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 Adsorbed in Healthy Subjects (NCT02587520), a randomized phase 1, phase 2 study. The primary outcome is Number of Participants With Solicited Injections Site or Systemic Reactions Following Vaccination at Day 0: Aged 10-18 Years.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02587520 |
| Phase | Phase 1, Phase 2 |
| Condition | Tetanus, Diphtheria, Pertussis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 1363 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sanofi Pasteur, a Sanofi Company |
| Results posted | Yes |
2. Clinical Question
Population
Healthy adolescents aged 10-18 years, adults aged 19-64 years, and older adults aged 65 years or older in the United States. The primary endpoint described in the registry record concerns adolescents.
Intervention
One of four investigational SP0173 Tdap formulations, each given as a single dose. The study was designed to examine different doses and formulations, although specific dose details are not reported in the registry record.
Comparator
Licensed Adacel® or Boostrix® Tdap vaccines. The registry lists these comparator arms within each of the three age groups.
Primary question
For adolescents, how many participants had at least one solicited injection-site or systemic reaction within 7 days after vaccination? The stated primary objective was to describe the safety profile of each investigational formulation; immunogenicity was an observational objective.
This is a dose- and formulation-ranging study rather than a single comparison of one experimental vaccine with one control. It includes four SP0173 formulations and two licensed vaccines, with arms in each age group. The registry identifies the safety outcome as a count of participants with reactions, not as a single comparative effect estimate. It does not report a prespecified hypothesis, a target difference between formulations, or a specific claim that one formulation should outperform another. Those details are not reported in the registry record.
The range of ages and formulations gives the study a descriptive focus: characterize reported safety and immunogenicity across the groups under study. The posted primary endpoint is limited to adolescents, while the adverse-event summaries also list adults and older adults. The registry record does not establish that the adolescent endpoint alone answers all safety questions for the other age groups.
3. Trial Design
The registry describes NCT02587520 as a randomized, quadruple-masked, parallel-group phase 1 and phase 2 study. Enrollment is listed as 1363. The study status is completed, with a start date of 2015-10-22 and primary completion date of 2017-02-21. The sponsor is Sanofi Pasteur, a Sanofi Company.
Healthy participants were enrolled in adolescent, adult, and older-adult groups. The age ranges are 10-18 years, 19-64 years, and 65 years or older, respectively. In each age group, the registry lists arms for four SP0173 Tdap formulations and the licensed vaccines Adacel® and Boostrix®. The arm descriptions state that SP0173 was administered as a single dose; the licensed-vaccine arm descriptions name the vaccine received. Specific doses and formulation contents are not reported in the registry record.
Random allocation is intended, in general, to reduce systematic differences between treatment groups at enrollment. Masking is intended to limit the influence of treatment knowledge on participants’ reports or study assessments. A parallel-group design assigns participants to a study arm rather than describing a crossover between vaccines. These are general features of the design; details of the randomization procedure, masking roles, and allocation concealment are not reported in the registry record.
The study’s stated primary objective was to describe safety for each investigational formulation. Its observational objective was to describe immunogenicity. The registry lists three outcome measures but no outcome-analysis entries. It does not report the protocol’s sample-size justification, interim analyses, or a detailed statistical analysis plan. The enrollment figure should therefore be read as the registry’s listed enrollment, not as evidence about the reasoning behind the planned study size.
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 1363 participants were randomized in a 1:1:1 ratio to 1 of the 6 formulation study groups. Randomization was stratified by age (adolescents: age 10-18 years, adults: age 19-64 years, and older adults: age greater than equal to \[\>=\] 65 years).
Only the first 6 of 18 groups are shown.
