Safety and Efficacy of GSK Neisseria Gonorrhoeae GMMA (NgG) Investigational Vaccine When Administered to Healthy Adults 18 to 50 Years of Age: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Efficacy of GSK Neisseria Gonorrhoeae GMMA (NgG) Investigational Vaccine When Administered to Healthy Adults 18 to 50 Years of Age (NCT05630859), a randomized phase 1, phase 2 study. The primary outcome is Phase 1: Number of Participants Reporting Any Solicited Administration Site Events.

2. Clinical Question

3. Trial Design

This was a randomized, observer-blind, placebo-controlled, multi-country Phase 1/2 study. The registry record describes quadruple masking and a sequential model. Its stated aim was to evaluate safety and reactogenicity, demonstrate efficacy, and explore immunogenicity of the NgG investigational vaccine relative to placebo. The record lists GlaxoSmithKline as sponsor and gives the study status as completed.

The study enrolled 1009 participants. Its recorded start date is 2022-11-28, and its primary completion date is 2025-05-22. The registry record does not describe the countries, recruitment procedures, eligibility criteria beyond the healthy-adult description, or the allocation ratio.

In Phase 1, the dose groups received NgG 12.5 µg, 25 µg, or 50 µg; the comparison group received placebo. Each arm description specifies two doses, on Day 1 and Day 61. In Phase 2, the arms received the 50 µg highest tolerated dose, the 25 µg dose below the highest tolerated dose, or placebo, also in two doses on Day 1 and Day 61. The record says the Phase 2 dose choices were based on the safety evaluation performed in Phase 1.

The primary endpoint belongs to Phase 1 and concerns solicited administration-site events during the period from Day 1 to Day 7. Phase 2 secondary outcomes concern incidence rates of confirmed gonorrhea cases with and without Chlamydia trachomatis co-infection, and incidence rates of symptomatic and confirmed gonorrhea cases. Numerical results for these efficacy outcomes 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.

Before assignment: Phase 1 Placebo group: Enrollment in the Phase 1 portion of the study proceeded stepwise to allow three increasing dosages of the candidate vaccine to be tested against placebo. In this record we present the pooled Phase 1 placebo analysis group, which includes all participants who received placebo during Phase 1.

Only the first 6 of 7 groups are shown.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Analysis was performed on the Solicited Safety Set which includes all participants who received at least one dose of the study intervention and had solicited safety data available at the specified duration. Only participants from Phase 1 groups with solicited administration site events data available for the specified analysis at the specified duration were included in this outcome measure.

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.

Only the first 6 of 8 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Phase 1: Number of Participants Reporting Any Solicited Administration Site Events, measured over From Day 1 to Day 7.

The primary endpoint counts Phase 1 participants reporting any solicited administration-site event from Day 1 to Day 7. The events assessed were injection-site pain, erythema (redness), and swelling. “Any” means that the event is counted regardless of intensity grade. This is a participant count, not a count of how many separate episodes or symptoms each participant experienced.

Solicited events are actively assessed events specified in advance for collection. In general, this approach can make common, expected reactions easier to capture consistently than relying only on spontaneous reports. An administration-site endpoint focuses specifically on reactions at the injection site; it does not represent every safety outcome or establish an effect on gonorrhea incidence.

The endpoint is restricted to Phase 1, while the study also included Phase 2 efficacy outcomes. Its stated timeframe is short and begins on Day 1. The registry record does not report the number of participants with these events in each Phase 1 group, the corresponding comparison, or a measure of uncertainty. Without those results, the endpoint’s observed event frequency and the precision of a vaccine-placebo contrast cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count represent?

The primary outcome is a count of participants who reported any specified administration-site event during the stated assessment period. The event definition groups injection-site pain, redness, and swelling together, and includes events regardless of intensity grade. A participant with more than one of these symptoms is still counted as a participant reporting an event; the endpoint is not a total of symptom occurrences. This is a general explanation of how participant-count endpoints are interpreted.

The registry record describes a Solicited Safety Set for the primary assessment. It includes participants who received at least one dose and had solicited safety data available for the specified duration. The description also limits the analysis to Phase 1 groups with solicited administration-site-event data available. The record does not provide the resulting endpoint counts, the group denominators used for that endpoint, or further details about how incomplete assessments were handled.

How should group comparisons be understood?

In general, a randomized comparison estimates how an outcome differs between assigned groups under the study’s analysis approach. Randomization is intended to support comparability of groups, but it does not remove uncertainty from observed results or guarantee that every factor is balanced in a particular study. The record identifies the study as randomized and placebo-controlled but does not report the allocation ratio or the primary-endpoint comparison estimate.

