Mucosal Immunity Against Neisseria Gonorrhoeae After 4CMenB Vaccination: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Mucosal Immunity Against Neisseria Gonorrhoeae After 4CMenB Vaccination (NCT04722003), a randomized phase 2 study. The primary outcome is Geometric Mean of Percentage of Total IgG in Rectal Mucosal Specimens Against OMV Ng 1291 Antigens.

2. Clinical Question

This is a mechanistic immunogenicity question: it concerns a measured antibody response in rectal mucosal specimens, rather than a reported clinical gonorrhoea outcome. The registry lists measurement at Day 1, 29, 43, 57, and 181. The objective was to characterize the mucosal IgG response elicited by 4CMenB relative to saline placebo in healthy adult subjects. The outcome description specifies an ELISA measurement and a geometric mean for each treatment group at the listed visits.

The trial also lists serum IgG responses to OMV Ng1291 and CNG20 antigens, reactogenicity, and serious adverse events among its secondary outcomes. Those are distinct from the primary rectal mucosal endpoint. The registry record does not report numerical results for the primary or secondary outcomes, nor a statistical comparison of treatment groups. Therefore, the clinical question can be described from the design and outcome definitions, but the posted record does not establish the size or precision of any between-group difference.

3. Trial Design

The registry describes NCT04722003 as a completed, randomized, triple-masked, parallel-group Phase 2 trial sponsored by the National Institute of Allergy and Infectious Diseases. Its title concerns mucosal immunity against Neisseria gonorrhoeae after 4CMenB vaccination. The recorded enrollment is 52. The brief summary describes approximately 50 participants and a planned allocation of approximately 40 to 4CMenB and 10 to placebo; the arm descriptions list N=40 and N=10. These are planning descriptions and should not be treated as the numbers included in each outcome analysis. The registry separately reports 41 and 11 participants at risk for the serious-adverse-event summaries.

Participants received two doses of their assigned injection on Day 1 and Day 29. The 4CMenB and saline placebo were administered intramuscularly into the deltoid muscle of the preferred arm. The brief summary describes enrollment stratified by sex and treatment arm. During enrollment of the biopsy cohort, male and non-pregnant female subjects were to be randomized 4:1, up to a maximum of 10 male and 10 non-pregnant female subjects. The registry describes one US site, participant ages 18–49, and an estimated participation duration of approximately 8 months. The listed study start was 2021-11-01, primary completion was 2023-10-02, and status is completed.

The stated primary objective was to characterize rectal mucosal IgG responses to gonorrhoea-related antigens in the 4CMenB group compared with placebo. Randomization supports a treatment-group comparison by allocating participants through chance, while masking is intended to limit the influence of treatment knowledge on trial conduct or assessment. The registry identifies the trial as triple-masked but does not specify which groups of people were masked. Further details of sequence generation, concealment, and implementation are not reported in the registry record.

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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The immunogenicity population included all participants who received at least one dose of study vaccine and contributed at least one sample for immunogenicity testing for which valid results were reported. Visit-specific summaries were limited to participants in the immunogenicity population with data available at the respective visit.

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.

6. Primary Endpoint

The registry lists the primary outcome as Geometric Mean of Percentage of Total IgG in Rectal Mucosal Specimens Against OMV Ng 1291 Antigens, measured over Day 1, 29, 43, 57, and 181..

The primary endpoint is the geometric mean of the percentage of total IgG in rectal mucosal specimens against OMV Ng 1291 antigens. The specimen type and antigen target make the endpoint specific to a local mucosal antibody response; it is not a direct measure of gonorrhoea infection, disease, or prevention. The assay is listed as ELISA. The endpoint was scheduled for assessment at Day 1, 29, 43, 57, and 181.

A geometric mean is a way to summarize measurements that are positive and may vary multiplicatively. In general, it is calculated by transforming observations to a logarithmic scale, taking an arithmetic mean on that scale, and transforming back. This can make a geometric mean more suitable than an arithmetic mean when values are right-skewed or differences are naturally interpreted as relative changes. The registry specifies a geometric mean and a 95% confidence interval, but does not report the observed endpoint values or the specific calculation details.

