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 A Study of Meningococcal Vaccine, Menactra® in Healthy Subjects in India (NCT01086969), a non-randomized phase 3 study. The primary outcome is Number of Participants With Vaccine Antibody Titers at ≥ 8 Before and After Menactra Vaccination.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01086969 |
| Phase | Phase 3 |
| Condition | Meningococcal Infection, Meningitis |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 300 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sanofi |
| Results posted | Yes |
2. Clinical Question
Population
Healthy subjects in India, enrolled in age cohorts of 2 to 11 years, 12 to 17 years, and 18 to 55 years. The registry record lists enrollment of 300. The antibody assessment is described for the immunogenicity analysis set, but the record does not report its membership or how it relates to the enrollment figure.
Intervention
A single dose of Menactra®, a meningococcal groups A, C, Y and W-135 polysaccharide diphtheria toxoid conjugate vaccine. The study objectives concern antibody titers measured by the serum bactericidal assay using baby rabbit complement and the safety profile after vaccination.
Comparator
The record does not identify a separate placebo, untreated, or active-comparator group. It describes three age cohorts within a non-randomized, parallel study. Those age groups are not a like-for-like control comparison, so differences between them should not be read as randomized treatment effects.
Primary question
What antibody titers were measured before vaccination and 21 days after vaccination, including the number of participants with titers at or above 8, and what safety profile was recorded after a single dose? The registry record states these objectives but does not report the antibody-titer counts or an analysis comparing measurements over time.
3. Trial Design
This completed phase 3 study evaluated safety and immunogenicity of Menactra® in healthy subjects in India. The registry record lists Sanofi as sponsor, a planned enrollment of 300, and a start in June 2010 with primary completion in February 2011. It describes a parallel model, non-randomized allocation, and no masking.
Participants were assigned to age cohorts: children aged 2 to 11 years, adolescents aged 12 to 17 years, and adults aged 18 to 55 years. The record describes vaccination with a single dose. It does not describe a separate control intervention or a randomized allocation process. The cohorts therefore provide age-group descriptions, not randomized treatment and control arms.
The primary objectives were to describe SBA-BR antibody titers before and after vaccination and to describe the safety profile after vaccination. The primary antibody endpoint is framed as a count of participants with titers at or above 8 at baseline and 21 days post-vaccination. The registry lists four outcome measures but no analyses. The exact methods used to summarize outcomes, the composition of the analysis sets, and any comparisons between time points are not reported in the registry record.
Because allocation was non-randomized and no masking was used, the design is primarily descriptive as recorded. The presence of age cohorts does not itself create a concurrent control group. The registry record does not report a protocol rationale for the design, a sample-size justification, or a statistical analysis plan. Those omissions limit what can be concluded about the intended inferential role of the endpoint.
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 the inclusion and exclusion criteria were enrolled and vaccinated.
Overall Study
| Stage | Age 2 to 11 Years Group | Age 12 to 17 Years Group | Age 18 to 55 Years Group |
|---|---|---|---|
| STARTED | 100 | 100 | 100 |
| COMPLETED | 99 | 98 | 100 |
| NOT COMPLETED | 1 | 2 | 0 |
Reasons for not completing this period:
| Reason | Age 2 to 11 Years Group | Age 12 to 17 Years Group | Age 18 to 55 Years Group |
|---|---|---|---|
| Withdrawal by Subject | 1 | 2 | 0 |
Analysis population for the primary outcome, as defined in the registry: Menactra vaccine antibody titers were determined in the immunogenicity 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 | Age 2 to 11 Years Group | Age 12 to 17 Years Group | Age 18 to 55 Years Group | Total |
|---|---|---|---|---|---|
| Participants analysed | 100 | 100 | 100 | 300 | |
| Age, Categorical: <=18 years | Participants | 100 | 100 | 0 | 200 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 | 0 | 100 | 100 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 | 0 |
| Age Continuous | Years | 7.2 (SD 3.1) | 14.2 (SD 1.4) | 34.8 (SD 9.2) | 18.7 (SD 13.1) |
| Sex: Female, Male: Female | Participants | 53 | 48 | 38 | 139 |
| Sex: Female, Male: Male | Participants | 47 | 52 | 62 | 161 |
| Region of Enrollment: India | Participants | 100 | 100 | 100 | 300 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants With Vaccine Antibody Titers at ≥ 8 Before and After Menactra Vaccination, measured over Baseline and 21 days post-vaccination.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint counts participants whose Menactra vaccine antibody titer meets the stated threshold of 8. Titers were measured using the serum bactericidal assay with baby rabbit complement, abbreviated SBA-BR. The scheduled assessment points were baseline and 21 days post-vaccination. The registry record says the antibody titers were determined in the immunogenicity analysis set.
