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 Immunogenicity and Safety of MenQuadfi® as a Booster Vaccine in Toddlers 12 to 23 Months, Regardless of the Quadrivalent Meningococcal Conjugate Vaccine Used for Priming in Infancy (NCT05929651), a na phase 4 study. The primary outcome is Percentage of Participants With Serum Bactericidal Assay Using Human Complement (hSBA) Antibody Titers >=1:8 Against Meningococcal Serogroups A, C, Y, and W.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05929651 |
| Phase | Phase 4 |
| Condition | Meningococcal Immunisation, Healthy Volunteers |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 71 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sanofi Pasteur, a Sanofi Company |
| Results posted | Yes |
2. Clinical Question
Population
Healthy toddlers 12 to 23 months of age in Argentina who had received at least 1 dose of Nimenrix® or Menveo® during infancy, before 12 months of age.
Intervention
A single booster dose of MenACYW conjugate vaccine, identified in the study title as MenQuadfi®. The dose was given at least 2 months after the last infant dose of Nimenrix® or Menveo®.
Comparator
There was no comparison group. This was an open-label, single-arm study, so the record does not provide a randomized or concurrent control comparison.
Primary question
What percentage of participants had hSBA antibody titers >=1:8 against meningococcal serogroups A, C, Y, and W before vaccination on Day 1 and 30 days after vaccination on Day 31, and what safety events were recorded?
The question is descriptive: it concerns antibody measurements in toddlers after a booster, rather than a comparison of the booster with another vaccine or with no booster. The registry identifies the primary measure as the percentage of participants meeting the stated hSBA threshold for each serogroup. It also describes safety follow-up after vaccination.
The registry enrollment is 71, but that number should not be assumed to be the denominator for every endpoint. The primary endpoint description says that the reported population was the per-protocol analysis set, a subset of the full analysis set, and that only participants with data for each specified serogroup were reported. The record does not report the endpoint percentages or the denominators underlying them. Consequently, the posted record does not answer the descriptive question with numerical antibody results.
3. Trial Design
This is a completed Phase IV, descriptive, open-label, single-arm, multi-center study. The registry lists enrollment of 71. Participants were healthy toddlers 12 to 23 months of age in Argentina who had received at least 1 dose of Nimenrix® or Menveo® during infancy, before 12 months of age. Each participant received a single booster dose of MenACYW conjugate vaccine, identified as MenQuadfi® in the study title. The booster was given at least 2 months after the last infant vaccination with Nimenrix® or Menveo®.
Because the study had one group and no masking, the design supports description of outcomes observed after vaccination but does not provide a direct comparison with another intervention. Allocation is listed as not applicable. The record does not report a control group, random assignment, or blinding. The study is described as descriptive, so its results should be read as observations in the enrolled study population rather than as a controlled estimate of a difference between treatments.
Immunogenicity was assessed using blood samples collected before vaccination on Day 1 and at the post-vaccination visit on Day 31, described as 30 days after vaccination on Day 1. The study also included a telephone call on Day 9 for safety follow-up. The record describes two visits and one safety telephone contact.
The registry lists a start date of 2023-09-07, a primary completion date of 2024-09-09, and a completed status. These dates describe the study record and do not supply additional endpoint results. The registry record does not report the rationale for the enrollment target, details of site-level conduct, or a statistical analysis plan explaining how the descriptive estimates were selected or interpreted.
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 71 participants were enrolled in this study.
Overall Study
| Stage | MenACYW Conjugate Vaccine |
|---|---|
| STARTED | 71 |
| Safety Analysis Set (SafAS) | 69 |
| COMPLETED | 68 |
| NOT COMPLETED | 3 |
Reasons for not completing this period:
| Reason | MenACYW Conjugate Vaccine |
|---|---|
| Protocol Deviation | 1 |
| Withdrawal by participant's parents/legally acceptable representatives | 2 |
Analysis population for the primary outcome, as defined in the registry: The per-protocol analysis set (PPAS) was a subset of the full analysis set (FAS). The FAS included participants who received the study vaccine and had a valid post-vaccination serology result. Only participants with data collected for each specified serogroup are reported.
