscoring the need for detailed results and methods when judging statistical evidence.
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 does not report numerical results for the primary anti-D and anti-T booster-response endpoint. It also does not provide the non-inferiority margin, the primary comparison estimate, or its confidence interval. These omissions prevent assessment of whether the stated non-inferiority objective was met or how precisely the comparison was estimated.
The additional anti-PT and anti-FHA objective is described, but its numerical results are not reported in the registry record. Numerical results for the listed secondary immunogenicity outcomes are also not reported. The record lists nine outcome measures and zero analyses, but does not provide a results narrative explaining the analysis of each outcome.
Important design and analysis details are not reported in the registry record, including eligibility criteria, the adolescent age range, allocation procedures, the roles covered by quadruple masking, analysis populations, and the statistical analysis plan. Missing measurements, exclusions, and sensitivity analyses are not described. The record also does not report a trial-specific sample-size justification or interim-analysis plan.
Safety information is limited to group counts. The record does not describe other adverse-event terms, follow-up duration, deaths, or the method used to collect and classify events. The empty serious-event terms list does not supply additional event detail. These omissions restrict interpretation of both the safety counts and the completeness of safety reporting.
The record lists a planning illustration based on the observed effect, but its numerical outputs are not reported in the registry record. Such an illustration is not a substitute for the trial's own design justification or for observed outcome estimates.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of BK1301 (DTaP Vaccine) as a Booster in Adolescents — NCT02118961.
- Registry record last updated 2026-01-06; status last verified 2025-12.
- Results first posted 2016-11-21.
- 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
NCT02118961 is a completed randomized, quadruple-masked, parallel-group Phase 3 study of BK1301 as an adolescent booster, compared with DT toxoid. The registry record lists enrollment as 446, a start date of 2014-04, and primary completion in 2014-08.
The primary outcome is the percentage meeting anti-D and anti-T booster-response criteria, assessed pre-vaccination and 28-42 days after vaccination. The study description states a non-inferiority objective and a further anti-PT and anti-FHA response objective. Numerical immunogenicity results and the non-inferiority margin are not reported in the registry record.
The safety entries list zero serious adverse events in each group and other adverse events for 200 participants in the BK1301 group and 194 in the DT toxoid group. Deaths and serious-event terms are not reported in the registry record. Statistical analysis details, missing-data handling, and analysis populations are also not reported.