Overall Study
| Stage | Adolescents: SP0173 Formulation 1 | Adolescents: SP0173 Formulation 2 | Adolescents: SP0173 Formulation 3 | Adolescents: SP0173 Formulation 4 | Adolescents: Adacel® | Adolescents: Boostrix® |
|---|---|---|---|---|---|---|
| STARTED | 80 | 71 | 78 | 79 | 75 | 75 |
| Safety Analysis Set (SafAS) | 79 | 71 | 77 | 77 | 75 | 75 |
| COMPLETED | 78 | 69 | 77 | 74 | 75 | 72 |
| NOT COMPLETED | 2 | 2 | 1 | 5 | 0 | 3 |
Reasons for not completing this period:
| Reason | Adolescents: SP0173 Formulation 1 | Adolescents: SP0173 Formulation 2 | Adolescents: SP0173 Formulation 3 | Adolescents: SP0173 Formulation 4 | Adolescents: Adacel® | Adolescents: Boostrix® |
|---|---|---|---|---|---|---|
| Protocol Violation | 2 | 0 | 0 | 2 | 0 | 1 |
| Adverse Event | 0 | 0 | 0 | 0 | 0 | 0 |
| Withdrawal by Subject | 0 | 0 | 1 | 1 | 0 | 1 |
| Lost to Follow-up | 0 | 2 | 0 | 2 | 0 | 1 |
Analysis population for the primary outcome, as defined in the registry: Safety analysis set that was defined as those participants who had received study vaccine. All participants had their safety analyzed according to the vaccine they actually received. Here, "number analyzed"= number of participants with available data for each specified category.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
Population: Analysis was performed on all randomized participants.
Only the first 6 of 19 groups are shown.
| Characteristic | Unit | Adolescents: SP0173 Formulation 1 | Adolescents: SP0173 Formulation 2 | Adolescents: SP0173 Formulation 3 | Adolescents: SP0173 Formulation 4 | Adolescents: Adacel® | Adolescents: Boostrix® |
|---|---|---|---|---|---|---|---|
| Participants analysed | 80 | 71 | 78 | 79 | 75 | 75 | |
| Age, Continuous | years | 10.8 (SD 1.3) | 11.0 (SD 1.3) | 11.1 (SD 1.6) | 10.8 (SD 1.4) | 10.8 (SD 1.5) | 11.1 (SD 1.6) |
| Sex: Female, Male: Female | Participants | 41 | 33 | 35 | 37 | 39 | 40 |
| Sex: Female, Male: Male | Participants | 39 | 38 | 43 | 42 | 36 | 35 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 4 | 2 | 3 | 4 | 4 | 6 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 76 | 69 | 75 | 75 | 71 | 69 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 1 | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 1 | 0 | 2 | 2 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 1 | 1 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 7 | 9 | 2 | 4 | 8 | 4 |
| Race (NIH/OMB): White | Participants | 71 | 60 | 71 | 72 | 63 | 65 |
| Race (NIH/OMB): More than one race | Participants | 2 | 1 | 3 | 2 | 2 | 4 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 | 0 | 0 | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants With Solicited Injections Site or Systemic Reactions Following Vaccination at Day 0: Aged 10-18 Years, measured over Within 7 days after vaccination.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the number of participants aged 10-18 years with solicited injection-site or systemic reactions following vaccination at Day 0. The timeframe is within 7 days after vaccination. The registry defines a solicited reaction as an adverse event that was prelisted in the electronic case report form and reported under the specified symptom and onset conditions.
Listed injection-site reactions include pain, erythema, swelling, upper limb edema, and extensive limb swelling. Listed systemic reactions include fever, headache, malaise, and myalgia. The endpoint description says that participants with at least one solicited injection-site reaction and systemic reaction were reported. It is therefore a participant-count outcome, rather than a measure of reaction severity, duration, or average symptom burden.
Soliciting specific symptoms can make safety reporting more systematic: participants and investigators are prompted to report a defined set of events within a defined period. This is a general rationale for solicited outcomes. It also means the endpoint does not cover every possible adverse event; the registry distinguishes unsolicited events as those that do not meet the prespecified symptom or post-vaccination onset conditions.
