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 of a Meningococcal (Groups A, C, Y and W-135) Polysaccharide Diphtheria Toxoid Conjugate Vaccine in Healthy Subjects in Vietnam (NCT02640404), a non-randomized phase 2 study. The primary outcome is Number of Participants Reporting Solicited Injection-Site Reactions Following Vaccination: Menactra® Vaccine (9 to 23 Months).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02640404 |
| Phase | Phase 2 |
| Condition | Meningitis, Meningococcal Meningitis, Meningococcal Infections |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 224 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sanofi Pasteur, a Sanofi Company |
| Results posted | Yes |
2. Clinical Question
Population
Healthy participants aged 9 months to 55 years in Vietnam. The primary outcome concerns the Menactra® Vaccine group aged 9 to 23 months; a separate group covers ages 2 to 55 years. The safety analysis set included participants who received at least one dose.
Intervention
Menactra®, a meningococcal groups A, C, Y and W-135 polysaccharide diphtheria toxoid conjugate vaccine. Participants aged 9 to 23 months received a two-dose series, with the first dose on Day 0 and the second dose 3 months after the first. Participants aged 2 to 55 years received one dose on Day 0.
Comparator
The registry lists two age-based vaccine groups, not a randomized control group. The groups differ in age range and dosing schedule, and the record explicitly cautions that they are not a like-for-like control comparison.
Primary question
Among participants aged 9 to 23 months, how many reported solicited injection-site reactions after vaccination? The endpoint includes any Grade 1, 2 or 3 reaction and Grade 3 reactions, assessed within 7 days after each applicable vaccination.
The study objective was to describe the vaccine’s safety profile after each and any dose, when applicable, in participants aged 9 months to 55 years. The trial record describes safety monitoring rather than a comparison of vaccine efficacy. It lists 4 outcome measures, but the primary outcome information contains no participant counts for injection-site reactions. Consequently, the registry record does not establish the frequency of those reactions from the outcome information available for this analysis.
The registry identifies the study as phase 2 and non-randomized, with a parallel model and no masking. Its two arms cover substantially different age ranges and dosing schedules. Because assignment was not randomized and the groups are not described as equivalent controls, differences between group-level safety counts cannot be attributed to age, dose schedule, or vaccine exposure alone. The record’s central question is therefore descriptive: what safety events were recorded in the enrolled groups, and how completely are the outcomes reported?
3. Trial Design
The registry describes a completed phase 2, non-randomized, parallel study sponsored by Sanofi Pasteur, a Sanofi Company. It lists healthy subjects in Vietnam, with an intended age range of 9 months to 55 years. The listed enrollment is 224. The record gives a study start date of 2016-06-06 and a primary completion date of 2016-12-05.
Two vaccine groups are listed. Participants aged 9 to 23 months received a two-dose series, with the first dose at Day 0 and the second dose 3 months after dose 1. Participants aged 2 to 55 years received one dose at Day 0. Both groups are described as receiving the same named vaccine intervention. The record does not describe a placebo or an untreated control group.
The allocation is non-randomized and masking is listed as none. The parallel model means the record presents separate groups rather than describing a crossover sequence. These design features matter to interpretation: the groups are not randomized, their age ranges differ, and their dosing schedules differ. The registry itself cautions that they are not a like-for-like control comparison. Any contrast between their reported counts is therefore descriptive, not a randomized treatment-effect estimate.
The primary outcome is a count of participants reporting solicited injection-site reactions in the 9-to-23-month group. Its assessment windows are within 7 days after vaccination 1 and within 7 days after vaccination 2. The safety analysis set included participants who received at least one study-vaccine dose. Although the record lists 4 outcome measures, it lists 0 analyses. The statistical plan, including any prespecified comparison procedures or methods for handling repeated assessments, is not reported in the registry record. The study is marked completed, but completion status alone does not supply the missing outcome estimates.
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 224 participants (112 for each group) were enrolled and vaccinated in the study.
Overall Study
| Stage | Menactra® Vaccine (9 to 23 Months) | Menactra® Vaccine (2 to 55 Years) |
|---|---|---|
| STARTED | 112 | 112 |
| COMPLETED | 110 | 112 |
| NOT COMPLETED | 2 | 0 |
Reasons for not completing this period:
| Reason | Menactra® Vaccine (9 to 23 Months) | Menactra® Vaccine (2 to 55 Years) |
|---|---|---|
| Protocol Violation | 1 | 0 |
| Withdrawal by Subject | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: Safety analysis set included all participants who received at least 1 dose of study vaccine.
