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 Study for Use of Menactra® Versus Adacel® in Subjects 11 to 55 Years of Age in South Korea (NCT01642589), a randomized phase 3 study. The primary outcome is Percentage of Participants With Seroconversion Following Vaccination With Either Menactra® or Adacel® Vaccine.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01642589 |
| Phase | Phase 3 |
| Condition | Meningitis, Meningococcal Disease |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 300 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sanofi Pasteur, a Sanofi Company |
| Results posted | Yes |
2. Clinical Question
Population
Participants aged 11 to 55 years in South Korea. The study record gives an enrollment of 300 and states that the primary outcome population was the Full Analysis Set.
Intervention
A single dose of Menactra®, a meningococcal groups A, C, Y and W-135 polysaccharide diphtheria toxoid conjugate vaccine.
Comparator
A single dose of Adacel®, a tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine adsorbed.
Primary question
At 28 days post-vaccination, what percentage of participants had seroconversion, defined as a post-vaccination antibody titer at least a 4-fold increase from the pre-vaccination level? The stated primary objective was to show a seroconversion rate higher than 60% for each of serogroups A, C, Y and W-135 after Menactra®. A secondary objective was to compare seroconversion rates between Menactra® and Adacel®.
The registry record presents the study as an assessment of safety and immunogenicity to support registration of Menactra® in South Korea. Immunogenicity refers to the immune response measured in the study; it is not itself a report of clinical disease prevention. The listed primary outcome title refers to participants with seroconversion following either vaccine, while the stated primary objective specifically concerns the Menactra® response against a threshold. The registry record does not provide outcome values that would answer either question.
3. Trial Design
The study is listed as phase 3, randomized, single-masked and parallel-group. In a randomized study, assignment is intended to allocate participants to study groups by chance rather than by clinical choice. A parallel-group design means that participants are assigned to one vaccine group for the comparison. The record identifies the groups as Menactra® and Tdap - Adacel®.
The study enrolled 300 participants. Its title describes participants aged 11 to 55 years in South Korea. The reported study dates are 2012-07 for the start and 2013-01 for primary completion; the status is completed. The record does not give further details about the recruitment sites or the methods used to generate or conceal the random allocation.
Masking is recorded as single, but the record does not say which people were masked or describe how masking was maintained. It therefore does not establish whether participants, investigators, outcome assessors, or another group were unaware of vaccine assignment. These details matter because knowledge of assignment can influence how symptoms are reported, assessed, or recorded.
Both interventions are described as biological products, and the study objectives refer to a single dose of either vaccine. The primary outcome was assessed 28 days post-vaccination. Secondary outcomes include functional antibody titers before and after vaccination, geometric mean titers measured by SBA-BR, and solicited injection-site and systemic events. The record does not specify the full schedule for each secondary assessment or the methods used to collect safety events.
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 300 participants that met all inclusion but none of the exclusion criteria were randomized and vaccinated in this study
Overall Study
| Stage | Menactra® Group | Tdap - Adacel® Group |
|---|---|---|
| STARTED | 200 | 100 |
| COMPLETED | 199 | 99 |
| NOT COMPLETED | 1 | 1 |
Reasons for not completing this period:
| Reason | Menactra® Group | Tdap - Adacel® Group |
|---|---|---|
| Withdrawal by Subject | 1 | 1 |
Analysis population for the primary outcome, as defined in the registry: Functional antibody activity for anti meningococcal antibody to serogroups A, C, Y, and W 135 were determined in the Full 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 | Menactra® Group | Tdap - Adacel® Group | Total |
|---|---|---|---|---|
| Participants analysed | 200 | 100 | 300 | |
| Age, Categorical: <=18 years | Participants | 100 | 49 | 149 |
| Age, Categorical: Between 18 and 65 years | Participants | 100 | 51 | 151 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Age Continuous | Years | 24.9 (SD 11.5) | 24.2 (SD 10.1) | 24.7 (SD 11.0) |
| Sex: Female, Male: Female | Participants | 107 | 58 | 165 |
| Sex: Female, Male: Male | Participants | 93 | 42 | 135 |
| Region of Enrollment: Korea, Republic of | Participants | 200 | 100 | 300 |
6. Primary Endpoint
The registry lists the primary outcome as Percentage of Participants With Seroconversion Following Vaccination With Either Menactra® or Adacel® Vaccine, measured over 28 Days post-vaccination.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Percentage of participants |
| Endpoint classification | Binary Endpoint |
The primary outcome is the percentage of participants with seroconversion following vaccination with either Menactra® or Adacel®. The measurement is based on functional anti-meningococcal antibody activity against serogroups A, C, Y and W-135, assessed using the Serum bactericidal assay using baby rabbit complement (SBA-BR). The stated time point is 28 days post-vaccination.
