Extension Study of the Efficacy of the GSK 580299 Vaccine in Japanese Women Vaccinated in the Primary NCT00316693 Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Extension Study of the Efficacy of the GSK 580299 Vaccine in Japanese Women Vaccinated in the Primary NCT00316693 Study (NCT00929526), a randomized phase 3 study. The primary outcome is Number of Subjects Reporting Histopathologically Confirmed Cervical Intraepithelial Neoplasia (CIN)1+ Cases Associated With HPV16 and/or HPV18 Detected Within the Lesional Component of the Cervical Tissue Specimen..

2. Clinical Question

3. Trial Design

This is a Phase 3, randomized, parallel-group extension study with no masking. The registry lists enrollment as 752. It describes the groups by the vaccine participants received in the primary vaccination study, NCT00316693: 3 doses of Cervarix™ or 3 doses of Aimmugen™. The extension therefore concerns follow-up of participants from that earlier study; the registry record does not describe a new vaccination intervention in the extension.

The extension was intended to assess cervical intraepithelial neoplasia lesions, cervical cancer, and cytological abnormalities associated with HPV-16 and/or HPV-18 or other oncogenic HPV types. Safety and persistence of the humoral immune response were also to be evaluated. The record describes follow-up for up to 48 months after administration of the first vaccine dose. It says this protocol posting covers extension objectives and outcome measures at Months 36 and 48; the objectives and outcome measures of the primary phase are presented in a separate protocol posting.

The listed extension procedures are liquid-based cytology sampling and blood sampling. The registry gives a study start of 2009-06, primary completion of 2011-02, and status of completed. These record-level details do not establish how many participants completed follow-up or contributed data to each endpoint. The randomization method, concealment procedures, visit schedule beyond the stated time references, and analysis plan are not reported in the registry record.

There is an important timing ambiguity for interpretation. The primary endpoint is described as covering Month 0 up to Month 12, while the extension description emphasizes Month 36 and Month 48. The registry record does not explain how the primary endpoint timeframe relates to the extension assessments. It is therefore not possible to infer the timing of an endpoint comparison from the general extension description alone.

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: Subjects were randomised in the primary vaccination study NCT00316693 to receive the Cervarix vaccine or the Aimmugen vaccine and were aged 20 - 25 years at the time of first vaccination. Only subjects showing willingness to participate in this long term follow-up study and who had signed the informed consent form entered this study.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The analysis was performed in subjects who were seronegative at baseline and negative for human papillomavirus (HPV) desoxyribonucleic acid (DNA) at baseline and Month 6 in the primary study (NCT00316693) for the HPV-type considered and for whom data concerning efficacy outcome measures were available in this follow-up study.

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 Number of Subjects Reporting Histopathologically Confirmed Cervical Intraepithelial Neoplasia (CIN)1+ Cases Associated With HPV16 and/or HPV18 Detected Within the Lesional Component of the Cervical Tissue Specimen., measured over From Month 0 up to Month 12.

The primary endpoint is a count of participants with histopathologically confirmed CIN1+ cases associated with HPV16 and/or HPV18, with the relevant HPV type detected within the lesional component of the cervical tissue specimen. CIN1+ includes CIN1, CIN2, CIN3, adenocarcinoma in situ, and invasive cervical cancer. Detection of HPV types 16 or 18 is described as being made by polymerase chain reaction.

The endpoint population is defined using infection and antibody status in the primary study. For a single HPV type, participants were required to be DNA negative at Month 0 and Month 6 and seronegative at Month 0 for the corresponding type. For combined types, the definition requires DNA negativity at Month 0 and Month 6 and seronegativity at Month 0 for at least one HPV type. The registry also specifies that efficacy outcome data must be available.