The registry record does not give a single endpoint comparison or an effect estimate to interpret. The endpoint is described across multiple categories or time points rather than reduced to one comparison. The record also does not report the separate event counts for the primary endpoint in the material summarized by these results.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary safety question is descriptive: how many adolescents reported at least one solicited reaction within 7 days after vaccination, by vaccine arm? Although the endpoint is clearly defined, the registry record does not reduce the reported outcome to one comparison. It therefore does not support a single estimate of the difference between an SP0173 formulation and either licensed vaccine. The arm-level summaries for this endpoint are not reported in the registry record.
Other adverse-event summaries give counts of participants at risk and participants affected, separately for serious and other adverse events. These are descriptive counts. They do not, by themselves, establish that a vaccine caused an event or that apparent differences between arms are more than chance variation. The groups are split by age and vaccine arm, so interpretation should keep each age group and treatment assignment distinct rather than treating all arms as one comparison.
The serious-event counts are sparse in the listed arms, including arms with no affected participants and arms with one or more. Sparse counts contain limited information about comparative safety. In general, when an outcome is uncommon, a small change in the observed count can produce a large change in a relative summary; absolute counts and their denominators should remain visible. No comparative confidence intervals or adjusted estimates are reported in the registry record.
The registry lists serious-event terms including Ventricular Fibrillation, Transient Ischaemic Attack, Post-Traumatic Stress Disorder, Coronary Artery Disease, Humerus Fracture, and Asthma, each with a listed percentage of 1.4%. These terms are not a substitute for a complete account of all events, their timing, clinical context, or relationship to vaccination. Those details are not reported in the registry record.
No inference about immunogenicity can be drawn from these safety counts. Immunogenicity was an observational objective, but the corresponding results are not reported in the information. The posted evidence is therefore best read as a registry record of design, an adolescent solicited-reaction endpoint, and adverse-event counts, rather than as a complete comparative efficacy or safety analysis.
9. Statistical Methods Explained
The registry identifies a randomized, quadruple-masked, parallel-group trial. These design terms describe how the study was organized; they do not, on their own, establish that treatment groups were comparable in every respect or that every possible source of bias was removed. The details needed to assess the implementation of these methods are not reported in the registry record.
What does randomization contribute?
In general, random assignment is used to make treatment allocation less dependent on participant characteristics or investigator choice. If implemented successfully, it can support a fairer comparison of outcomes across arms. Chance differences can still occur, particularly within smaller groups, and randomization does not repair missing outcome data or measurement problems. The method used to generate the allocation sequence, any stratification factors, and the concealment process are not reported in the registry record.
What does masking mean for this study?
Quadruple masking indicates that the registry classifies the study as masked across four roles, but the roles and the practical masking procedures are not reported in the registry record. In general, masking can reduce the influence of knowledge about treatment assignment on symptom reporting, clinical assessment, or event classification. It cannot guarantee that participants or staff remain unaware of assignment, and it does not remove the need for clearly defined outcomes and consistent follow-up.
How should a participant count be read?
The primary endpoint is a binary participant-level outcome: a participant either had at least one qualifying solicited reaction during the specified period or did not. The registry describes the result as a number of participants, with the number analyzed defined as participants with available data for each specified category. In general, a count is most informative alongside its denominator. The registry’s adverse-event entries list participants at risk and participants affected for each arm. The primary endpoint’s arm-level counts and denominators are not reported in the registry record, so no rate or between-arm contrast should be inferred from the adverse-event entries.
Counts are not the same as event totals. One participant may have more than one reaction, but the primary endpoint counts participants with at least one qualifying reaction. The registry does not provide the number of individual reactions, severity distribution, or duration for the primary endpoint in the information. The adverse-event summaries should likewise be interpreted according to their stated participant-count presentation, not assumed to represent a count of every episode.
What can a confidence interval tell a reader?
