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 Safety and Immunogenicity of DAPTACEL® as 5th Dose in Children 4 to 6 Years Old After 4 Doses of Pentacel™ or DAPTACEL® (NCT00258895), a non-randomized phase 3 study. The primary outcome is Percentage of Participants Reporting Solicited Local or Systemic Reactions Post-Dose 5 of DAPTACEL® Vaccination.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00258895 |
| Phase | Phase 3 |
| Condition | Diphtheria, Tetanus, Pertussis |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 649 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sanofi Pasteur, a Sanofi Company |
| Results posted | Yes |
2. Clinical Question
Population
Children 4 to 6 years old who had previously received 4 doses of DAPTACEL® or Pentacel™. The trial record lists 649 enrolled participants.
Intervention
Participants received DAPTACEL® as a fifth dose. The stated primary objective was to present its safety profile and antibody responses after vaccination.
Comparator
The record distinguishes children previously immunized with DAPTACEL® from those previously immunized with Pentacel™. This was a non-randomized comparison, not a randomized control comparison.
Primary question
What percentage of participants reported solicited local or systemic reactions during 0 to 7 days after the fifth DAPTACEL® dose? The numerical result for this endpoint is not reported in the registry record.
The study also set out to present pre-dose and post-dose antibody responses to the antigens in DAPTACEL®. An observational objective was to compare these responses under equivalence criteria. The record does not report numerical antibody results, the equivalence margins, or the statistical results for that objective. It also describes objectives concerning anti-poliovirus antibody measures in participants receiving other vaccinations concurrently.
The clinical question is therefore primarily descriptive in the available record: it concerns reactions reported after a fifth dose, with participants grouped by earlier vaccine history. The groups were not formed by random assignment. Any difference between their outcomes could reflect prior vaccine history or other group differences, so the comparison cannot be interpreted as if allocation had made the groups interchangeable. The record does not establish a causal comparison between the prior-vaccination groups.
3. Trial Design
This is a phase 3 study with a parallel-group model and non-randomized allocation. Masking is listed as none. The registry record lists 649 participants enrolled and a completed status. The recorded study start is 2005-03, and primary completion is recorded as 2006-12. Sanofi Pasteur, a Sanofi Company, is listed as sponsor.
The two groups are described by their earlier immunization history. Participants in the DAPTACEL®-Primed group received Daptacel in Study P3T06; participants in the Pentacel®-Primed group received Pentacel in Study P3T06. Both groups were assessed after receiving DAPTACEL® as a fifth dose. The record lists 487 participants at risk in the DAPTACEL®-Primed group and 162 in the Pentacel®-Primed group for the reported safety-event figures.
Because the trial was non-randomized and unmasked, the group contrast is observational. Randomization can help balance measured and unmeasured characteristics on average; that protection does not apply to a comparison based on pre-existing vaccination history. The record does not describe adjustment methods that might address differences between groups, and such methods should not be presumed.
The stated objectives include presenting safety and antibody responses, comparing antibody responses under equivalence criteria, and presenting anti-poliovirus measures for participants receiving concurrent IPV and MMR doses. The record does not report the full protocol, eligibility criteria, allocation process beyond its non-randomized status, or details of how each objective was analyzed. Numerical results for the primary endpoint 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 649 participants who met the inclusion and exclusion criteria were enrolled and vaccinated.
Overall Study
| Stage | DAPTACEL®-Primed | Pentacel®-Primed |
|---|---|---|
| STARTED | 487 | 162 |
| COMPLETED | 477 | 159 |
| NOT COMPLETED | 10 | 3 |
Reasons for not completing this period:
| Reason | DAPTACEL®-Primed | Pentacel®-Primed |
|---|---|---|
| Lost to Follow-up | 3 | 1 |
| Protocol Violation | 6 | 2 |
| Withdrawal by Subject | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: Safety analysis was on all enrolled and vaccinated participants with available reaction data, intent-to-treat population.