Seroconversion is defined in the registry record as a post-vaccination antibody titer at least a 4-fold increase from the pre-vaccination level. This definition focuses on change from each participant’s baseline rather than on a single post-vaccination level. The study’s primary objective further specifies a target of a seroconversion rate higher than 60% for each of the four serogroups after Menactra®. A secondary objective is to compare the rate between Menactra® and Adacel®.
In general, an antibody response endpoint is used to describe immune activity measured in laboratory assays. It can address whether the measured antibody response changed after vaccination, but it does not by itself report a clinical outcome such as meningococcal illness. The registry record identifies the Full Analysis Set as the population in which functional antibody activity was determined. It does not report the seroconversion counts or percentages, or the corresponding results for the individual serogroups.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the primary outcome and its definition, but it does not report a result for seroconversion. It gives no participant counts, percentages, uncertainty intervals, or statistical test results for serogroups A, C, Y or W-135. Consequently, the stated objective of assessing whether the Menactra® seroconversion rate was higher than 60% cannot be evaluated from the record’s posted results. The secondary objective comparing seroconversion between the vaccines also cannot be evaluated.
This distinction is important: an objective is a question the study set out to address, not evidence of the answer. The stated aim to demonstrate a rate higher than a threshold does not establish that the threshold was met. Nor does the listing of a randomized comparison establish that one group had a higher response. Without the outcome estimates and their uncertainty, the direction and precision of any observed difference are unknown.
The safety figures are descriptive counts. The record lists zero participants with serious adverse events among 200 at risk in the Menactra® group and zero among 100 at risk in the Tdap - Adacel® group. It also lists 92 and 76 participants, respectively, with other adverse events. These categories are not defined in the record, and the figures do not include descriptions of event type, severity, timing, or duration. The listed serious-event terms contain no entries; deaths are not reported in the record. These counts should not be treated as a complete account of safety or as evidence that no unrecorded events occurred.
In general, estimates from a trial are interpreted together with their precision. A confidence interval describes a range of values compatible with the data under the statistical method used; a narrow interval indicates greater precision than a wide one. No confidence intervals or other measures of uncertainty for the primary outcome are reported in the registry record. Thus, even the precision of a possible response estimate cannot be assessed.
The record states that there were five outcome measures and zero analysis entries. It does not report the analysis results needed to assess the primary objective, the between-vaccine comparison, or the secondary antibody outcomes. The available information therefore supports a description of the study question, design, endpoint definition and selected safety counts, but not a conclusion about the observed immunogenicity comparison.
9. Statistical Methods Explained
Statistical interpretation depends on separating the study question, the endpoint definition, the population included in analysis, and the actual results. The registry record describes each of the first three to some extent, but does not report primary outcome estimates or analysis results. The explanations below describe general statistical concepts; they are not claims about methods used in this trial unless the registry record explicitly says so.
What does a percentage endpoint represent?
The primary outcome is a percentage of participants meeting a binary definition: a participant either meets the seroconversion criterion or does not. In general, a percentage describes the proportion of an analysis population meeting that definition. To interpret it fully, readers need the number meeting the criterion, the number assessed, and the treatment of participants with missing measurements. The registry record does not report those primary outcome counts or the missing-data approach.
The endpoint is defined by a fold increase from a participant’s pre-vaccination antibody titer to the post-vaccination titer. This makes the baseline measurement part of the classification. In general, assay measurement variability and values near a decision threshold can affect whether a participant is classified as meeting a binary criterion. The record states the seroconversion definition and assay, but does not describe assay variability, laboratory procedures, or any handling of results that could not be measured.
How should the threshold objective be understood?
The primary objective is framed as demonstrating a seroconversion rate higher than 60% for serogroups A, C, Y and W-135 after Menactra®. In general, a threshold objective is assessed by comparing an estimated response rate with the specified threshold while accounting for uncertainty. A point estimate alone may not show how precisely the response rate is known. The registry record does not report a test, confidence interval, or other inferential result for this objective, so the statistical criterion used to judge it is not reported in the registry record.
The objective also concerns several serogroups. In general, when conclusions are drawn across multiple endpoints or groups, the chance of at least one misleading positive finding can increase if each is tested separately without a plan for multiplicity. A prespecified approach can define which outcomes are primary, how comparisons are ordered, or how error rates are controlled. The registry record does not report a multiplicity strategy or the statistical analysis plan.
What does the vaccine comparison require?
The secondary objective compares seroconversion rates for Menactra® and Adacel®. In general, a treatment comparison should be interpreted using an effect estimate and its uncertainty, rather than by looking only at whether each group separately meets a threshold. The registry record does not report group-specific seroconversion results or a between-group estimate. It also does not report whether the comparison was adjusted for any covariates or how the analysis handled the several serogroups.