In general, a confidence interval describes the uncertainty around an estimated quantity under the assumptions of the analysis. A wide interval indicates less precision than a narrow interval, while an interval around a comparative estimate can show which effect sizes remain compatible with the data. The registry record does not report confidence intervals or a comparative estimate for the primary endpoint. Accordingly, its precision cannot be judged from a single endpoint estimate, and the counts should not be treated as proof of equivalence or difference.
What do the planning illustrations represent?
The separate planning illustrations use a stated two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They use a fraction of an observed effect as the effect to detect. These are planning illustrations based on the observed effect, not the trial’s own design justification and not observed power. In general, a sample-size calculation estimates the participants needed under chosen assumptions; it does not show the probability that the completed trial has established an effect. The registry record does not report that these assumptions were used to design the trial.
No recalculated comparative result is reported in the registry record. There is therefore no recalculated estimate to set against a sponsor analysis. The registry lists three outcome measures and zero analysis entries; it does not report the model, covariates, test procedure, or adjustment strategy behind a formal comparative analysis. These omissions limit what can be concluded about statistical significance and precision.
Why does the analysis population matter?
The primary endpoint description defines the safety analysis set as participants who received study vaccine, with participants analyzed according to the vaccine actually received. This is a safety-population definition. In general, analyzing participants according to the vaccine received can be appropriate for describing exposure-related safety, but it is not the same as an intention-to-treat approach based on randomized assignment. The registry record does not describe an intention-to-treat analysis for this endpoint or give details about participants excluded from any analysis.
10. Multiplicity, Missing Data and Analysis Populations
This study includes multiple SP0173 formulations, two licensed vaccine comparators, three age groups, and several outcome measures. When many outcomes or comparisons are examined, the chance of finding an apparently unusual result by chance can increase. General approaches to address this issue include prespecifying a primary comparison, controlling a family-wise error rate, or treating results as exploratory. The registry record does not report a multiplicity strategy, a hierarchy of comparisons, or a detailed statistical analysis plan. It is therefore not possible to determine whether or how the study accounted for multiple comparisons.
The primary endpoint is described as involving several categories or time points, and the registry does not reduce it to one comparison. No single comparative estimate or associated uncertainty measure is reported in the registry record. This leaves no basis for interpreting a formal significance test or declaring that one formulation differs from another on this endpoint.
The safety analysis set includes participants who received study vaccine, analyzed according to the vaccine actually received. The registry defines the number analyzed as participants with available data for each specified category. This identifies the general analysis population, but does not explain how missing observations were handled, how much data were missing, or whether missingness differed across arms. These details are not reported in the registry record.
Missing data can affect interpretation when participants without recorded outcomes differ from those with available outcomes. In general, complete-case summaries describe those with available measurements and may not represent all randomized participants if missingness is informative. The registry record does not provide enough information to assess that possibility for the primary endpoint or immunogenicity outcomes.
Interim analyses, stopping rules, and a sample-size justification are also not reported in the registry record. Their absence from the record does not establish whether such procedures were or were not used; it means their use cannot be assessed from the registered information.