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: Safety analysis set included all participants who received at least 1 dose of study vaccine.
| Characteristic | Unit | Menactra® Vaccine (9 to 23 Months) | Menactra® Vaccine (2 to 55 Years) | Total |
|---|---|---|---|---|
| Participants analysed | 112 | 112 | 224 | |
| Age, Customized: 9 to 23 months | Participants | 112 | 0 | 112 |
| Age, Customized: 2 to 11 years | Participants | 0 | 43 | 43 |
| Age, Customized: 12 to 17 years | Participants | 0 | 33 | 33 |
| Age, Customized: 18 to 55 years | Participants | 0 | 36 | 36 |
| Sex: Female, Male: Female | Participants | 52 | 57 | 109 |
| Sex: Female, Male: Male | Participants | 60 | 55 | 115 |
| Region of Enrollment: Vietnam | participants | 112 | 112 | 224 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants Reporting Solicited Injection-Site Reactions Following Vaccination: Menactra® Vaccine (9 to 23 Months), measured over Within 7 days post-vaccination 1, Within 7 days post-vaccination 2.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary outcome is the number of participants aged 9 to 23 months who reported solicited injection-site reactions after vaccination. The registry describes tenderness or pain, erythema, and swelling. It gives severity grades for these reactions, with Grade 1, Grade 2, and Grade 3 definitions. The endpoint reports participants with any Grade 1, 2 or 3 solicited injection-site reaction, as well as participants with Grade 3 reactions.
The assessment timeframe is within 7 days after vaccination 1 and within 7 days after vaccination 2. These short, specified windows make the endpoint a structured account of reactions actively solicited after dosing, rather than an unrestricted count of any health event over an unspecified period. The registry describes the outcome as a participant count, so the intended unit is people reporting a reaction, not the total number of reaction episodes.
In general, solicited safety outcomes can help characterize common, predefined reactions in a consistent way, while severity grading distinguishes reactions by the recorded criteria. That general purpose does not establish how complete reporting was or whether the outcome was measured identically across participants; further details are not reported in the registry record. The registry record supplies the endpoint definition and timeframe but no observed counts, estimates, or uncertainty intervals for this primary outcome. Its frequency and precision therefore cannot be assessed from the outcome information recorded.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies a safety question and describes how the primary injection-site outcome was defined, but the outcome record does not give the number of participants reporting reactions. Without those counts, there is no reported primary-outcome estimate to interpret. The record also lists 0 analyses. It therefore does not provide a statistical test, confidence interval, or adjusted estimate for this endpoint. The study’s completed status does not fill that reporting gap.
The two group descriptions should not be read as a controlled comparison. The 9-to-23-month group followed a two-dose schedule, while the 2-to-55-year group received one dose. The age ranges differ, allocation was non-randomized, and the registry explicitly warns that the arms are not a like-for-like control comparison. An apparent difference in recorded safety counts would not isolate a vaccine effect or explain why the groups differed. The available record does not report a comparative analysis that addresses those limitations.
The serious adverse event summary lists 16 affected participants among 112 at risk in the 9-to-23-month group and 0 among 112 at risk in the 2-to-55-year group. These are descriptive group-level figures, not randomized comparative estimates. The record also lists 86 participants with other adverse events in the younger group and 49 in the older group, each among 112 at risk. These counts do not replace the missing primary injection-site outcome results, and the registry record does not provide an analysis that puts the categories into a common comparative framework.
The serious-event terms listed with percentages include bronchiolitis and pneumonia at 2.7% each; hand-foot-and-mouth disease, viral infection, and febrile convulsion at 1.8% each; and diarrhoea at 0.9%. The registry does not explain the term-level denominators or provide further context for interpreting these percentages. It lists 0 deaths in each group. These descriptions should be read as registry safety reporting, not as evidence that any listed event was caused by vaccination.
In general, an estimate is more informative when its uncertainty is reported alongside it. No confidence intervals or other uncertainty measures for these safety counts are listed in the registry record. The record also does not report a statistical analysis plan, adjustment for group differences, or inferential comparison. Thus the data support a limited descriptive reading of the adverse-event summaries, while the primary outcome remains unevaluable from the posted outcome information.
9. Statistical Methods Explained
The registry record identifies participant counts as the outcome type and lists no analyses. It does not report the inferential methods used for the primary endpoint, any model, or any hypothesis test. The methods discussion below is general statistical context, not a claim about procedures used in this study.
What does a participant count describe?