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 | DAPTACEL®-Primed | Pentacel®-Primed | Total |
|---|---|---|---|---|
| Participants analysed | 487 | 162 | 649 | |
| Age, Categorical: <=18 years | Participants | 487 | 162 | 649 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 | 0 | 0 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Age, Continuous | Years | 4.1 (SD 0.14) | 4.1 (SD 0.16) | 4.1 (SD 0.14) |
| Sex: Female, Male: Female | Participants | 244 | 83 | 327 |
| Sex: Female, Male: Male | Participants | 243 | 79 | 322 |
| Region of Enrollment: United States | participants | 487 | 162 | 649 |
6. Primary Endpoint
The registry lists the primary outcome as Percentage of Participants Reporting Solicited Local or Systemic Reactions Post-Dose 5 of DAPTACEL® Vaccination, measured over 0 to 7 days Post-Dose 5.
| 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 reporting solicited local or systemic reactions after the fifth DAPTACEL® dose. Its stated observation period is 0 to 7 days post-dose. The analysis population is described as all enrolled and vaccinated participants with available reaction data, identified in the record as the intent-to-treat population.
A percentage endpoint represents the proportion of participants in a defined group who experience or report an event. In general, this kind of measure is useful for describing how often specified reactions occur during a stated observation period. Local and systemic reactions cover different kinds of reported symptoms; the record does not provide a list of the solicited reactions or their individual definitions.
For interpretation, the group denominator and the completeness of reaction reporting matter. The stated analysis population excludes enrolled and vaccinated participants without available reaction data, so the result would describe those with usable reaction information rather than necessarily every enrolled participant. The registry record does not report the numerical percentage, event counts, or missing reaction-data counts for this primary endpoint. It therefore does not support a quantitative estimate of the frequency or precision of solicited reactions from the primary outcome.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a safety endpoint and several antibody-response objectives, but it does not report numerical results for the primary solicited local or systemic reaction endpoint. It also does not report numerical pre-dose or post-dose antibody results. Accordingly, the available record cannot establish the observed frequency of the primary reactions or the magnitude and precision of antibody responses.
The adverse-event information does report serious-event counts by prior-vaccination group: 5 affected participants among 487 at risk in the DAPTACEL®-Primed group and 3 among 162 at risk in the Pentacel®-Primed group. It also lists other adverse-event counts of 62 among 487 and 55 among 162, respectively. These are descriptive counts, not an adjusted comparison. The record does not provide a statistical comparison or establish that events were caused by vaccination.
The groups reflect different prior vaccine histories and were not randomized. That matters because measured or unmeasured differences between groups may be associated with outcomes. Even when two groups have different observed counts, a non-randomized comparison alone does not establish that prior vaccine history caused the difference. No adjustment analysis is reported in the registry record.
The antibody-comparison objective refers to equivalence criteria. Equivalence requires assessing whether a confidence interval for the group contrast falls within pre-specified bounds that represent an acceptably small difference. The registry record does not report those bounds, the antibody results, or the corresponding confidence intervals. The stated objective is not evidence that equivalence was demonstrated.
In general, a confidence interval expresses the range of values compatible with the data and a specified statistical procedure. A narrow interval indicates greater precision than a wide one, but precision alone does not resolve bias from non-randomized group formation. Since primary endpoint estimates and their intervals are not reported, the precision of the primary safety estimate cannot be assessed. No p-values or analysis results for the stated objectives are reported in the registry record.
Overall, the posted information describes the study question, design, and selected adverse-event figures, but it is insufficient for a complete statistical assessment of the primary endpoint or antibody objectives. The counts should be read as recorded safety data, not as proof of a difference, equivalence, or causal effect.
9. Statistical Methods Explained
The methods information supports a limited statistical description. The primary endpoint is a percentage, so it is a binary-outcome summary: participants are classified according to whether they reported a solicited local or systemic reaction in the stated period. The record identifies an intent-to-treat safety population composed of enrolled and vaccinated participants with available reaction data. It does not provide the actual endpoint counts, percentages, confidence intervals, or a model used for inference.
What does a percentage measure?
As a general statistical explanation, a percentage for a binary outcome describes the fraction of participants with an event among a stated denominator. Its interpretation depends on what counts as an event, the follow-up period, and which participants contribute data. Here, the endpoint description gives the broad reaction categories and a 0 to 7 days timeframe, but the registry record does not report the individual reaction definitions or the primary endpoint result.