Using the percentage of total IgG expresses antigen-specific antibody in relation to the total IgG measured in the specimen. This can help characterize the composition of the local antibody response rather than only its absolute amount. Interpretation still depends on collection, assay performance, and the analysis population. The registry record does not give the assay’s detection limits, handling of values outside measurable limits, or a clinically meaningful threshold. The endpoint therefore describes an immunologic measurement, and its clinical significance cannot be determined from the endpoint definition alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a geometric mean summarize?

In general, the geometric mean summarizes positive measurements by averaging them after logarithmic transformation and then returning the result to the original scale. This approach is often useful when measurements vary multiplicatively or have a long right tail. It differs from the arithmetic mean, which averages the original values directly. Neither summary is automatically preferable in every setting; the choice should fit the measurement and the planned scientific question.

For this trial, the registry specifies a geometric mean for the percentage of total IgG in rectal mucosal specimens against OMV Ng 1291 antigens. It also specifies a 95% confidence interval. The record does not provide observed means, interval limits, or full computational details, so it is not possible to assess the numerical estimates or verify which specific estimation procedure was used.

How should a confidence interval be read?

In general, a confidence interval communicates uncertainty in an estimate under a statistical procedure and its assumptions. It is not a range containing a fixed proportion of individual participant measurements, and it does not by itself describe clinical importance. The interval’s width provides information about precision: estimates based on more information may be more precise, while variability and missing measurements can also affect precision. The registry record lists a 95% confidence interval as the endpoint’s dispersion measure, but does not report its endpoints.

A confidence interval for a group’s geometric mean is not the same as a confidence interval for the difference between groups. To quantify the treatment comparison, an analysis would generally need to estimate a contrast, such as a difference or ratio, and report uncertainty for that contrast. The registry record does not report such a contrast or its interval. No treatment-comparison test or p-value is listed.

Why do the scheduled visits matter?

The endpoint is scheduled at Day 1, 29, 43, 57, and 181. Repeated observations can describe response over time, but they also create an analysis choice: investigators may compare groups at a selected visit, estimate change from an earlier measurement, or use a model that accounts for the pattern of measurements within each participant. These approaches answer different questions and can make different assumptions. The registry record does not identify which repeated-measures method, if any, was used.

Measurements from the same participant are generally related rather than independent. In general, a repeated-measures model can account for that within-participant relationship while estimating group patterns over time. The suitability of a model depends on the outcome distribution, timing, missingness, and assumptions about the correlation structure. The record does not report a model specification, covariance structure, transformation rules, or diagnostics. It would therefore be inappropriate to attribute any particular repeated-measures method to this trial.

What is the role of randomization and masking?

Randomization is intended to make treatment assignment independent of participant characteristics on average, reducing systematic differences between groups at baseline. In a small trial, randomization does not guarantee that every characteristic will be balanced. The registry says allocation was randomized and enrollment was stratified by sex and treatment arm, but does not report the randomization sequence method, allocation concealment procedure, or baseline balance for the immunogenicity population.

Masking can reduce the risk that expectations influence participant reports, treatment delivery, or outcome assessment. The registry labels the trial triple-masked. The identities of the masked groups and any procedures for maintaining or breaking the mask are not reported in the registry record. Thus, the masking designation describes the recorded design, but does not provide enough detail to assess its implementation.

Why can over-dispersion matter?

In general, over-dispersion occurs when the observed variability exceeds what a statistical model expects. If an analysis assumes too little variability, standard errors may be too small and confidence intervals may be too narrow. Models for counts or proportions often need particular attention to dispersion; an analysis of transformed antibody measurements has different distributional considerations. The registry record does not report an over-dispersion assessment or a statistical model for the primary endpoint, so no trial-specific conclusion about over-dispersion can be made.

What can planning calculations tell readers?

The registry’s sample-size assumptions describe illustrations using a two-sided significance level of 0.05, equal allocation, and a normal approximation. They define the effect to detect as a stated fraction of the observed effect. Such calculations are planning illustrations: they indicate what sample size might be associated with chosen assumptions, not the probability that this completed trial found a true effect. They are not observed power. The registry record does not report the trial’s own sample-size justification, the numerical illustration values, or the observed endpoint effect needed to interpret those illustrations.