For a binary safety outcome, each participant is classified according to whether the event was reported during the defined observation window. A count describes how many participants in the relevant analysis group met that definition. A proportion would additionally relate that count to an eligible denominator, but no primary injection-site reaction counts or corresponding estimates are listed in the registry record. The serious and other adverse-event summaries do list counts and at-risk group sizes, but those summaries address different event categories from the primary solicited injection-site outcome.
Counts and proportions answer descriptive questions. They do not, by themselves, establish whether a difference between groups is attributable to treatment. Comparisons require attention to how groups were formed, whether the outcome definitions and follow-up are comparable, and how uncertainty is quantified. Here, allocation was non-randomized, and the age ranges and dosing schedules differ. The registry cautions against treating the groups as a like-for-like control comparison.
What would a confidence interval convey?
In general, a confidence interval describes the statistical uncertainty around an estimate under a specified method and its assumptions. A narrower interval indicates greater precision under that method; a wider interval indicates less precision. It is not a guarantee about the range of individual outcomes, and it does not resolve biases created by non-random allocation or incomplete reporting. The registry record does not report confidence intervals for the primary outcome or the adverse-event summaries.
What would a hypothesis test convey?
In general, a hypothesis test evaluates how compatible observed data are with a specified statistical model and null hypothesis. A p-value is not the probability that a treatment is effective, nor does it measure clinical importance. Its interpretation depends on the prespecified question, analysis method, and assumptions. No p-value or test for the primary outcome is reported in the registry record. Since the record lists no analyses, it is not possible to determine whether a test was planned or performed.
Why do design features matter?
Random allocation can help balance measured and unmeasured characteristics between groups on average, whereas non-random allocation can leave groups differing for reasons related to participant selection or other factors. This is general design reasoning, not a claim that a specific imbalance occurred in this study. In this record, the groups are explicitly age-based and receive different dose schedules. Those features make a direct between-group contrast especially difficult to interpret as an effect attributable to the vaccine.
Masking can reduce the influence of knowledge of treatment assignment on some aspects of outcome reporting or assessment. The registry lists masking as none. It does not report whether any additional safeguards were used in soliciting or classifying reactions. The endpoint’s defined reaction categories and grade criteria offer a structured outcome definition, but the record does not describe the operational procedures or assessment reliability.
How should the planning calculations be read?
The registry’s sample-size assumptions describe planning illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The assumed effect to detect is stated as a fraction of the observed effect. These are planning illustrations, not observed power and not proof that the study was designed with those assumptions. The record does not report the trial’s own sample-size justification, and the planning output values are not included in the registry entries for this analysis.
In general, an assumed target effect and allocation scheme can be used to illustrate how much information a future study might require under chosen statistical assumptions. Such an illustration depends on the assumptions and on the estimate used as its reference. It does not show the probability that this completed study detected an effect, and it cannot recover an unreported primary outcome estimate. The registry record does not report the origin or precision of the observed effect used for the planning illustration.
Because the record provides no primary reaction counts, no analysis results, and no uncertainty estimates, the most defensible statistical reading is descriptive and limited. The reported event summaries can be stated as recorded, but they cannot support a more detailed inferential conclusion.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 4 outcome measures and 0 analyses. It does not report whether the outcomes were arranged in a prespecified hierarchy, whether multiple comparisons were planned, or whether any adjustment for multiplicity was used. Multiplicity refers generally to the statistical challenge that arises when several outcomes or comparisons are examined: the chance of at least one apparently notable result can increase when many tests are conducted. This general concern cannot be quantified for this study from the registry record.
The primary endpoint covers any Grade 1, 2 or 3 solicited injection-site reaction and separately identifies Grade 3 reactions, with assessments after each applicable vaccination. The record does not report how the repeated post-vaccination observations were combined or analyzed, nor whether the outcome descriptions were linked to a prespecified testing strategy. No analysis details are reported in the registry record.
For missing data, the safety analysis set is described as all participants who received at least one dose. The record does not state how participants with incomplete follow-up, missing reaction assessments, or missing adverse-event information were handled. It does not report the number of participants with missing outcome data or any imputation method. Those details should not be inferred from group sizes in the adverse-event summary.
The registry also does not report a statistical analysis plan or explain whether any interim analyses took place. The absence of such information in the registry record does not establish that a procedure was or was not used; it means the procedure cannot be assessed from the record. The primary reaction counts and their uncertainty are likewise not reported, preventing an assessment of outcome completeness or precision.