For a binary outcome such as whether a participant experienced an event, analysts may report group counts and proportions, then compare groups using a chosen effect measure and statistical method. The method, estimated effect, and uncertainty all matter for interpretation. The registry record does not report the primary endpoint’s proportions, effect estimate, confidence interval, or test result. No recalculation is presented because the primary endpoint summary statistics needed for it are not reported.

What does a confidence interval explain?

As a general statistical concept, a confidence interval communicates the uncertainty around an estimated effect under a specified method. A narrower interval indicates greater precision than a wider interval, while an interval compatible with a range of effects may leave substantial ambiguity. A confidence interval does not establish that an effect is clinically important, and it does not correct for bias or missing data. No confidence interval for the primary endpoint or the listed safety counts is reported in the registry record.

Why does the event definition matter?

Combining pain, redness, and swelling into “any” gives a broad participant-level summary. It does not show which event contributed most, how intense events were, or whether participants experienced multiple event types. The record defines the endpoint as counting events regardless of intensity grade, but does not report component-specific results or intensity distributions. Those distinctions would be relevant to a fuller description of reactogenicity.

How should the safety counts be read?

The serious adverse-event entries pair an at-risk count with a count of participants affected. In general, these counts describe events recorded for the stated group; they do not, without further analysis, establish that the intervention caused an event. The registry record does not report a comparative statistical analysis, confidence intervals, follow-up duration for these entries, or event-level assessment of relationship to study intervention. The listed top serious terms each carry a reported 0.3% value, but the record does not connect those terms to a particular treatment group in the information available.

The adverse-event summary distinguishes serious adverse events from other adverse events and reports deaths separately. These categories should not be combined as though they were interchangeable outcomes. The record reports zero deaths in each listed group. It does not give enough detail to infer that no safety events occurred overall; the reported counts show that other adverse events were recorded in the groups.

What are planning calculations?

In general, sample-size planning calculations illustrate the number of participants or events a hypothetical future study might need under stated assumptions. The planning description associated with the analysis specifies 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 the observed effect. Such illustrations are not observed power and are not evidence that the original study was designed around those assumptions. The registry record does not report the trial’s own sample-size justification or statistical design calculations.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 23 outcome measures and 8 analyses. The primary endpoint is one measure, while the listed secondary outcomes include incidence rates for confirmed gonorrhea with and without Chlamydia trachomatis co-infection and incidence rates for symptomatic and confirmed gonorrhea. The record does not report how these outcomes were ordered for statistical testing or whether any formal multiplicity adjustment was planned or used.

Multiplicity is a general statistical concern when several outcomes, comparisons, time points, or subgroup analyses are examined. The more questions assessed, the more important it is to know whether analyses were prespecified and how interpretation accounted for the number of tests. The number of listed measures and analyses alone does not show which results were confirmatory or whether adjustment was appropriate.

Missing-data handling is not reported in the registry record. For the primary analysis, the described Solicited Safety Set includes participants who received at least one dose and had solicited safety data available for the specified duration. The record does not say how missing diary entries, partial follow-up, or unavailable event assessments were treated, or whether any sensitivity analyses assessed the effect of missing information.

The record also does not report the full statistical analysis plan, interim analyses, or the analysis populations used for the Phase 2 efficacy outcomes. These omissions limit assessment of prespecification, selective reporting, and the impact of missing outcome data. They do not establish that such procedures were absent; their details are not reported in the registry record.

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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: syncope (0.3%), renal failure (0.3%), haematoma (0.3%), anal fistula (0.3%), food poisoning (0.3%).

The serious adverse-event figures are participant counts, shown alongside the number at risk in each group. In Phase 1, 0 of 6 participants are listed as affected in each of the 12.5 µg, 25 µg, and 50 µg groups and in placebo. In Phase 2, the corresponding figures are 3 of 329 for the 50 µg group, 11 of 327 for the 25 µg group, and 3 of 324 for placebo. The record lists zero deaths in every group.

These counts are descriptive. They do not by themselves show whether an event was caused by the intervention, whether groups differ beyond chance, or how precisely any difference is estimated. The registry record does not report confidence intervals, a comparative analysis, or the relationship of these events to the intervention. The small Phase 1 at-risk counts mean the listed counts should be read in the context of those group sizes, not as a complete characterization of safety.

The registry record lists Syncope, Renal failure, Haematoma, Anal fistula, Food poisoning, and Cholecystitis among the top serious terms, each with a reported 0.3% value. It does not identify the group associated with each term in the recorded information. These term listings and percentages should not be treated as rates for a particular arm without that information.

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

The registry record describes a completed randomized Phase 1/2 investigation of the NgG vaccine, with different dose groups in Phase 1 and two selected dose levels in Phase 2. It identifies a Phase 1 primary endpoint based on solicited administration-site events and Phase 2 secondary outcomes based on gonorrhea incidence. It also reports serious and other adverse-event counts by group.