Planning calculations are sensitive to the assumed effect size, variability, allocation, and analysis method. When these assumptions differ from the trial’s actual design or data, the resulting sample-size illustration may not describe the trial’s operating characteristics. The registry’s stated equal-allocation assumption also differs from the planned approximate 4:1 allocation described for the intervention and placebo groups. No reconciliation or trial-specific power calculation is reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The primary endpoint is assessed at Day 1, 29, 43, 57, and 181, and the registry lists six outcome measures in total. It also names secondary outcomes involving serum IgG responses to OMV Ng1291 and CNG20 antigens, reactogenicity, and serious adverse events. Multiple visits and outcomes create multiple opportunities for statistical comparisons. In general, a multiplicity plan specifies which comparisons are primary and how the analysis will account for the increased chance of a false-positive finding when several hypotheses are tested.

The registry record does not report a multiplicity adjustment, a testing hierarchy, or a prespecified rule identifying which visit or contrast would carry the main inferential conclusion. It also does not report analyses: the analysis count is zero. Without posted tests or a documented analysis plan, it is not possible to determine whether multiplicity was addressed by adjustment, outcome hierarchy, or another approach. No p-values or estimates are listed for the primary or secondary outcomes.

The immunogenicity population is defined as participants who received at least one dose and contributed at least one sample with valid immunogenicity results. Visit-specific summaries were limited to participants in that population with additional visit-specific information, but the full description is not reported in the registry record. The record does not say how missing samples, invalid assay results, measurements below or above assay limits, or withdrawals were handled. It also does not report imputation, sensitivity analyses, or whether analyses followed assignment regardless of received treatment.

These omissions matter because available measurements may not represent all randomized participants, especially when inclusion depends on valid samples. The number randomized, the number with at least one usable sample, and the number contributing at each visit can differ. The registry reports enrollment and separate safety denominators, but not the visit-specific immunogenicity denominators needed to assess missingness or attrition for the primary endpoint.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry’s serious-adverse-event summary lists 4CMenB with 41 participants at risk and 0 participants affected, and placebo with 11 participants at risk and 0 participants affected. Deaths are recorded as 0 in both groups. The record lists no top serious-event terms. These are the posted serious-event counts; they do not provide event descriptions or additional detail about timing or duration.

The separate other-adverse-event figures are 41 affected among 41 at risk in the 4CMenB group and 8 affected among 11 at risk in the placebo group. These counts should be kept distinct from the serious-adverse-event figures. The registry summary does not identify the specific events represented by these other-event counts, their severity, or their relationship to study injections. The listed secondary outcomes include reactogenicity, but the record does not provide detailed reactogenicity results.

Zero recorded serious events in these groups does not establish that serious events are impossible or that no unrecorded events occurred. Safety counts describe what was recorded for the participants at risk within the registry summary. The denominators are not the same as the planned group sizes described in the trial summary, and they do not establish the number contributing valid primary endpoint samples. The figures describe reported observations only and do not support treatment advice or a broader safety conclusion.

12. What the Result Does, and Does Not, Mean

The registry record describes a randomized comparison of 4CMenB with saline placebo, with a primary measure of rectal mucosal IgG against OMV Ng 1291 antigens. It specifies a geometric mean, a 95% confidence interval, and collection at multiple visits. These details identify what the investigators intended to measure and the broad structure of the comparison.

The record does not report the observed primary endpoint values, between-group estimates, confidence interval limits, or statistical tests. It therefore does not show whether the response was higher, lower, or similar between groups, nor how precisely any difference was estimated. The same limitation applies to the named secondary outcomes: their definitions are listed, but numerical results are not reported in the registry record.

The endpoint is an immunologic measurement, not a clinical outcome such as diagnosed gonorrhoea. Even if numerical antibody differences were available, their meaning would depend on the size and uncertainty of the difference, the measurement properties, and the relationship between the immune marker and clinical outcomes. The registry record does not report a threshold for a meaningful response or evidence that connects this endpoint to prevention of infection.