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 |
|---|---|---|---|
| Adolescents: SP0173 Formulation 1 | 0 | 79 | 0.0% |
| Adolescents: SP0173 Formulation 2 | 0 | 71 | 0.0% |
| Adolescents: SP0173 Formulation 3 | 0 | 77 | 0.0% |
| Adolescents: SP0173 Formulation 4 | 1 | 77 | 1.3% |
| Adolescents: Adacel® | 0 | 75 | 0.0% |
| Adolescents: Boostrix® | 0 | 75 | 0.0% |
| Adults: SP0173 Formulation 1 | 1 | 76 | 1.3% |
| Adults: SP0173 Formulation 2 | 1 | 73 | 1.4% |
| Adults: SP0173 Formulation 3 | 1 | 76 | 1.3% |
| Adults: SP0173 Formulation 4 | 1 | 76 | 1.3% |
| Adults: Adacel® | 0 | 76 | 0.0% |
| Adults: Boostrix® | 2 | 72 | 2.8% |
| Older Adults: SP0173 Formulation 1 | 0 | 77 | 0.0% |
| Older Adults: SP0173 Formulation 2 | 3 | 73 | 4.1% |
| Older Adults: SP0173 Formulation 3 | 4 | 78 | 5.1% |
| Older Adults: SP0173 Formulation 4 | 1 | 72 | 1.4% |
| Older Adults: Adacel® | 2 | 76 | 2.6% |
| Older Adults: Boostrix® | 2 | 78 | 2.6% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Adolescents: SP0173 Formulation 1 | 0 of 79 |
| Adolescents: SP0173 Formulation 2 | 0 of 71 |
| Adolescents: SP0173 Formulation 3 | 0 of 77 |
| Adolescents: SP0173 Formulation 4 | 0 of 77 |
| Adolescents: Adacel® | 0 of 75 |
| Adolescents: Boostrix® | 0 of 75 |
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 |
|---|---|
| Adolescents: SP0173 Formulation 1 | 71 of 79 |
| Adolescents: SP0173 Formulation 2 | 64 of 71 |
| Adolescents: SP0173 Formulation 3 | 67 of 77 |
| Adolescents: SP0173 Formulation 4 | 68 of 77 |
| Adolescents: Adacel® | 71 of 75 |
| Adolescents: Boostrix® | 66 of 75 |
Most frequent serious adverse event terms
| Event term | Organ system | Adolescents: SP0173 Formulation 1 | Adolescents: SP0173 Formulation 2 | Adolescents: SP0173 Formulation 3 | Adolescents: SP0173 Formulation 4 | Adolescents: Adacel® | Adolescents: Boostrix® |
|---|---|---|---|---|---|---|---|
| Laceration | Injury, poisoning and procedural complications | 0 of 79 | 0 of 71 | 0 of 77 | 1 of 77 | 0 of 75 | 0 of 75 |
| Cardiac Failure Congestive | Cardiac disorders | 0 of 79 | 0 of 71 | 0 of 77 | 0 of 77 | 0 of 75 | 0 of 75 |
| Coronary Artery Disease | Cardiac disorders | 0 of 79 | 0 of 71 | 0 of 77 | 0 of 77 | 0 of 75 | 0 of 75 |
| Ventricular Fibrillation | Cardiac disorders | 0 of 79 | 0 of 71 | 0 of 77 | 0 of 77 | 0 of 75 | 0 of 75 |
| Device Dislocation | General disorders | 0 of 79 | 0 of 71 | 0 of 77 | 0 of 77 | 0 of 75 | 0 of 75 |
| Drug Withdrawal Syndrome | General disorders | 0 of 79 | 0 of 71 | 0 of 77 | 0 of 77 | 0 of 75 | 0 of 75 |
| Non-Cardiac Chest Pain | General disorders | 0 of 79 | 0 of 71 | 0 of 77 | 0 of 77 | 0 of 75 | 0 of 75 |
| Drug Hypersensitivity | Immune system disorders | 0 of 79 | 0 of 71 | 0 of 77 | 0 of 77 | 0 of 75 | 0 of 75 |
| Appendicitis Perforated | Infections and infestations | 0 of 79 | 0 of 71 | 0 of 77 | 0 of 77 | 0 of 75 | 0 of 75 |
| Pneumonia | Infections and infestations | 0 of 79 | 0 of 71 | 0 of 77 | 0 of 77 | 0 of 75 | 0 of 75 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Adolescents: SP0173 Formulation 1 | Adolescents: SP0173 Formulation 2 | Adolescents: SP0173 Formulation 3 | Adolescents: SP0173 Formulation 4 | Adolescents: Adacel® | Adolescents: Boostrix® |
|---|---|---|---|---|---|---|---|
| Injection Site Pain | General disorders | 59 of 79 | 51 of 71 | 50 of 77 | 49 of 77 | 59 of 75 | 48 of 75 |
| Change In Limb Circumference | General disorders | 45 of 79 | 41 of 71 | 49 of 77 | 46 of 77 | 48 of 75 | 33 of 75 |
| Myalgia | Musculoskeletal and connective tissue disorders | 42 of 79 | 35 of 71 | 38 of 77 | 42 of 77 | 52 of 75 | 38 of 75 |