A threshold-based count turns a laboratory measurement into a binary outcome for each participant: the titer either reaches the stated threshold or it does not. Reporting the count at each assessment can describe how many participants met that criterion at each time point. It does not, by itself, show the distribution of individual titers, the size of any within-participant change, or whether the same participants contributed measurements at both assessments.
Serum bactericidal activity is used as an immunogenicity measure because it assesses antibody-related bactericidal activity in the assay described by the registry. The endpoint therefore addresses an immune-response measure, not a direct count of clinical meningococcal infections. The registry record does not provide the actual counts at either assessment, the underlying individual titers, or a statistical comparison of baseline with follow-up. The criterion and assessment schedule are reported, but the numerical antibody results are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a descriptive antibody objective: report titers before vaccination and after vaccination, and count participants meeting the threshold of 8. It also identifies a safety objective. However, it does not report the primary endpoint counts at baseline or 21 days post-vaccination. Without those values, the direction and size of any change in the threshold-based count cannot be described from the registry record. There is also no reported estimate of the change, uncertainty interval, or hypothesis-test result.
The design matters for interpretation. Allocation was non-randomized, masking was absent, and the record describes age cohorts rather than a separate control group. Consequently, the age groups should not be treated as randomized comparators, and the record does not support attributing differences between them to treatment. The study objectives focus on a single dose and before-and-after antibody measurement; the record does not report a formal paired analysis or other inferential method.
The posted safety figures list zero serious adverse events among the 100 participants at risk in each age group. For other adverse events, the record lists 30 in the age 2 to 11 years group, 23 in the age 12 to 17 years group, and 38 in the age 18 to 55 years group, with 100 participants at risk in each group. These are counts as recorded; the record does not provide event descriptions, severity details for the other events, timing, or an attribution assessment. Death figures are not reported in the registry record.
Counts alone do not establish that an event was caused by vaccination, and a zero recorded serious-event count does not establish that serious events cannot occur. The registry record does not report confidence intervals or other measures of uncertainty for these safety counts. It also does not explain whether all enrolled participants contributed to each outcome or whether missing observations affected the reported figures.
Overall, the record describes the study question and selected safety counts, but not the antibody outcome values or statistical analyses. Conclusions about the magnitude or precision of immunogenicity findings cannot be drawn from the information reported. The age-group safety counts are descriptive and should not be read as a causal comparison between cohorts.
9. Statistical Methods Explained
What does a threshold-based antibody count represent?
General statistical explanation: A binary endpoint classifies each observed measurement according to whether it meets a prespecified criterion. The resulting count is easy to interpret as a tally of participants meeting that criterion, but it discards information about how far measurements lie above or below the threshold. Two groups can have the same count while having different distributions of underlying measurements. Conversely, different counts do not reveal the magnitude of individual changes.
In this study, the registry identifies a threshold of 8 and assessments at baseline and 21 days post-vaccination. It says titers were measured with SBA-BR and describes the immunogenicity analysis set. The actual counts and individual measurements are not reported in the registry record. It is therefore not possible to reconstruct a change estimate or assess the distribution of antibody titers from the recorded information.
How should repeated measurements be understood?
General statistical explanation: When the same participant is measured at multiple times, the observations are related. A method that accounts for that pairing can distinguish within-participant change from differences between unrelated groups. A simple comparison of separate time-point totals may not preserve that information, especially if the participants contributing data differ between time points.
The registry gives baseline and follow-up assessment times but does not report whether the same participants were included at each assessment, how incomplete pairs were handled, or what method was used to compare the measurements. No particular paired or unpaired analysis should be inferred from the endpoint description alone.
What do uncertainty intervals and tests add?
General statistical explanation: A confidence interval describes a range of values compatible with an estimate under the assumptions of the chosen method. Its width communicates precision: wider intervals indicate less precision, while narrower intervals indicate more precision. A hypothesis test addresses compatibility with a specified null hypothesis, but a p-value does not measure the size or clinical importance of an effect.
The registry record does not report an antibody estimate, confidence interval, or p-value for the primary endpoint. It lists four outcome measures and zero analyses. The record therefore does not establish whether inferential tests were conducted, which hypotheses they would address, or how estimates were calculated. The absence of a reported analysis is not evidence that an analysis found no effect; it means those results are not reported in the registry record.
What can be inferred from counts in age groups?
General statistical explanation: Counts describe the observations recorded in a group. Comparing counts between groups requires attention to denominators, group formation, baseline differences, and the study design. Random allocation can support a causal comparison by balancing measured and unmeasured characteristics on average, while non-randomized groups may differ for reasons unrelated to the intervention.