In general, a histopathological endpoint uses examination of tissue to classify a lesion, while HPV detection links the lesion to the virus type of interest. Counting participants with a qualifying case gives a binary participant-level outcome: each person either meets the endpoint definition or does not. This kind of endpoint can describe the occurrence of defined lesions, but its interpretation depends on the stated eligibility, detection, and follow-up rules. The registry record gives no primary-endpoint group counts or effect estimate, and its Month 0 up to Month 12 timeframe is not reconciled with the extension’s stated Month 36 and Month 48 assessments.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General: the design labels describe different features of a trial. Randomized means group assignment is described as random, but does not reveal the sequence-generation method or whether assignment was concealed. Parallel means the groups are followed as separate groups rather than crossing participants between interventions. No masking means the record does not describe blinding. These labels alone do not establish how consistently the study procedures were carried out or whether outcome assessment could be influenced by knowledge of group assignment.

What does a count endpoint represent?

The primary outcome is the number of participants meeting a defined case criterion. The criterion combines histopathological confirmation of CIN1+ with detection of HPV16 and/or HPV18 in the lesional tissue component. General: a count endpoint is usually interpreted in relation to the number of participants eligible for and assessed for that outcome. Counts without those denominators do not show how frequently the endpoint occurred in each group. The registry record does not report the primary outcome counts or endpoint-specific denominators.

General: binary outcomes can be compared using measures such as a risk difference, risk ratio, or odds ratio, depending on the analysis plan and data structure. These measures answer different questions and should be accompanied by uncertainty estimates. No such primary-endpoint comparison is reported in the registry record, so none can be interpreted for this study from the posted efficacy information.

Why do the endpoint rules matter?

The HPV status rules define which participants are included in the primary endpoint population. They require negative DNA tests at specified primary-study visits and seronegativity at baseline for the relevant type or at least one type in the combined definition. General: restricting an analysis to a biologically defined population can make the research question more specific, but it also means that the result applies to that defined population rather than automatically to everyone enrolled. The registry record does not state how many participants satisfied the endpoint population definition or how missing test results were handled.

Histopathological confirmation and PCR detection are distinct components of the endpoint definition: one establishes the qualifying lesion, and the other establishes detection of the relevant HPV type. General: composite case rules can be informative, but their interpretation depends on consistent measurement and on how each component is handled. The registry record does not report additional laboratory or pathology quality-control procedures.

What can be concluded from the reported design?

The record identifies a Phase 3 randomized parallel-group study and no masking. It does not report the randomization method, allocation concealment, an adjustment strategy, or the statistical model for efficacy outcomes. These details are not reported in the registry record. Consequently, the design labels should not be treated as a complete statistical analysis plan.

General: confidence intervals are used to express uncertainty around an estimate. Their width depends on the amount and distribution of information as well as the analysis method. A p-value is calculated relative to a statistical model and a null hypothesis; it is not a measure of the probability that a treatment effect is true. Since no primary-endpoint estimates, intervals, or tests are reported, these concepts explain how such results would be read but do not provide a result for this study.

The registry lists a sample-size planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Its effect to detect is described as a stated fraction of the observed effect. General: planning calculations estimate the amount of information needed under chosen assumptions; they are not results from the enrolled participants and are not observed power. The registry record does not report a trial-specific sample-size justification, and no numerical planning illustration is stated in the record.

How should multiple outcomes be considered?

The extension includes several efficacy and immune-response outcome areas, and the registry states that there are 15 outcome measures. General: when many outcomes or time points are examined, the chance of at least one apparently unusual result can increase if each is tested separately. Methods such as prespecifying a primary comparison or adjusting for multiple testing can address particular multiplicity concerns, but the appropriate approach depends on the planned questions. The multiplicity strategy is not reported in the registry record. With no analyses posted, there are no reported findings from which to assess the consequences of multiple testing.