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: Baseline characteristics were evaluated for study participants with data in case report form (CRF).
| Characteristic | Unit | MenACYW Conjugate Vaccine |
|---|---|---|
| Participants analysed | 71 | |
| Age, Continuous | months | 14.3 (SD 1.50) |
| Sex: Female, Male: Female | Participants | 34 |
| Sex: Female, Male: Male | Participants | 37 |
| Race and Ethnicity Not Collected | Participants | — |
6. Primary Endpoint
The registry lists the primary outcome as Percentage of Participants With Serum Bactericidal Assay Using Human Complement (hSBA) Antibody Titers >=1:8 Against Meningococcal Serogroups A, C, Y, and W, measured over Day 1 (pre-vaccination) and Day 31 (30 days post-vaccination on Day 1).
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | Percentage of participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the percentage of participants with hSBA antibody titers >=1:8 against meningococcal serogroups A, C, Y, and W. The measurement uses a serum bactericidal assay with human complement. The registry describes the assay as measuring functional meningococcal antibody activity. Results were intended at two times: Day 1 before vaccination and Day 31, 30 days after vaccination on Day 1.
Expressing the outcome as a percentage describes the share of the assessed participants who met the specified antibody threshold for each serogroup. A threshold-based endpoint can make a laboratory result easier to interpret as the proportion meeting a defined criterion, while retaining the important detail that the measure is an assay result. It is not, by itself, a direct count of clinical disease events.
The endpoint is reported with a 95% confidence interval. In general, a confidence interval conveys uncertainty around an estimated percentage; it does not guarantee that the true value lies within a particular interval. Its width depends on the amount and variability of the available data. The registry record does not report the endpoint percentages or the confidence interval limits, so the precision of the primary estimates cannot be assessed from the posted record.
The primary endpoint population is described as the per-protocol analysis set, a subset of the full analysis set. The full analysis set includes participants who received the study vaccine and had a valid post-vaccination serology result. Only participants with data for each specified serogroup are reported. These population rules matter because the denominator may differ by endpoint or serogroup; the record does not give the endpoint-specific denominators.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The design addresses a focused descriptive question: antibody measurements before and after a MenQuadfi® booster in toddlers primed in infancy with Nimenrix® or Menveo®. The registry states the assay, threshold, serogroups, and assessment times. However, it does not report the numerical primary endpoint results. Without the percentages, confidence interval limits, and endpoint denominators, readers cannot judge the observed antibody levels or the precision of those estimates from the posted record.
The before-and-after measurements are observations in the same single-group study context, not a randomized contrast. A change across time, if reported, would not by itself separate the booster’s contribution from other explanations such as measurement variation or changes over time. The registry record does not report a causal analysis or a comparator group. It therefore does not support a comparative treatment effect estimate.
The primary endpoint description refers to hSBA antibody activity and a threshold of >=1:8. The assay result is a laboratory measure of functional antibody activity, as described in the record. It should be interpreted as that measure, not as a direct observation of prevention of invasive meningococcal disease. The registry summary names protection against invasive meningococcal disease as the context for the study, but does not report disease outcomes as the primary measure.
The safety record lists 1 serious adverse event among 69 participants at risk in the MenACYW conjugate vaccine group, and 45 participants with other adverse events among 69 at risk. It lists 0 deaths. Febrile convulsion is the top serious term, reported as 1.4%. These entries describe events recorded in the study. They do not establish that the vaccine caused an event, and the record does not provide a comparison group from which to estimate a relative safety difference.
The registry lists enrollment of 71, while the safety denominators are 69. The primary endpoint description also defines an analysis population that may differ from enrollment. Those figures refer to different reporting contexts and should not be combined or treated as interchangeable. The record does not explain why the safety denominator differs from enrollment or provide a participant flow accounting for all enrolled participants.
Overall, the registry record gives useful design and endpoint definitions but limited numerical evidence for interpretation. The primary antibody percentages and their confidence intervals are not reported in the registry record. No analysis entries are listed. Thus, the posted information does not permit an assessment of the magnitude or precision of the primary immunogenicity estimates, nor a controlled comparison of outcomes.
9. Statistical Methods Explained
Statistical interpretation begins with the question the design can answer. This study has one group, with measurements before and after a booster. A single-group descriptive design can report the observed distribution of outcomes in that group. It cannot, without a comparison group and an appropriate comparative analysis, estimate how outcomes would differ under another intervention or without the booster. This distinction is important even when measurements are made at more than one time.
What does a percentage estimate?