For a group comparison, the difference between two percentages can be described as an absolute contrast, while a ratio can describe a relative contrast. These are different measures and can convey different aspects of the data. No numerical contrast for the primary endpoint is reported in the registry record, and no new contrast can be inferred from the other adverse-event counts.
Why does allocation matter?
As a general principle, random assignment aims to make comparison groups similar in expectation at baseline. In this study, allocation is listed as non-randomized, and group membership reflects earlier vaccine history. Consequently, any comparison between the DAPTACEL®-Primed and Pentacel®-Primed groups may be affected by differences that existed before the fifth dose. A statistical adjustment can sometimes address measured differences, but it cannot automatically remove bias from unmeasured factors. The registry record does not report an adjusted analysis.
The parallel-group description means the record treats the prior-vaccination groups as distinct groups assessed after the fifth dose. No crossover or within-person comparison is described in the listed design. The record does not give enough detail to characterize all visit schedules or the timing of antibody specimen collection.
How should equivalence be assessed?
As a general statistical concept, an equivalence analysis asks whether the data are sufficiently precise to rule out differences larger than an agreed margin in either direction. It is not enough for a conventional test to fail to detect a difference. The margin must be specified, and the confidence interval for the relevant contrast must fit within it under the pre-specified analysis. Although an observational objective mentions equivalence criteria for antibody responses, the margins, analysis method, and results are not reported in the registry record. Equivalence therefore cannot be concluded from the objective alone.
What do confidence intervals and significance tests contribute?
In general, a confidence interval communicates statistical uncertainty around an estimate, whereas a significance test addresses compatibility with a specified null hypothesis under its assumptions. Neither measure resolves weaknesses in study design, and neither establishes that an observed association is causal. The registry record does not report confidence intervals, p-values, or the statistical test used for the primary outcome.
The record describes a sample-size planning illustration based on a stated fraction of an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It also states that such figures are planning illustrations, not observed power. The numerical planning results and the observed effect needed to interpret those illustrations are not reported in the registry record. They cannot be treated as the trial's design justification or as evidence about the probability of detecting an effect.
What assumptions could affect the analysis?
As a general matter, methods for binary outcomes rely on a clearly defined event, a suitable denominator, and appropriate handling of incomplete observations. Inference may also depend on whether observations are independent and whether the chosen statistical model represents the data adequately. The registry record does not describe a model, covariate adjustment, or assumptions used for the primary endpoint. The available information does not permit a check of those assumptions.
The safety counts identify participants at risk and participants affected for serious and other adverse events. They are useful descriptive summaries, but counts alone do not provide a measure of statistical uncertainty or establish a between-group difference. The record does not report inferential analyses for these figures. The serious-event term percentages are listed as recorded; their calculation details and uncertainty are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The stated objectives include safety, antibody responses to DAPTACEL® antigens, an equivalence comparison of antibody responses, and anti-poliovirus antibody measures in subsets receiving concurrent vaccinations. Multiple objectives and outcome measures can create a multiplicity issue: when many hypotheses are examined, the chance of at least one apparently notable result may increase. As a general statistical practice, a trial may specify which outcomes are primary and how statistical testing will be controlled or interpreted.
The registry record identifies one primary endpoint concerning solicited local or systemic reactions after the fifth dose. It lists 5 outcome measures overall, but does not provide the complete outcome results or report a multiplicity strategy. Whether the protocol adjusted for multiple comparisons, designated a testing hierarchy, or treated secondary analyses as descriptive is not reported in the registry record. The objective's reference to equivalence does not supply the missing margins or analysis details.
Missing-data handling is also not described in sufficient detail. For the primary endpoint, the stated safety analysis includes enrolled and vaccinated participants with available reaction data. The record does not report how many participants lacked such data, why data were unavailable, or how missing observations were handled. The named analysis population therefore clarifies who could contribute but does not establish that missingness had no effect.
The record does not specify the analysis population for the antibody objectives or the concurrent anti-poliovirus objectives. It also does not report whether analyses used all available measurements, a per-protocol subset, or another defined population. Interim analyses, stopping rules, and any pre-specified statistical analysis plan are not reported in the registry record. These omissions limit assessment of selective outcome reporting and of how closely the posted results, if available, would correspond to planned analyses.