However, the primary endpoint’s numerical results are not reported in the registry record. The available record therefore cannot show the frequency of solicited administration-site events by Phase 1 group, the size of any difference from placebo, or the precision of that comparison. Numerical results for the listed Phase 2 efficacy outcomes are also not reported. The study’s aim to demonstrate efficacy and explore immunogenicity is not itself evidence that those aims were met; immunogenicity results are not included in the record.

The serious adverse-event counts are descriptive safety information, not proof of cause or a formal comparison. The listed counts do not alone establish whether a treatment effect exists, and the record does not report uncertainty estimates or a statistical test for these figures. The broader other-adverse-event counts are a separate category and should not be substituted for the solicited primary endpoint.

In general, a clinical-trial result is interpreted using the outcome definition, analysis population, effect estimate, uncertainty, and study conduct together. The registry record leaves important elements unavailable, including the primary endpoint result, efficacy estimates, and details of missing-data handling and multiplicity. Accordingly, the available information supports a description of the trial design and recorded safety counts, but not a conclusion about efficacy or a definitive comparative safety assessment.

13. Why This Trial Matters Statistically

The study is statistically notable for its sequential Phase 1/2 structure. The arm descriptions state that Phase 1 evaluated three NgG dose levels and placebo, and that Phase 2 used the 50 µg highest tolerated dose and the 25 µg dose below it, selected based on the Phase 1 safety evaluation. This makes the relation between dose selection and phase structure important when considering how the study’s questions were addressed.

The primary outcome is a participant-level safety measure, while the Phase 2 secondary outcomes concern gonorrhea incidence. These outcomes answer different questions and should not be collapsed into a single claim. A short-term solicited administration-site endpoint does not itself answer whether gonorrhea incidence differed, and incidence outcomes do not substitute for detailed assessment of reactogenicity.

From a statistical perspective, the record illustrates why outcome definitions, analysis populations, uncertainty estimates, and prespecified testing plans matter. The primary endpoint is clearly described, but its numerical results are not reported in the registry record. The record lists 23 outcome measures and 8 analyses, yet does not report the multiplicity approach. It also does not report the trial’s sample-size justification or full statistical plan. These omissions constrain independent assessment of the strength and precision of the findings.

The listed safety counts provide useful descriptive context across the dose groups and placebo groups, but they are not a substitute for comparative estimates with uncertainty. The record’s details permit careful description of trial structure and recorded counts while also making clear where conclusions cannot be drawn from the reported information.

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 interpreting the primary question is that the registry record does not report the primary endpoint results. It gives the outcome definition and analysis population description, but not the participant counts by group, the denominators used for that endpoint, an effect estimate, or a measure of uncertainty. The primary comparison therefore cannot be independently evaluated from the registry record.

Numerical results for the Phase 2 gonorrhea outcomes are also not reported. The record does not provide incidence estimates, comparison results, or precision measures for confirmed cases, symptomatic cases, or co-infection categories. Immunogenicity results are not reported in the information described.

The safety summary includes group counts for serious and other adverse events, but the registry record does not provide a comparative analysis or uncertainty estimates. It does not report the relationship of serious events to the intervention or the group attribution for the listed top serious terms. The record also does not specify the follow-up period for the adverse-event summary in the information available.

Other methodological details are unavailable, including the sample-size justification, full statistical analysis plan, multiplicity procedures, missing-data methods, allocation ratio, and interim-analysis information. The primary analysis population description indicates that participants needed available solicited safety data, but the handling of incomplete assessments is not reported. These limitations do not demonstrate that analyses or safeguards were absent; they mean their details cannot be assessed from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Safety and Efficacy of GSK Neisseria Gonorrhoeae GMMA (NgG) Investigational Vaccine When Administered to Healthy Adults 18 to 50 Years of Age — NCT05630859.
• Registry record last updated 2026-06-16; status last verified 2026-05.
• Results first posted 2026-06-16.
• 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

The registry record identifies NCT05630859 as a completed, randomized, observer-blind, placebo-controlled, multi-country Phase 1/2 study of the NgG investigational vaccine in healthy adults 18 to 50 years of age. It lists enrollment of 1009, quadruple masking, and a sequential model. The recorded start date is 2022-11-28, and the primary completion date is 2025-05-22.

Phase 1 assessed NgG 12.5 µg, 25 µg, and 50 µg against placebo. Phase 2 assessed 50 µg, 25 µg, and placebo. The primary endpoint was Phase 1 participants reporting any solicited administration-site event from Day 1 to Day 7. Its numerical results are not reported in the registry record. Phase 2 efficacy outcomes are listed, but numerical results are not reported.

Group-specific serious and other adverse-event counts and zero deaths are reported. These are descriptive figures; comparative estimates, uncertainty measures, and several analysis details are not reported in the registry record.