A percentage is a way to describe the proportion of assessed participants who meet a specified outcome definition. Here, the definition is an hSBA antibody titer at or above the stated threshold for each serogroup. The percentage depends on the numerator—the participants meeting the criterion—and the denominator—the participants with data included under the analysis rules. If either is not reported, the estimate cannot be checked or fully interpreted. The primary endpoint description says that only participants with data for each specified serogroup are reported, but the posted record does not give the endpoint-specific counts or percentages.
Percentages for different serogroups are separate summaries. They should not be combined into a single overall percentage unless an analysis defines and reports such a summary. The registry specifies serogroups A, C, Y, and W, but does not provide the primary outcome values. It is therefore not possible to describe a pattern across serogroups or compare the precision of their estimates.
How should the confidence interval be read?
A confidence interval describes uncertainty around an estimate under the statistical method used to construct it. A narrower interval generally indicates greater precision than a wider interval, although interval width also depends on the method and the data. A confidence interval is not a range containing every participant’s result, and it does not express the probability that a particular fixed value is the true value. The registry specifies a 95% confidence interval for the primary measure, but does not report its limits. The actual precision therefore cannot be evaluated.
The interval and the point estimate answer related but different questions. The point estimate describes the observed percentage in the analysis population; the interval communicates uncertainty around that estimate. Neither, without a comparator or other supporting evidence, establishes a causal effect. Also, a confidence interval does not remedy missing endpoint information: if the estimate and its limits are not reported, readers cannot reconstruct the result without the underlying participant-level data and analysis method.
Why do analysis populations matter?
The registry describes a full analysis set that includes participants who received the study vaccine and had a valid post-vaccination serology result. It describes the per-protocol analysis set as a subset of the full analysis set, and identifies the per-protocol set for the primary endpoint. These definitions affect who contributes to an estimate. A per-protocol analysis can exclude participants who do not meet protocol-related criteria, while a broader analysis set may include more participants under its own eligibility rules. The record does not provide the complete criteria for the per-protocol set or the endpoint-specific denominators.
When the denominator varies by serogroup or time point, percentages can represent different subsets. In general, that can complicate comparisons across outcomes because the estimates may not describe exactly the same participants. The registry says that only participants with data for each specified serogroup are reported, but does not give the data completeness by serogroup or explain missing measurements. No missing-data method is reported in the registry record.
What can the design say about change over time?
Day 1 is the pre-vaccination assessment and Day 31 is the post-vaccination assessment, 30 days after vaccination on Day 1. Paired observations can describe how measurements in participants differ across these assessment times when both measurements are available. A descriptive before-and-after contrast still lacks the counterfactual comparison needed to attribute a change to the booster alone. The record does not report a paired analysis, a test of change, or numerical results for either time point.
Open-label status means the study is described as unmasked. For an objective laboratory assay, this does not automatically determine the direction or size of any bias. The registry does not report details about laboratory blinding, assay handling, or procedures for reducing measurement bias, so these aspects cannot be assessed from the record.
How should planning illustrations be interpreted?
General sample-size planning estimates depend on assumptions about the effect to detect, variability, significance level, allocation, and statistical method. The registry’s planning description refers to a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of an observed effect. For non-time-to-event outcomes, those illustrations are defined as participants per arm. They are planning illustrations, not observed power.
Those assumptions do not describe the actual study design, which is single-arm and has no like-for-like control comparison. The registry record does not report the numerical planning outputs or the observed effect used for the illustrations. They cannot be treated as the study’s design justification or as evidence that the trial had a particular probability of detecting an effect. The sample-size rationale and any prespecified power calculation are not reported in the registry record.
The registry lists no analysis entries. That means the record does not supply a detailed inferential analysis to interpret. It does not establish that no analyses were performed outside the registry; it means those analyses are not reported in the registry record. P-values, adjusted estimates, and a full statistical analysis plan are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The primary endpoint covers four meningococcal serogroups and two assessment times. When several outcomes or time points are considered, multiplicity can arise: the more statistical comparisons made, the greater the chance that at least one result appears notable by chance if each is judged separately. An analysis plan may address this through a prespecified primary comparison, an adjustment, or a descriptive approach. The registry describes the endpoint and time points but does not report a multiplicity strategy or a statistical analysis plan. The record also does not report inferential results or analysis entries, so it is not possible to determine whether any multiplicity adjustment was used.