| Headache | Nervous system disorders | 23 of 79 | 15 of 71 | 19 of 77 | 25 of 77 | 22 of 75 | 29 of 75 |
| Malaise | General disorders | 14 of 79 | 17 of 71 | 14 of 77 | 18 of 77 | 12 of 75 | 17 of 75 |
| Injection Site Erythema | General disorders | 9 of 79 | 4 of 71 | 10 of 77 | 1 of 77 | 4 of 75 | 2 of 75 |
| Pharyngitis Streptococcal | Infections and infestations | 5 of 79 | 4 of 71 | 5 of 77 | 5 of 77 | 2 of 75 | 4 of 75 |
| Injection Site Swelling | General disorders | 7 of 79 | 4 of 71 | 8 of 77 | 0 of 77 | 1 of 75 | 4 of 75 |
| Pharyngitis | Infections and infestations | 3 of 79 | 7 of 71 | 3 of 77 | 5 of 77 | 3 of 75 | 2 of 75 |
| Abdominal Pain | Gastrointestinal disorders | 3 of 79 | 3 of 71 | 4 of 77 | 1 of 77 | 3 of 75 | 1 of 75 |
Serious events with the highest arm-level rate: ventricular fibrillation (1.4%), transient ischaemic attack (1.4%), post-traumatic stress disorder (1.4%), coronary artery disease (1.4%), humerus fracture (1.4%).
The adverse-event summaries distinguish participants at risk from participants affected by serious adverse events and other adverse events. Read each count within its named vaccine arm and age group. For example, the serious-event affected count is 1 in Adolescents: SP0173 Formulation 4; it is 1 in each of Adults: SP0173 Formulations 1, 2, 3, and 4, and 2 in Adults: Boostrix®. Among older adults, the listed serious-event affected counts include 3 for SP0173 Formulation 2, 4 for SP0173 Formulation 3, 1 for SP0173 Formulation 4, and 2 each for Adacel® and Boostrix®. The other arms have their own counts in the adverse-event summaries.
The death count is 1 in Adults: Boostrix® and 0 in each other listed arm. These are counts, not evidence of causation. In general, an event occurring after vaccination is not necessarily caused by vaccination; assessing a relationship requires clinical context and a prespecified assessment process. The registry record does not report those details for the listed events.
Serious adverse-event terms are listed with percentages of 1.4%. The registry does not provide enough context to interpret those percentages as comparative rates across arms. Sparse counts should be read descriptively, with attention to each arm’s denominator and the limits of the available event details.
12. What the Result Does, and Does Not, Mean
The record describes a randomized study that examined four SP0173 Tdap formulations and two licensed vaccines in healthy adolescents, adults, and older adults. Its stated primary objective was to describe safety, with an observational objective to describe immunogenicity. The adolescent primary endpoint focused on solicited injection-site and systemic reactions within 7 days after vaccination.
The posted information does not provide one comparative result for that primary endpoint. It does not report an estimated difference between an SP0173 formulation and a licensed vaccine, a confidence interval for such a difference, or an adjusted analysis. Consequently, the record cannot establish whether the formulations differ on the endpoint or how precisely any difference has been estimated. The registry’s adverse-event counts offer descriptive safety information by age group and arm but do not resolve those comparative questions.
The counts also do not establish causation. Events observed after vaccination may have other explanations, and the registry record does not report the clinical context or relationship assessment needed to evaluate particular events. Nor do the safety summaries answer the immunogenicity objective; results for that objective are not reported in the information.