Random allocation can reduce systematic differences between groups at study entry, on average, when implemented and analyzed appropriately. It does not remove random variation, prevent missing outcome data, or guarantee that the groups are identical in every characteristic. The record identifies the study as randomized but does not describe the allocation sequence, concealment, analysis model, or baseline characteristics relevant to the outcome.
What is the role of antibody titer summaries?
The secondary outcomes include functional antibody titers at ≥1:8 and ≥1:128 dilutions and geometric mean titers from SBA-BR before and after vaccination. In general, geometric means summarize measurements on a multiplicative scale and are often used when values are positively skewed. They do not have the same interpretation as a percentage of participants meeting a binary response definition. The registry record lists these measures but does not report their results or the methods used to calculate or compare them.
What can be inferred about power and sample size?
The registry record gives an enrollment of 300. It does not report the study’s sample-size justification or planned power calculation. A sample-size calculation depends on assumptions about the outcome, target effect, variability, allocation and analysis method; without those details, enrollment alone does not establish how precisely the primary outcome could be estimated.
In general, a planning illustration based on an observed effect is not an estimate of observed power and does not replace a study’s prospective design justification. The record does not report analysis results from which to assess the observed effect. Any power or sample-size interpretation beyond the stated enrollment and objectives is therefore not supported by the registry record.
Why are uncertainty and analysis details important?
A confidence interval communicates the range of values reasonably compatible with an estimate under a stated method. A p-value, when used, describes how unusual data at least as inconsistent with a specified null hypothesis would be under that hypothesis and the model assumptions. Neither measure supplies the magnitude or clinical importance of an effect by itself. No confidence intervals, p-values, model specifications, or detailed statistical methods for the primary outcome are reported in the registry record.
For a binary endpoint, the analysis also needs to account for the participants eligible for evaluation and those with unavailable measurements. Different choices can change the denominator and the interpretation of the resulting percentage. The record identifies the Full Analysis Set for determining antibody activity, but does not define its membership or report how exclusions and missing measurements were handled. These omissions limit independent assessment of the endpoint analysis.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists one primary outcome and four secondary outcome descriptions, for five outcome measures in total. The primary objective names four serogroups, and the secondary objectives include both a comparison between vaccines and several antibody measures. When multiple outcomes or groups are considered, multiplicity can affect how confidently a positive result is interpreted. In general, a prespecified testing hierarchy or adjustment can address this issue. The statistical plan and any multiplicity procedure are not reported in the registry record.
The record identifies the Full Analysis Set as the population used to determine functional antibody activity. It does not define the set, explain whether participants were analyzed according to randomized assignment, or specify the analysis population for every endpoint. The approach to missing pre-vaccination or post-vaccination antibody measurements is not reported in the registry record. Nor are the numbers of participants with evaluable measurements reported for each serogroup.
Missing outcomes can reduce precision and can also affect interpretation if the reasons for missingness differ between groups or relate to response. In general, analysis choices may include excluding participants without a measurement, using a prespecified imputation approach, or conducting sensitivity analyses; these approaches rely on different assumptions. No such approach is reported for this study. The registry record also does not report interim analyses, a detailed analysis plan, or a sample-size justification.
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 |
|---|---|---|---|
| Menactra® Group | 0 | 200 | 0.0% |
| Tdap - Adacel® Group | 0 | 100 | 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 |
|---|---|
| Menactra® Group | 92 of 200 |
| Tdap - Adacel® Group | 76 of 100 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Menactra® Group | Tdap - Adacel® Group |
|---|---|---|---|
| Injection Site Pain | General disorders | 64 of 199 | 72 of 99 |
| Myalgia | Musculoskeletal and connective tissue disorders | 51 of 199 | 42 of 99 |
| Headache | Nervous system disorders | 37 of 199 | 24 of 99 |
| Malaise | General disorders | 36 of 199 | 23 of 99 |
| Injection Site Erythema | General disorders | 5 of 199 | 9 of 99 |
| Injection Site Swelling | General disorders | 3 of 199 | 6 of 99 |
The registry record lists serious adverse events for 200 participants at risk in the Menactra® group and 100 in the Tdap - Adacel® group. The number affected is recorded as zero in each group. This is a reported count, not a statement that every possible safety outcome was measured or that no events occurred outside the recorded category. The serious adverse event terms list contains no entries, and deaths are not reported in the registry record.
For other adverse events, the record lists 92 participants affected among 200 at risk in the Menactra® group and 76 among 100 at risk in the Tdap - Adacel® group. It does not define this “other” category, identify the events, or state the observation period or severity criteria. The counts therefore cannot be used to compare particular symptoms or to determine their timing, duration, or seriousness. No additional rates or comparisons are calculated.
In general, safety counts are most informative when accompanied by clear definitions, observation windows, event-level details, and the number of participants assessed. The record’s figures should be read as the posted counts for the categories identified, not as a complete safety profile.