10. Multiplicity, Missing Data and Analysis Populations

The registry describes 15 outcome measures, spanning cervical lesions and cytological abnormalities, incident and persistent cervical infection, and antibody titres, among other specified outcomes. It does not report an efficacy analysis for any of them. The multiplicity approach—such as a hierarchy among outcomes or an adjustment for repeated testing—is not reported in the registry record. General: when several outcomes and time points are assessed, interpreting isolated p-values without knowing the prespecified testing strategy can be misleading. No multiplicity-adjusted or unadjusted efficacy results are available in the record.

The primary endpoint population is defined by baseline serology, HPV DNA results at baseline and Month 6 in the primary study, HPV type, and availability of efficacy outcome data. The number meeting those criteria is not reported in the registry record. The record does not explain how missing specimens, missed visits, incomplete tissue assessments, or other missing endpoint information were handled. It also does not report whether analyses used an intention-to-treat, per-protocol, or other analysis population.

General: missing data can affect both the number of participants contributing to an analysis and the assumptions needed to interpret it. If participants with unavailable outcomes differ from those with observed outcomes, a complete-case analysis may not represent the full eligible group. The direction and size of any resulting bias cannot be determined without information about missingness and the analytic approach.

The extension description refers to Months 36 and 48, whereas the primary endpoint timeframe is listed as Month 0 up to Month 12. The record does not explain how this timing relates to the primary endpoint analysis. Interim analyses, stopping rules, and the statistical plan are not reported in the registry record.

11. Safety Results

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

Other (non-serious) adverse events

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

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: abortion missed (0.8%), premature separation of placenta (0.5%), foetal distress syndrome (0.5%), abortion spontaneous complete (0.3%), allergic granulomatous angiitis (0.3%).

The registry reports serious adverse event figures by group: the Cervarix Group has 11 participants with events among 375 at risk, and the Aimmugen Group has 16 among 377 at risk. These are safety counts, not efficacy results. They should be read with the registry’s group labels and at-risk counts, rather than treated as a comparison of cervical lesions or HPV infection.

The record also lists serious adverse event terms with percentages: Abortion missed, 0.8%; Premature separation of placenta, 0.5%; Foetal distress syndrome, 0.5%; Abortion spontaneous complete, 0.3%; Allergic granulomatous angiitis, 0.3%; and Borderline personality disorder, 0.3%. The listing does not specify the group attribution or denominator for these percentages, so they cannot be assigned to a particular group or used to calculate group-specific rates from the registry record. It also does not provide event narratives or timing in relation to vaccination or follow-up.

General: safety counts summarize reported events under the registry’s collection and coding procedures; they do not by themselves establish that an event was caused by a vaccine. The record lists no death counts. Death information is not reported in the registry record. The figures should therefore be interpreted as reported safety information, with the stated limits on context, rather than as evidence of causality or comparative safety.

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

The registry record establishes that this was a completed Phase 3 randomized extension study in Japanese women who had participated in a primary vaccination study. It identifies two groups based on the vaccine received in that primary study, describes the intended follow-up, and specifies a primary endpoint involving histopathologically confirmed CIN1+ associated with HPV16 and/or HPV18. It also records selected serious adverse event information.

It does not report the primary endpoint counts, an efficacy estimate, a confidence interval, or a statistical test. Therefore, the record does not support a conclusion about the direction, size, or precision of an efficacy comparison. The groups’ names and the existence of an endpoint definition are not evidence of an outcome. Nor does the enrollment figure establish how many participants had usable endpoint data.

The record’s overall description focuses on extension assessments at Months 36 and 48, but the listed primary endpoint timeframe is Month 0 up to Month 12. The registry record does not clarify how these time references fit together. That ambiguity should be kept separate from the more basic absence of efficacy results.

The safety information reports serious adverse event counts for participants at risk and a separate list of terms with percentages. It does not provide enough context to attribute the listed percentages to a group or to assess causality. These data cannot replace a complete safety analysis, and they do not answer the efficacy question.