Here, the record identifies non-randomized allocation and three age cohorts. It does not describe a separate control group, nor does it report adjustment for differences among cohorts. The age groups can be described separately, but a difference between them would not, on its own, estimate a treatment effect. The safety counts should likewise be read as descriptive group totals rather than evidence of a causal age-group contrast.
What is over-dispersion, and is it relevant?
General statistical explanation: Over-dispersion occurs when the variability in count data is greater than a statistical model assumes. If a model ignores that extra variability, uncertainty can be understated. Whether over-dispersion is relevant depends on the outcome structure and the model used; it should not be assumed merely because an outcome is reported as a count.
The record gives participant counts for a threshold-based antibody outcome and adverse-event tallies, but does not identify a count model or any model-based analysis. It does not report evidence about over-dispersion, so no conclusion on that issue can be drawn for this study.
How should planning calculations be distinguished from trial results?
General statistical explanation: A sample-size calculation is a planning exercise based on assumptions about an effect, variability, allocation, and error rates. It is not a measure of the probability that a completed study detected an effect. Such calculations should not be described as observed power.
The registry record characterizes its sample-size assumptions as a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It states that the effect to detect is a fraction of the observed effect and that non-time-to-event outputs are expressed as participants per arm. These assumptions do not describe the recorded non-randomized design of three age cohorts in an obvious like-for-like way. The record does not provide the effect estimate or the numerical planning outputs needed to evaluate the illustration. The planning assumptions should not be mistaken for the study's design justification or for evidence about the trial's achieved power.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists four outcome measures and identifies primary objectives related to antibody titers and safety. It lists zero analyses. It does not report a multiplicity strategy, such as a hierarchy of tests, an adjustment to control the chance of false-positive findings across multiple tests, or a statement that the outcomes are descriptive without formal testing. Because no analysis results are reported, the implications of multiple outcome measures for inferential claims cannot be assessed.
The antibody endpoint is described for the immunogenicity analysis set. The membership and definition of that set are not reported in the registry record. The record does not explain whether participants were excluded from that set, what criteria were used, or whether all enrolled participants were included in safety summaries.
Missing-data rules are not reported in the registry record. There is no description of how absent baseline or follow-up titers were handled, whether missingness was summarized, or whether any sensitivity analysis was planned or conducted. The record also does not state whether the displayed adverse-event counts reflect complete follow-up for every participant at risk.
A statistical analysis plan, including prespecified handling of multiplicity and missing data, is not reported in the registry record. These gaps mean the available record cannot establish how the analyses were selected, whether all prespecified analyses are represented, or how incomplete outcome data could affect interpretation.
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 |
|---|---|---|---|
| Age 2 to 11 Years Group | 0 | 100 | 0.0% |
| Age 12 to 17 Years Group | 0 | 100 | 0.0% |
| Age 18 to 55 Years 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 |
|---|---|
| Age 2 to 11 Years Group | 30 of 100 |
| Age 12 to 17 Years Group | 23 of 100 |
| Age 18 to 55 Years Group | 38 of 100 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Age 2 to 11 Years Group | Age 12 to 17 Years Group | Age 18 to 55 Years Group |
|---|---|---|---|---|
| Injection site pain | General disorders | 30 of 100 | 23 of 100 | 38 of 100 |
| Headache | Nervous system disorders | 12 of 100 | 19 of 100 | 19 of 100 |
| Myalgia | Musculoskeletal and connective tissue disorders | 13 of 100 | 8 of 100 | 12 of 100 |
| Malaise | General disorders | 9 of 100 | 13 of 100 | 5 of 100 |
| Fever | General disorders | 11 of 100 | 3 of 100 | 5 of 100 |
| Injection site swelling | General disorders | 10 of 100 | 4 of 100 | 0 of 100 |
| Injection site erythema | General disorders | 7 of 100 | 1 of 100 | 0 of 100 |
The registry record lists zero serious adverse events among the 100 participants at risk in each of the three age groups: ages 2 to 11 years, ages 12 to 17 years, and ages 18 to 55 years. It separately lists other adverse-event counts of 30, 23, and 38 for those groups, respectively, with 100 participants at risk in each group. These figures are descriptive counts as entered in the registry.
A zero recorded serious-event count means that no serious events are listed for the stated group in this record; it does not demonstrate that the underlying risk is zero. The registry does not report confidence intervals, event follow-up duration, event-level descriptions, or the method used to assess whether an event was related to vaccination. Death counts are not reported in the registry record.