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® Vaccine (9 to 23 Months) | 16 | 112 | 14.3% |
| Menactra® Vaccine (2 to 55 Years) | 0 | 112 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Menactra® Vaccine (9 to 23 Months) | 0 of 112 |
| Menactra® Vaccine (2 to 55 Years) | 0 of 112 |
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 |
|---|---|
| Menactra® Vaccine (9 to 23 Months) | 86 of 112 |
| Menactra® Vaccine (2 to 55 Years) | 49 of 112 |
Most frequent serious adverse event terms
| Event term | Organ system | Menactra® Vaccine (9 to 23 Months) | Menactra® Vaccine (2 to 55 Years) |
|---|---|---|---|
| Bronchiolitis | Infections and infestations | 3 of 112 | 0 of 112 |
| Pneumonia | Infections and infestations | 3 of 112 | 0 of 112 |
| Hand-foot-and-mouth disease | Infections and infestations | 2 of 112 | 0 of 112 |
| Viral infection | Infections and infestations | 2 of 112 | 0 of 112 |
| Febrile convulsion | Nervous system disorders | 2 of 112 | 0 of 112 |
| Diarrhoea | Gastrointestinal disorders | 1 of 112 | 0 of 112 |
| Diarrhoea infectious | Infections and infestations | 1 of 112 | 0 of 112 |
| Gastrointestinal infection | Infections and infestations | 1 of 112 | 0 of 112 |
| Respiratory tract infection | Infections and infestations | 1 of 112 | 0 of 112 |
| Tonsillitis | Infections and infestations | 1 of 112 | 0 of 112 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Menactra® Vaccine (9 to 23 Months) | Menactra® Vaccine (2 to 55 Years) |
|---|---|---|---|
| Injection site pain | General disorders | 23 of 112 | 28 of 112 |
| Decreased appetite | Metabolism and nutrition disorders | 32 of 112 | 0 of 112 |
| Pyrexia | General disorders | 24 of 112 | 7 of 112 |
| Malaise | General disorders | 0 of 112 | 24 of 112 |
| Nasopharyngitis | Infections and infestations | 24 of 112 | 0 of 112 |
| Myalgia | Musculoskeletal and connective tissue disorders | 0 of 112 | 20 of 112 |
| Vomiting | Gastrointestinal disorders | 18 of 112 | 1 of 112 |
| Headache | Nervous system disorders | 0 of 112 | 17 of 112 |
| Irritability | Psychiatric disorders | 16 of 112 | 0 of 112 |
| Crying | General disorders | 15 of 112 | 0 of 112 |
Serious events with the highest arm-level rate: bronchiolitis (2.7%), pneumonia (2.7%), hand-foot-and-mouth disease (1.8%), viral infection (1.8%), febrile convulsion (1.8%).
The serious adverse-event summary lists 16 affected participants among 112 at risk in the Menactra® Vaccine group aged 9 to 23 months, and 0 affected participants among 112 at risk in the group aged 2 to 55 years. The record lists 0 deaths in each group. These are descriptive counts as recorded; they are not adjusted estimates and do not establish a causal relationship between vaccination and an event.
The listed serious-event terms and percentages are bronchiolitis, 2.7%; pneumonia, 2.7%; hand-foot-and-mouth disease, 1.8%; viral infection, 1.8%; febrile convulsion, 1.8%; and diarrhoea, 0.9%. The registry record does not report term-level denominators, additional context for the percentages, or a comparative analysis of these terms. The terms therefore should not be interpreted as a ranked comparison between groups.
The record separately lists 86 participants with other adverse events among 112 at risk in the younger group and 49 among 112 at risk in the older group. It does not provide further detail in the registry record about how the other-event category relates to the serious-event category. The age ranges and dose schedules differ, allocation was non-randomized, and the registry cautions that the groups are not a like-for-like control comparison. Group-level counts should therefore be read as safety reporting, not as evidence of relative risk or vaccine causation.
12. What the Result Does, and Does Not, Mean
The record establishes that a phase 2 safety study of Menactra® was conducted in healthy participants in Vietnam, with age-based groups and different dosing schedules. It specifies a primary solicited injection-site outcome in the 9-to-23-month group, including reaction severity categories and short post-vaccination assessment windows. It also gives descriptive serious and other adverse-event counts, listed serious-event terms, and death counts.
It does not report the primary injection-site reaction counts. That omission means the frequency of the primary endpoint cannot be summarized from the registry outcome information. The record also lists 0 analyses and does not report confidence intervals, p-values, or a statistical plan. There is consequently no reported inferential estimate for the primary outcome and no basis in the registry record for judging its precision.