General: an endpoint definition describes what a study intends to measure; a result requires observed outcome data and a stated analysis. A trial can have a randomized design and a clinically defined outcome while still lacking posted estimates needed for statistical interpretation. The registry record supports description of the study design and planned measurements, but not a claim that either vaccine group had a particular efficacy outcome.

13. Why This Trial Matters Statistically

Statistically, this study illustrates the distinction between a trial’s design and its reported evidence. The registry identifies randomization, parallel groups, an endpoint, and a defined HPV-negative and seronegative analysis population. Those details describe how the research question was framed. They do not supply the group-specific endpoint data needed to estimate a comparison.

The endpoint combines lesion classification with detection of particular HPV types in the lesion. This makes its definition more specific than a broad count of cervical abnormalities. It also means that interpretation depends on the tissue assessment, HPV detection, eligibility criteria, and follow-up period. The registry describes some of these rules but does not report endpoint counts or the number of participants meeting the analysis population definition.

The extension framing and primary endpoint timeframe do not align clearly in the record: the general description emphasizes Months 36 and 48, while the endpoint is labeled Month 0 up to Month 12. Recognizing such ambiguity is important because a result’s meaning depends on when the outcome was assessed. The record does not resolve the issue.

Finally, the study lists multiple outcome measures but no analyses. This makes it impossible to evaluate multiplicity, estimate uncertainty, or distinguish primary from secondary findings in reported results. The statistical lesson is not about a treatment effect; it is about the information needed to interpret one. Randomization can support a comparative design, but an interpretable result also requires outcome data, denominators, analysis details, and uncertainty estimates.

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 central limitation of the registry record for statistical interpretation is the absence of a reported primary-endpoint analysis. It gives no group-specific primary outcome counts, analyzed denominators, effect estimate, confidence interval, or p-value. Although enrollment is reported as 752, the record does not state how many participants contributed to the endpoint analysis.

The endpoint timeframe is unclear in relation to the extension. The study description refers to objectives and outcome measures at Months 36 and 48, while the primary endpoint is listed as running from Month 0 up to Month 12. The registry record does not explain this difference or specify which timing governs an efficacy comparison.

The endpoint population is defined by HPV DNA and serology criteria from the primary study, but the record does not give its size or explain how unavailable tests and outcomes were handled. Analysis population methods, missing-data procedures, and the approach to multiple outcomes are not reported in the registry record.

Although the study is labeled randomized, the randomization method and allocation concealment are not described. No masking is reported, and the record does not explain whether outcome assessors were masked. Statistical methods for the efficacy comparisons, including any covariate adjustment or model choice, are not reported. A trial-specific sample-size justification is also not reported in the registry record.

Safety reporting is limited in context: the serious adverse event term percentages lack stated group attribution and denominator, and event timing and causality are not described. The registry also does not report death counts. These limitations prevent a fuller assessment of safety or comparative efficacy from the record alone.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Extension Study of the Efficacy of the GSK 580299 Vaccine in Japanese Women Vaccinated in the Primary NCT00316693 Study — NCT00929526.
• Registry record last updated 2016-10-20; status last verified 2016-09.
• Results first posted 2012-10-15.
• 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

NCT00929526 is a completed Phase 3 randomized, parallel-group extension study with no masking, listed enrollment of 752, and Japanese women from primary study NCT00316693. The groups are identified by prior receipt of 3 doses of Cervarix™ or 3 doses of Aimmugen™. Extension procedures included liquid-based cytology and blood sampling, with intended assessment of cervical lesions, HPV infection, safety, and humoral immune response.

The primary endpoint is a count of histopathologically confirmed CIN1+ cases associated with HPV16 and/or HPV18 in the lesional tissue component. Its timeframe is listed as Month 0 up to Month 12, while the extension description refers to assessments at Months 36 and 48. No primary-endpoint analysis is reported in the registry record. Serious adverse event counts and selected terms are listed, but context for the term percentages is limited. Methods for missing data, multiplicity, and efficacy analysis are not reported in the registry record.