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 |
|---|---|---|---|
| DAPTACEL®-Primed | 5 | 487 | 1.0% |
| Pentacel®-Primed | 3 | 162 | 1.9% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5.0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| DAPTACEL®-Primed | 62 of 487 |
| Pentacel®-Primed | 55 of 162 |
Most frequent serious adverse event terms
| Event term | Organ system | DAPTACEL®-Primed | Pentacel®-Primed |
|---|---|---|---|
| Gastroenteritis NOS | Infections and infestations | 0 of 487 | 2 of 162 |
| Asthma NOS | Skin and subcutaneous tissue disorders | 2 of 487 | 0 of 162 |
| Thrombocytopenic purpura | Blood and lymphatic system disorders | 0 of 487 | 1 of 162 |
| Supraventricular tachycardia | Cardiac disorders | 0 of 487 | 1 of 162 |
| Otitis media NOS | Infections and infestations | 1 of 487 | 0 of 162 |
| Pneumonia respiratory syncytial viral | Infections and infestations | 1 of 487 | 0 of 162 |
| Head injury | Injury, poisoning and procedural complications | 1 of 487 | 0 of 162 |
| Skull fracture NOS | Injury, poisoning and procedural complications | 1 of 487 | 0 of 162 |
| Dehydration | Metabolism and nutrition disorders | 0 of 487 | 1 of 162 |
| Staring | Psychiatric disorders | 1 of 487 | 0 of 162 |
Most frequent non-serious adverse event terms
| Event term | Organ system | DAPTACEL®-Primed | Pentacel®-Primed |
|---|---|---|---|
| Injection site tenderness | General disorders | 62 of 487 | 55 of 162 |
| Irritability | Psychiatric disorders | 36 of 487 | 28 of 162 |
| Injection site redness | General disorders | 36 of 487 | 24 of 162 |
| Upper respiratory tract infection NOS | Infections and infestations | 34 of 487 | 7 of 162 |
| Lethargy | Gastrointestinal disorders | 22 of 487 | 17 of 162 |
| Injection site swelling | General disorders | 24 of 487 | 14 of 162 |
| Otitis media NOS | Infections and infestations | 24 of 487 | 9 of 162 |
| Anorexia | Musculoskeletal and connective tissue disorders | 16 of 487 | 14 of 162 |
| Crying | Psychiatric disorders | 15 of 487 | 11 of 162 |
Serious events with the highest arm-level rate: gastroenteritis nos (1.2%), thrombocytopenic purpura (0.6%), supraventricular tachycardia (0.6%), dehydration (0.6%), asthma nos (0.4%).
The serious adverse-event figures are reported separately for the prior-vaccination groups. The DAPTACEL®-Primed group has 5 affected participants among 487 at risk; the Pentacel®-Primed group has 3 affected participants among 162 at risk. Other adverse-event counts are 62 among 487 and 55 among 162, respectively. These are descriptive figures and should not be interpreted as a causal comparison between groups.
The listed serious-event terms and percentages are Gastroenteritis NOS, 1.2%; Thrombocytopenic purpura, 0.6%; Supraventricular tachycardia, 0.6%; Dehydration, 0.6%; Asthma NOS, 0.4%; and Otitis media NOS, 0.2%. These percentages are presented as recorded; the registry record does not explain their calculation or provide uncertainty intervals for them.
Serious adverse events are not necessarily caused by the study vaccination. The record does not report an attribution assessment for the listed events. Death figures are not reported in the registry record. The serious-event summaries also do not replace the primary endpoint, which concerns solicited reactions during 0 to 7 days after vaccination; its numerical result is not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The record establishes that the study examined safety and antibody-response objectives after a fifth DAPTACEL® dose in children aged 4 to 6 years with different prior-vaccination histories. It also records serious and other adverse-event counts for the two groups. Those details describe the study and selected safety observations; they do not, by themselves, establish a treatment effect.
The primary endpoint is the percentage reporting solicited local or systemic reactions during 0 to 7 days after the fifth dose. Its numerical result is not reported in the registry record. Without the endpoint estimate and its precision, the frequency of those reactions cannot be quantified from the posted primary-outcome information. The numerical antibody results are also not reported, so the size and precision of antibody responses cannot be evaluated.