The serious adverse-event counts are not a randomized comparison. The groups differ in age range and dose schedule, and the registry explicitly warns that they are not a like-for-like control comparison. The numbers should not be used to conclude that one age group had greater or lesser risk because of vaccination. Nor do listed event terms establish that the vaccine caused those events. The record supplies no causal analysis.
In general, a safety study can describe observed events in its enrolled population, but the strength of any conclusion depends on complete outcome reporting, follow-up, design, and statistical uncertainty. The record identifies the safety analysis set as participants who received at least one dose, yet does not describe missing outcome handling. It also does not report the term-level denominators for the listed serious-event percentages.
The trial record therefore offers some descriptive safety information, but it does not provide enough primary-outcome or statistical detail to make a precise estimate of solicited injection-site reactions or to support causal comparisons between the groups. These limits concern the information reported in the registry record; they do not establish what unreported analyses or results may exist elsewhere.
13. Why This Trial Matters Statistically
This trial is statistically notable because it illustrates the difference between defining an outcome and reporting an estimate for that outcome. The registry describes solicited injection-site reactions in detail, including reaction types, grades, and assessment windows. Yet the primary outcome information does not include the participant counts needed to summarize how often the reactions were reported. A clear outcome definition is useful, but it cannot substitute for the observed results.
The design also highlights why group structure matters. The two groups are non-randomized and differ both in age range and dosing schedule. The registry warns that they are not a like-for-like control comparison. This prevents a simple interpretation of differences in adverse-event counts as evidence of a treatment effect. Statistical methods cannot, by themselves, make fundamentally different groups exchangeable or eliminate confounding when the relevant information is not reported.
The record further separates descriptive safety summaries from inferential analysis. Serious adverse-event counts and percentages can document what the registry lists, but no analyses, uncertainty intervals, or statistical plan are reported. Readers therefore cannot assess the precision of estimates or determine whether any comparisons were prespecified.
Finally, planning assumptions should not be confused with evidence from the completed study. The described calculations are illustrations based on an observed effect and stated assumptions, not observed power. The record does not report its own sample-size justification. This distinction matters when planning information is presented alongside a study whose primary outcome results are not available in the registry outcome record.
Taken together, the record is a useful example of how outcome definitions, design, event counts, and analysis reporting each contribute distinct pieces of statistical evidence. Missing elements constrain interpretation, even when the study is marked completed and the safety objective is clearly stated.
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 outcome is described but its observed participant counts are not reported in the registry record. This prevents direct assessment of the primary endpoint’s frequency and precision. Although the safety analysis set is defined as participants who received at least one vaccine dose, the record does not report the number with complete injection-site assessments or how missing assessments were handled.
The study was non-randomized and had no masking. The two groups cover different age ranges and follow different dosing schedules; the registry specifically cautions that they are not a like-for-like control comparison. These design features limit causal interpretation of between-group differences. The record does not describe adjustment for group differences or report a comparative model.
The registry lists 4 outcome measures and 0 analyses. It does not report a statistical analysis plan, hypothesis tests, confidence intervals, or an approach to multiplicity. The extent and timing of follow-up for adverse events beyond the primary endpoint’s stated windows are not reported in the registry record. The term-level denominators for the listed serious adverse-event percentages are also not reported.
The listed enrollment and the adverse-event group sizes do not supply the missing primary outcome results. No study-specific sample-size justification is reported; the described planning calculations are illustrations based on an observed effect and specified assumptions. The registry record does not provide the planning output values for this analysis. These reporting and design limits restrict the conclusions that can be drawn from the registry safety summaries.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Safety of a Meningococcal (Groups A, C, Y and W-135) Polysaccharide Diphtheria Toxoid Conjugate Vaccine in Healthy Subjects in Vietnam — NCT02640404.
- Registry record last updated 2018-01-08; status last verified 2017-12.
- Results first posted 2018-01-08.
- 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
The registry describes NCT02640404 as a completed phase 2, non-randomized, parallel safety study of Menactra® in healthy subjects in Vietnam aged 9 months to 55 years. The listed enrollment is 224. Participants aged 9 to 23 months received a two-dose series, while participants aged 2 to 55 years received one dose.
The primary outcome concerns solicited injection-site reactions in the 9-to-23-month group, assessed within 7 days after each applicable vaccination. The registry defines reaction types and grades but does not report the primary reaction counts. It lists 4 outcome measures and 0 analyses.
Safety summaries include serious and other adverse-event counts, serious-event terms with percentages, and 0 deaths in each group. The groups are not randomized and are not described as a like-for-like control comparison. The registry record does not report a statistical analysis plan, uncertainty estimates, or missing-data methods.