The outcome is described as a percentage with a 95% confidence interval. The registry does not report the percentages, interval limits, or endpoint-specific denominators. It also does not report counts of participants with missing or invalid measurements at each assessment, reasons for missingness, or a method for handling missing observations. These omissions limit assessment of both the estimates and their potential sensitivity to incomplete data.
The full analysis set requires receipt of the study vaccine and a valid post-vaccination serology result. The primary outcome is described for the per-protocol analysis set, a subset of the full analysis set, and only participants with data for each specified serogroup are reported. These rules define who contributes, but the complete per-protocol criteria and participant flow are not reported in the registry record. The registry enrollment of 71 should therefore not be assumed to be the denominator for each primary outcome.
The record does not report an interim analysis plan, missing-data sensitivity analyses, or a detailed description of how confidence intervals were calculated. Those details are not reported in the registry record and should not be inferred from the study’s descriptive label alone.
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 |
|---|---|---|---|
| MenACYW Conjugate Vaccine | 1 | 69 | 1.4% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| MenACYW Conjugate Vaccine | 0 of 69 |
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 |
|---|---|
| MenACYW Conjugate Vaccine | 45 of 69 |
Most frequent serious adverse event terms
| Event term | Organ system | MenACYW Conjugate Vaccine |
|---|---|---|
| Febrile Convulsion | Nervous system disorders | 1 of 69 |
Most frequent non-serious adverse event terms
| Event term | Organ system | MenACYW Conjugate Vaccine |
|---|---|---|
| Irritability | Psychiatric disorders | 22 of 69 |
| Injection Site Pain | General disorders | 21 of 69 |
| Decreased Appetite | Metabolism and nutrition disorders | 14 of 69 |
| Crying | General disorders | 14 of 69 |
| Pyrexia | General disorders | 14 of 69 |
| Somnolence | Nervous system disorders | 13 of 69 |
| Vomiting | Gastrointestinal disorders | 13 of 69 |
| Diarrhoea | Gastrointestinal disorders | 5 of 69 |
| Nasopharyngitis | Infections and infestations | 4 of 69 |
| Injection Site Erythema | General disorders | 4 of 69 |
Serious events with the highest arm-level rate: febrile convulsion (1.4%).
The registry lists safety figures for the MenACYW conjugate vaccine group. It reports 1 serious adverse event among 69 participants at risk, 45 participants with other adverse events among 69 at risk, and 0 deaths. Febrile convulsion is identified as the top serious term, at 1.4%. These are the reported safety figures; they are not a comparison with another vaccine or an untreated group.
An adverse event is an event recorded during a study, and its occurrence does not by itself establish that the study intervention caused it. The registry’s safety summary does not provide a causal assessment for the listed event. The serious-event count and the top serious term should also be read as different descriptions: the former gives a count among participants at risk, while the latter gives a term and its reported percentage. The registry record does not give further detail about the event or its outcome.
The safety denominator is 69, whereas the registry enrollment is 71. The record does not explain this difference. The figures should not be converted into a comparative risk or generalized beyond the study population based on the information reported. Zero deaths means no deaths are listed in this safety summary; it does not establish the absence of all possible risks.
12. What the Result Does, and Does Not, Mean
The study is designed to describe hSBA antibody measurements and safety observations after a single MenQuadfi® booster in toddlers who had been primed in infancy with Nimenrix® or Menveo®. It identifies a laboratory endpoint, a threshold, four serogroups, two assessment times, and the analysis population intended for the primary endpoint. These details clarify what the study set out to measure.
The posted record does not report the primary endpoint percentages or 95% confidence interval limits. It therefore does not show the numerical antibody results or their precision. The record cannot support a numerical conclusion about the proportion meeting the stated threshold at either assessment time. The absence of those results in the registry record should not be interpreted as a value of zero or as evidence of no change.
The study has no comparison group. Even if before-and-after endpoint values were available, a single-group description would not isolate the effect of the booster from other possible explanations for observed changes. The registry does not report a controlled efficacy comparison or disease outcomes. Its description of the study context does not turn an antibody measurement into a direct measure of clinical protection.
The safety summary records 1 serious adverse event among 69 at risk, 45 other adverse events among 69 at risk, and 0 deaths; febrile convulsion is listed as the top serious term at 1.4%. These observations are useful as descriptions of events recorded in the study, but the study has no control group for interpreting relative safety. The record does not establish whether an event was caused by vaccination.