12. What the Result Does, and Does Not, Mean
The registry record establishes what the investigators intended to measure: seroconversion after vaccination, with an objective concerning a rate higher than 60% for each of four meningococcal serogroups after Menactra®, and a secondary comparison with Adacel®. It also identifies the assay, the response definition, the assessment time point and the analysis population named for antibody activity. These details make the intended immunogenicity question understandable.
However, the registry record does not report the primary outcome values or statistical analyses. It therefore does not show whether the stated threshold objective was met, how seroconversion differed between the vaccine groups, or how precise any estimate was. Listing an objective is not the same as reporting its result. Likewise, a completed study status does not supply an outcome estimate.
Seroconversion is a laboratory antibody response measure. In general, an immunogenicity endpoint can describe immune activity under the assay and response definition used, but it is not itself a clinical endpoint. The record does not report clinical disease outcomes that would establish how the antibody findings relate to meningitis or meningococcal disease in this study population.
The safety counts provide limited descriptive information. Zero serious adverse events are recorded in both groups, while other adverse event counts are also listed. Without event definitions and details, the counts cannot characterize particular risks or establish a comparative safety profile. The absence of reported deaths is not equivalent to evidence about all possible safety outcomes.
Overall, the available record supports a clear description of the study design and planned immunogenicity questions, alongside selected safety counts. It does not support a conclusion about which vaccine produced a higher seroconversion rate, whether a threshold was achieved, or the degree of uncertainty around those outcomes.
13. Why This Trial Matters Statistically
This trial is statistically notable because its primary question is framed around a threshold response rate, while a secondary objective asks for a direct comparison between two vaccine groups. These are distinct inferential questions. A threshold objective asks whether a response rate exceeds a specified benchmark; a between-group objective asks how the response rates compare. Each requires the relevant estimates and uncertainty, neither of which is reported in the registry record.
The endpoint also involves four serogroups. A response may be defined separately for each, making clarity about the analysis plan and multiplicity important. The registry record states the seroconversion definition and names the groups, but does not report how the results were analyzed across them. This illustrates why identifying the endpoint alone is not enough to understand the strength of an inference.
The record’s naming of a Full Analysis Set is useful because analysis populations influence which participants contribute to an estimate. But the set is not defined, and missing-data handling is not described. These are not minor technical details: they determine the denominator and can affect the interpretation of a percentage endpoint.
Finally, the contrast between a specific immunogenicity objective and the absence of posted outcome estimates highlights the difference between a registry description and a results report. The design and endpoint definitions explain what was intended to be learned. Without results and measures of precision, they cannot establish what the study observed or how reliably the observations address the stated questions.
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 central limitation for interpreting this trial from the registry record is that primary outcome results are not reported. There are no seroconversion counts or percentages by group or serogroup, and no uncertainty estimates or statistical tests. The secondary immunogenicity results are also not reported. This prevents evaluation of the stated threshold objective and the vaccine comparison.
Some design details are limited. Although the study is recorded as randomized and single-masked, the allocation procedure and the identity of the masked parties are not reported in the registry record. The record does not give recruitment-site information, baseline characteristics, or details about how the single-dose intervention and outcome assessments were implemented.
The Full Analysis Set is named but not defined. The number of participants with evaluable antibody measurements, exclusions from each analysis, and the handling of missing data are not reported. The record also does not provide a statistical analysis plan, a multiplicity approach, interim analysis information, or a sample-size justification.
Safety interpretation is constrained by limited event descriptions. Serious adverse event counts and other adverse event counts are listed, but event definitions, individual terms, severity, timing and observation period are not reported. Deaths are not reported in the registry record. These limitations restrict what can be inferred from the posted safety figures.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Safety and Immunogenicity Study for Use of Menactra® Versus Adacel® in Subjects 11 to 55 Years of Age in South Korea — NCT01642589.
- Registry record last updated 2013-12-03; status last verified 2013-11.
- Results first posted 2013-12-03.
- 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
This completed phase 3 study was randomized, single-masked and parallel-group, with an enrollment of 300. It compared a single dose of Menactra® with a single dose of Tdap - Adacel® in participants aged 11 to 55 years in South Korea. The recorded study start was 2012-07 and primary completion was 2013-01.
The primary outcome was the percentage of participants with seroconversion at 28 days post-vaccination, defined by an antibody titer at least a 4-fold increase from pre-vaccination. The primary objective concerned a rate higher than 60% for serogroups A, C, Y and W-135 after Menactra®. Primary and secondary outcome results are not reported in the registry record.
The record lists zero serious adverse events in each group and other adverse events affecting 92 participants in the Menactra® group and 76 in the Tdap - Adacel® group. The event details are limited, so these counts do not establish a comparative safety profile.