The planned sample-size illustrations are not a substitute for results or observed power. They are based on assumptions and an effect scaled to the observed effect, while the registry record does not report the effect values or illustration outputs. Similarly, the safety summaries describe recorded counts and should not be read as comprehensive evidence of risk beyond the participants and events represented in those summaries.

Accordingly, the record supports a description of the trial question, design, outcome definition, and reported serious-event counts. It does not support a conclusion about the magnitude or clinical importance of the vaccine-associated immune response, the comparative performance of the groups, or the clinical effect of vaccination on gonorrhoea.

13. Why This Trial Matters Statistically

This trial illustrates why an endpoint definition and an endpoint result are different kinds of information. The registry precisely identifies a mucosal antibody measurement, its antigen target, summary scale, uncertainty measure, and collection schedule. Those details help clarify the scientific question, but without estimates and uncertainty intervals they cannot answer how the groups compared.

It also shows why the analysis population and denominators matter. Planned group sizes, total enrollment, safety participants at risk, and participants with valid immunogenicity samples refer to different quantities. A complete statistical interpretation needs the denominator for each outcome and visit, along with clear reporting of how participants with missing or invalid measurements were treated.

Repeated measurements raise important design and analysis questions. A response measured at several visits may be interpreted as a pattern over time or as a comparison at a designated visit. Those choices should be tied to a clear primary estimand and analysis plan. The registry record does not report that plan or the analyses, so the intended treatment contrast cannot be fully reconstructed from the outcome definition alone.

Finally, the distinction between immunologic and clinical outcomes is important. A mucosal IgG endpoint can characterize a biological response, while a clinical claim would require evidence about clinical outcomes and their uncertainty. Statistical reporting should keep those interpretations separate. The registry record’s lack of posted endpoint results makes this trial a useful example of the limits of design information when outcome estimates are unavailable.

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 principal limitation for interpretation is that numerical immunogenicity results and statistical analyses are not reported in the registry record. The primary endpoint is defined, but its group estimates and 95% confidence intervals are absent. There is no reported treatment contrast, p-value, or model result from which to judge magnitude, direction, or precision.

The record gives an enrollment of 52, while its summary describes approximately 50 participants and approximate group sizes of 40 and 10. The serious-adverse-event summaries list 41 and 11 participants at risk. These figures are not interchangeable, and the record does not provide visit-specific immunogenicity denominators. The detailed eligibility text for visit-specific summaries is incomplete in the registry record.

Several analysis features are also unreported, including the statistical model, handling of repeated measurements, missing-data methods, assay-limit rules, multiplicity procedures, and the detailed masking and randomization procedures. The registry does not report a clinical threshold for interpreting the antibody endpoint, or a clinical outcome establishing how the biomarker relates to gonorrhoea. These gaps limit both reproducibility and the clinical interpretation of any potential immune response.

The registry describes a single US site and a selected population of healthy adults ages 18–49, including male and non-pregnant female subjects. The extent to which results would generalize beyond the enrolled population cannot be assessed without outcome data and fuller demographic and clinical descriptions. No claim about generalizability or clinical effect can be made from the design description alone.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Mucosal Immunity Against Neisseria Gonorrhoeae After 4CMenB Vaccination — NCT04722003.
• Registry record last updated 2026-10-21; status last verified 2026-06-22.
• Results first posted 2024-11-05.
• 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.

18. Record Summary

NCT04722003 is a completed, randomized, triple-masked, parallel-group Phase 2 trial sponsored by the National Institute of Allergy and Infectious Diseases. It compared two doses of 4CMenB with two saline placebo injections in healthy adults ages 18–49. Recorded enrollment was 52, and the listed primary objective concerned rectal mucosal IgG response to Neisseria gonorrhoeae-related antigens.

The primary endpoint was the geometric mean percentage of total IgG in rectal mucosal specimens against OMV Ng 1291 antigens, measured by ELISA at Day 1, 29, 43, 57, and 181, with a 95% confidence interval specified. The record also lists serum antibody, reactogenicity, and serious-adverse-event outcomes.

Serious adverse events were recorded for 0 of 41 participants at risk in the 4CMenB group and 0 of 11 in the placebo group; deaths were 0 in both groups. Primary endpoint estimates, statistical comparisons, and analysis results are not reported in the registry record.