Accordingly, the posted record supports an understanding of the study question and design, along with a limited description of safety counts. It does not provide the central numerical immunogenicity results, the precision of those results, or evidence from a randomized comparison. The registry record does not report the sample-size rationale, detailed statistical analysis plan, or missing-data methods, so those aspects of the strength and limitations of the evidence remain uncertain.
13. Why This Trial Matters Statistically
This study is statistically informative because it illustrates the distinction between a clearly defined endpoint and a fully interpretable result. The registry specifies an hSBA threshold, the four serogroups, assessment times, and a 95% confidence interval as the dispersion measure. Those definitions indicate what the primary outcome is meant to summarize. But without the percentages, interval limits, and denominators, readers cannot assess the observed levels or the precision of the estimates.
Its single-arm design also makes the interpretation boundary especially important. Measurements at Day 1 and Day 31 can describe observations over time in the study group, but there is no concurrent control group to support a like-for-like comparison. Statistical methods cannot recover a randomized contrast that the design did not include. This is a general feature of single-group descriptive studies, not a judgment about the study’s conduct.
The difference between registry enrollment and the safety denominator, alongside the defined full and per-protocol analysis populations, highlights why denominator reporting and participant flow matter. In general, a percentage is only interpretable when readers know who was eligible for that analysis and how many contributed data. The registry record does not provide the endpoint-specific denominators or a complete account of missing measurements.
The safety summary likewise demonstrates the limits of counts without a comparator or causal assessment. Event counts describe what was recorded in the study, while comparative safety questions require a suitable comparison and appropriately reported analyses. The posted record permits a concise description of the reported safety entries, but not a relative-risk conclusion.
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.
A key limitation for interpreting the registry record is that the primary endpoint values are not reported. The record identifies the endpoint definition and confidence-interval type but gives neither the percentages nor the interval limits. Endpoint-specific denominators and counts are also not reported. As a result, the magnitude and precision of the primary immunogenicity findings cannot be evaluated from the posted results.
The single-arm design has no control group, and the study is open-label. Before-and-after measurements can describe observations across the scheduled assessments but do not provide a controlled estimate of the booster’s effect. The registry does not report clinical disease outcomes as the primary endpoint, so the laboratory measure should not be read as a direct record of disease prevention.
The record lists enrollment of 71 but safety figures use 69 participants at risk. It does not explain the difference or provide a complete participant flow. The primary endpoint is described for a per-protocol subset of the full analysis set, with reporting limited to participants with data for each serogroup. The full per-protocol criteria, endpoint-specific denominators, and extent or reasons for missing data are not reported in the registry record.
The registry also does not report a detailed statistical analysis plan, the method used to calculate confidence intervals, a multiplicity strategy, or missing-data sensitivity analyses. It does not report the rationale for the enrollment target. Planning illustrations are described as hypothetical two-arm calculations and should not be read as the design or as observed power for this single-arm study. These limitations concern what can be concluded from the registry record; they do not establish what analyses may have been conducted elsewhere.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of Immunogenicity and Safety of MenQuadfi® as a Booster Vaccine in Toddlers 12 to 23 Months, Regardless of the Quadrivalent Meningococcal Conjugate Vaccine Used for Priming in Infancy — NCT05929651.
- Registry record last updated 2025-09-22; status last verified 2025-08.
- Results first posted 2025-09-22.
- 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 a completed, Phase IV, descriptive, open-label, single-arm, multi-center study in healthy toddlers 12 to 23 months of age in Argentina. Participants had received at least 1 dose of Nimenrix® or Menveo® during infancy and received a single MenQuadfi® booster. Enrollment is listed as 71. The study included blood sampling before vaccination on Day 1 and on Day 31, 30 days after vaccination, with a safety telephone call on Day 9.
The primary endpoint is the percentage with hSBA titers >=1:8 against serogroups A, C, Y, and W, reported for the per-protocol analysis set with 95% confidence intervals. The registry record does not report those percentages or interval limits. Safety entries list 1 serious adverse event among 69 at risk, 45 participants with other adverse events among 69 at risk, and 0 deaths; febrile convulsion is the top serious term at 1.4%. No comparator is reported.