These limits should not be turned into a conclusion that there was no effect, no difference, or no safety concern. A missing comparative estimate is not evidence of equivalence. Likewise, sparse counts do not prove that rare events cannot occur. The conclusions supported by the record are narrower: the study design and objectives are documented, a specific adolescent solicited-reaction endpoint is defined, and adverse-event counts are listed across the trial arms. Stronger claims require analyses and outcome details not reported in the registry record.
13. Why This Trial Matters Statistically
This trial illustrates why a clear endpoint definition is only one part of interpreting a clinical study. The registry specifies the population, reaction types, and observation period for its primary safety endpoint. Yet without a single comparative estimate and a measure of its precision, readers cannot assess the size or uncertainty of a difference between vaccine arms. A well-defined outcome does not by itself answer a comparative question.
The design also creates an interpretive challenge: several formulations, licensed comparators, and age groups are represented. Such breadth can support descriptive comparisons across groups, but it also creates multiple possible contrasts. Without a reported analysis plan and multiplicity approach, readers cannot tell which comparisons were intended to carry confirmatory weight. General statistical practice distinguishes planned primary comparisons from exploratory contrasts; the registry record does not make that distinction clear.
Safety counts are important, but uncommon events are difficult to characterize precisely from sparse observations. Counts should be read with their denominators and event definitions, while avoiding claims that a count difference demonstrates a treatment effect. The listed serious-event terms further show why descriptive event reporting needs context, including timing, clinical details, and relatedness assessment.
The record is therefore useful for understanding the study’s structure and the kinds of safety outcomes it sought to describe. It also demonstrates the limits of registry-level summaries when comparative estimates, uncertainty measures, missing-data handling, and immunogenicity findings are not reported. For biostatistical interpretation, those omissions are material: they constrain what can be said about precision, multiplicity, and the evidence for between-arm differences.
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 endpoint is limited to solicited reactions among adolescents and within the stated 7-day period. It does not encompass all possible adverse events or describe longer-term safety. The endpoint is also described across multiple categories or time points without one consolidated comparative estimate. The registry record does not report the endpoint’s arm-level counts in the information.
Although adverse-event counts are listed for all age groups, the registry record does not provide comparative confidence intervals, adjusted estimates, or a detailed analysis plan. Counts alone do not account for chance variation or establish that a difference between arms reflects a vaccine effect. The multiple arms and age groups make clear prespecification and multiplicity handling relevant, but those methods are not reported.
The record gives a safety analysis-set definition based on participants who received study vaccine and were analyzed according to the vaccine actually received. It does not describe missing-data handling or provide information about the extent or pattern of missing observations. Randomization details, masking procedures, and the sample-size justification are also not reported in the registry record.
The listed serious adverse-event terms and percentages lack clinical detail in the information. Timing, event-level context, relatedness assessments, and comparative rates are not reported. The record also does not report immunogenicity results, despite identifying immunogenicity as an observational objective. These limitations mean the registry summary supports a description of the study and selected counts, but not a complete comparative assessment of safety or immune response.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of Tetanus Toxoid, Reduced Diphtheria Toxoid, and Acellular Pertussis Vaccine Adsorbed in Healthy Subjects — NCT02587520.
- Registry record last updated 2022-03-23; status last verified 2022-03.
- Results first posted 2020-03-04.
- 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
NCT02587520 is listed as a completed randomized, quadruple-masked, parallel-group phase 1 and phase 2 study sponsored by Sanofi Pasteur, a Sanofi Company. Enrollment is listed as 1363, with a start date of 2015-10-22 and primary completion date of 2017-02-21.
The study included healthy participants aged 10-18 years, 19-64 years, and 65 years or older. Arms included four SP0173 Tdap formulations and the licensed vaccines Adacel® and Boostrix®. The primary objective was to describe safety; the observational objective was to describe immunogenicity.
The primary endpoint describes solicited injection-site or systemic reactions among adolescents within 7 days after vaccination. The registry also lists serious and other adverse-event counts by arm. A single comparative estimate for the primary endpoint, detailed analysis methods, missing-data handling, and immunogenicity results are not reported in the registry record.