The other-event counts should not be interpreted as comparisons of risk between ages without additional context. The study is non-randomized, and the record does not report details about event types, severity, or completeness of reporting. Counts do not establish causation.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a completed phase 3 study in healthy subjects in India was designed to describe SBA-BR antibody titers before and after a single dose of Menactra® and to describe safety. It identifies the threshold used for the primary antibody count, the scheduled follow-up assessment, and the three age cohorts. It also reports selected adverse-event counts by age group.
The record does not report the antibody counts at baseline or follow-up, individual titer values, or a statistical comparison over time. It therefore does not show the size or precision of any antibody change in the recorded results. Without those values, no conclusion about the frequency of participants meeting the antibody threshold can be made from the registry record.
The safety entries describe zero serious adverse events in each group and counts for other adverse events. These entries do not establish that vaccination caused or prevented any event. They also do not establish absence of risk, and the registry does not provide enough detail to interpret event severity, timing, or attribution. The age cohorts are not randomized controls, so comparisons between them would not isolate treatment effects.
These limitations concern what can be concluded from the registry record, not necessarily what may have been measured or analyzed outside it. The record does not report a full statistical plan, analysis-set definitions, missing-data procedures, uncertainty intervals, or the rationale for the sample-size planning illustration. The study's stated objectives and reported counts can be described, but stronger claims about efficacy, comparative effects, or precision are not supported by the information reported.
13. Why This Trial Matters Statistically
This trial illustrates the distinction between a clearly stated endpoint and a fully reported statistical result. The registry specifies an assay, a threshold, assessment times, and an analysis population description. Those details define what the investigators intended to measure. But without the corresponding antibody counts or estimates, readers cannot assess the observed immunogenicity pattern or its precision.
It also highlights why study design determines what comparisons mean. The registry describes non-randomized age cohorts and no separate control group. Cohort-specific descriptions can be useful, but age groups are not substitutes for randomized treatment and control arms. A statistical contrast between cohorts would not automatically represent a treatment effect.
Safety reporting presents a related lesson. A count of zero serious adverse events is informative as a record of observed events, but it is not equivalent to proof that the risk is absent. Interpretation depends on follow-up, event definitions, completeness, and uncertainty, several of which are not reported in the registry record. Other adverse-event counts likewise require context before comparisons are made.
Finally, planning calculations and analysis results answer different questions. A planning illustration depends on assumptions about effect size, allocation, and statistical methods; it does not report what the trial observed or establish achieved power. In this record, the stated two-arm planning assumptions sit alongside a non-randomized design with three age cohorts, so the assumptions need to be kept separate from the trial description. Taken together, these features show why statistical interpretation depends not only on outcome definitions, but also on transparent reporting of estimates, uncertainty, analysis populations, and design.
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 include the numerical results for the primary antibody endpoint. Although it defines the threshold and assessment times, the counts of participants meeting the threshold are not reported. No titer distributions, change estimates, confidence intervals, or hypothesis-test results are reported either.
The design is non-randomized, unmasked, and organized into age cohorts. The record does not identify a concurrent control group. These features limit causal interpretation and make age-group contrasts unsuitable as direct treatment comparisons. The registry does not report whether adjustment for baseline differences was performed.
Important details of the outcome analysis are absent. The immunogenicity analysis set is named, but its definition and membership are not reported. Missing-data procedures, completeness of follow-up, analysis methods, and a statistical analysis plan are not reported in the registry record. The number of analyses listed is zero, so it is not possible to identify inferential methods or evaluate how results were selected.
Safety information is also limited. The record reports group counts for serious and other adverse events, but does not provide event descriptions, timing, severity details for other events, attribution, or uncertainty estimates. Death counts are not reported in the registry record. The record does not provide the rationale for the sample-size planning illustration or the numerical outputs needed to evaluate its assumptions.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Study of Meningococcal Vaccine, Menactra® in Healthy Subjects in India — NCT01086969.
- Registry record last updated 2012-02-06; status last verified 2012-02.
- Results first posted 2012-02-03.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
This completed phase 3 study evaluated the safety and immunogenicity of a single dose of Menactra® in healthy subjects in India. The registry lists Sanofi as sponsor, enrollment of 300, and a study start in June 2010 with primary completion in February 2011.
The design is recorded as parallel, non-randomized, and unmasked. Participants were described in age cohorts of 2 to 11 years, 12 to 17 years, and 18 to 55 years. The primary antibody outcome concerns the number of participants with SBA-BR titers at or above 8 at baseline and 21 days post-vaccination.
The registry lists four outcome measures and zero analyses. It reports zero serious adverse events among the 100 participants at risk in each age group and other adverse-event counts of 30, 23, and 38 by age group. The primary antibody counts, statistical analyses, and several analysis and missing-data details are not reported in the registry record.