The antibody objective mentions equivalence criteria, but equivalence is a conclusion based on pre-specified margins and suitable results, not simply an intention to compare groups. The registry record does not report the margins or the analysis results. It therefore does not establish that antibody responses were equivalent.
Because the groups were non-randomized, comparisons between them are vulnerable to baseline differences. The safety counts cannot establish that one prior-vaccination history led to more or fewer events, and they cannot establish that DAPTACEL® caused any event. The record also does not provide a randomized comparison with an unvaccinated group.
As a general statistical principle, estimates should be read alongside their uncertainty, the population analyzed, and the design that generated the data. Here, key outcome estimates and analysis details are absent. The results described in the registry record are therefore limited evidence about the stated objectives rather than a complete basis for judging effect size, precision, equivalence, or causality.
13. Why This Trial Matters Statistically
This study raises several useful statistical issues for clinical research. First, its two groups are defined by previous vaccination rather than randomized assignment. That design distinction affects what can be concluded from a group comparison: observed differences may reflect baseline characteristics as well as outcomes associated with prior vaccine history.
Second, the primary endpoint is a short-window binary safety outcome. Such an endpoint can be summarized as a percentage, but interpretation requires clear event definitions, an explicit denominator, and information about missing reaction reports. The record identifies the observation period and analysis population but does not report the primary endpoint result or the amount of missing reaction data.
Third, the record includes both descriptive safety aims and antibody-response objectives, including an equivalence objective. Equivalence questions require pre-specified margins and estimates precise enough to assess those margins. The objective alone cannot demonstrate equivalence. This distinction is important because a failure to identify a difference and evidence that differences are acceptably small are not the same statistical conclusion.
Finally, the posted adverse-event counts illustrate why descriptive figures need context. Counts by group do not account for non-randomized group formation, provide uncertainty by themselves, or establish causation. A complete statistical interpretation would require outcome estimates, analysis methods, missing-data information, and the planned handling of multiple objectives. Several of these details are not reported in the registry record.
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 for interpreting the primary outcome is that its numerical result is not reported in the registry record. The record gives the endpoint definition and observation period, but not the event counts, percentage estimate, or interval quantifying precision. The listed antibody objectives likewise lack numerical results.
The comparison groups were not randomized. Their earlier vaccination histories define group membership, so the groups may differ in other ways. The registry record does not report adjustment methods or information sufficient to assess whether potential confounding was addressed. The lack of masking is also recorded; the potential relevance of knowledge of treatment depends on the outcome and assessment process, details not reported in the registry record.
The primary safety population is described as enrolled and vaccinated participants with available reaction data. The record does not give the number with unavailable data, explain why data were missing, or describe a missing-data strategy. It also does not report the analysis population for each antibody objective.
The record does not provide solicited-reaction definitions, the equivalence margins, statistical models, confidence intervals, or p-values for the objectives. It does not report a multiplicity strategy, interim analyses, or a statistical analysis plan. The serious-event counts and term percentages are descriptive information, with no reported statistical comparison or event-attribution details. These gaps limit conclusions about effect size, precision, equivalence, and causation.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Safety and Immunogenicity of DAPTACEL® as 5th Dose in Children 4 to 6 Years Old After 4 Doses of Pentacel™ or DAPTACEL® — NCT00258895.
- Registry record last updated 2016-04-14; status last verified 2016-04.
- Results first posted 2009-09-28.
- 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
NCT00258895 is a completed phase 3, parallel-group study with non-randomized allocation and no masking listed. It enrolled 649 children aged 4 to 6 years who had received 4 earlier doses of DAPTACEL® or Pentacel™, and examined a fifth DAPTACEL® dose. The recorded study start is 2005-03, with primary completion in 2006-12. Sanofi Pasteur, a Sanofi Company, is listed as sponsor.
The primary endpoint concerns solicited local or systemic reactions during 0 to 7 days after vaccination. Its numerical result and the antibody-response results are not reported in the registry record. Serious and other adverse-event counts are reported by prior-vaccination group, but no causal or adjusted comparison is reported. The observational design and incomplete outcome and analysis details limit statistical interpretation.