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 Gardasil in Mid-Adult Males (MAM) (NCT01432574), a na phase 2 study. The primary outcome is Percentage of Participants Seropositive at Month 7.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01432574 |
| Phase | Phase 2 |
| Condition | Human Papillomavirus |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 150 |
| Arms in the primary outcome | n/a |
| Lead sponsor | H. Lee Moffitt Cancer Center and Research Institute |
| Results posted | Yes |
2. Clinical Question
Population
Men ages 27-45 who had completed 4 years of observation in the Human Papillomavirus infection in men (HIM) Study. For the primary endpoint, the stated population is participants with specimens contributing to both Day 1 and Month 7 serum HPV antibody evaluations. The record does not give the number of participants in that endpoint population.
Intervention
Gardasil, administered as 3 injections at 3 separate visits. The record describes this as the study vaccine and identifies the study as Phase II. It does not report the specific timing of each injection in the brief arm description.
Comparator
There is no comparator group in the registry design information. The study is described as single group, with allocation recorded as NA and masking as none. Consequently, the record does not establish a randomized or masked comparison against another intervention or a control condition.
Primary question
The primary endpoint is titled “Percentage of Participants Seropositive at Month 7.” Its description focuses on participants who were seronegative at Day 1 and says they were to be categorized as seroconverted based on increased titers for each vaccine component at Month 7. The registry record does not report the resulting percentage, the number meeting the endpoint, or an analysis estimate.
In statistical terms, this is a question about an antibody response measured after vaccination, not a registry-reported comparison of outcomes between randomized groups. The antibody assessment concerns HPV types 6, 11, 16, and 18, measured with a multiplex competitive Luminex immunoassay. The endpoint description identifies an assay and an assessment time, but does not provide the observed titers or a result for the stated seropositivity or seroconversion outcome. The registry record also does not report how the primary endpoint was analyzed. It therefore supports describing the intended measurement and study population, but not quantifying the observed immune response or drawing a comparative conclusion.
3. Trial Design
This is a completed Phase II, single-group study of Gardasil in mid-adult males. The registry lists enrollment of 150 participants and describes the target population as men ages 27-45 who had completed 4 years of observation in the HIM Study. The study sponsor is H. Lee Moffitt Cancer Center and Research Institute. The registry lists Human Papillomavirus as the condition and Gardasil as the biological intervention.
The design information records allocation as NA, masking as none, and the model as single group. This means the registry does not describe randomized allocation, a blinded assessment, or a like-for-like control arm. The study arm is called Gardasil Vaccine. Its description says participants received a total of 3 injections at 3 separate visits. The timing between those visits is not reported in the registry record.
The registry labels the study completed and lists a start date of 2013-02-19 and a primary completion date of 2014-05-23. These entries describe the study record, but do not supply results for the primary endpoint. The listed secondary outcome is change in antibody titers. The registry reports 2 outcome measures and 0 analyses; the analysis methods and results are not reported in the registry record.
A single-group design can describe outcomes observed among participants who received an intervention, but it does not by itself establish what would have happened to comparable participants under another condition. Without a comparator, outcome changes cannot be separated from other influences through a between-group contrast. The absence of masking is also relevant when outcomes involve judgment or reporting; the primary endpoint is based on a laboratory antibody assay, but the registry does not explain how laboratory personnel or endpoint processing were handled. Further details about conduct, eligibility, follow-up, protocol deviations, and the statistical plan 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
| Stage | Gardasil Vaccine |
|---|---|
| STARTED | 150 |
| COMPLETED | 147 |
| NOT COMPLETED | 3 |
Reasons for not completing this period:
| Reason | Gardasil Vaccine |
|---|---|
| Moved | 2 |
| Not interested | 1 |
Analysis population for the primary outcome, as defined in the registry: Participants who had specimens contributing to both Day 1 and Month 7 serum HPV antibody evaluations.
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: All participants
| Characteristic | Unit | Gardasil Vaccine |
|---|---|---|
| Participants analysed | 150 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 150 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age, Continuous | years | 36 (27 to 45) |
| Sex: Female, Male: Female | Participants | 0 |
| Sex: Female, Male: Male | Participants | 150 |
| Race/Ethnicity, Customized: White | participants | 68 |
| Race/Ethnicity, Customized: Black/African American | participants | 12 |
| Race/Ethnicity, Customized: Asian/Pacific Islander | participants | 3 |
| Race/Ethnicity, Customized: Native American/Alaskan | participants | 1 |
| Race/Ethnicity, Customized: More than one race | participants | 65 |
| Race/Ethnicity, Customized: Unknown | participants | 1 |
| Region of Enrollment: United States | participants | 75 |
| Region of Enrollment: Mexico | participants | 75 |
6. Primary Endpoint
The registry lists the primary outcome as Percentage of Participants Seropositive at Month 7, measured over 7 Months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is titled “Percentage of Participants Seropositive at Month 7.” The description says serum antibodies to HPV types 6, 11, 16, and 18 were assessed using a multiplex competitive Luminex immunoassay. It describes quantifying neutralizing antibodies in serum and identifies participants with no detectable HPV antibody titers at Day 1 as the population to be categorized as seroconverted due to an increase in titer levels for each vaccine component at Month 7.
Seropositivity and seroconversion are related but not interchangeable labels. Seropositivity describes antibody status at an assessment; seroconversion generally describes a change in status or antibody response relative to an earlier assessment. The registry’s title emphasizes the percentage seropositive, while its description emphasizes initially seronegative participants and seroconversion. The record does not specify a numerical threshold for a qualifying titer increase or clarify the exact numerator implied by the title.
The stated endpoint population includes participants with specimens contributing to both Day 1 and Month 7 evaluations. The record does not give its size or the endpoint result. Antibody measurements are used as a laboratory marker of immune response. They are not, by themselves, a registry-reported measure of clinical HPV infection or disease. Those outcomes are not identified as the primary endpoint in this record, and no clinical-effect conclusion follows from the endpoint description alone.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes the study question and measurement but does not report the primary endpoint result. In particular, it gives no count or percentage of participants who were seropositive at Month 7, no result for seroconversion among those seronegative at Day 1, and no estimate of change in antibody titers. It also lists 0 analyses. There is therefore no posted statistical estimate to interpret for the primary endpoint, and no reported confidence interval or p-value with which to assess its precision or compatibility with different values.
The title and descriptive text use related but distinct endpoint language. The title names the percentage seropositive at Month 7; the description specifies that the Day 1 seronegative study population was to be categorized as seroconverted based on an increase in titer levels for each vaccine component. Both statements concern antibody response, but the record does not clarify the precise endpoint rule or report the corresponding outcome. The endpoint population is defined as participants with specimens contributing to both Day 1 and Month 7 evaluations, but the number meeting that condition is not reported in the registry record.
The enrollment of 150 is the study enrollment figure, not a reported denominator for the endpoint. It should not be substituted for the endpoint population size when interpreting a percentage. Participants without specimens at either assessment may not contribute to the stated population; the record does not report how many had complete specimens, why any specimens were unavailable, or how missing assessments were handled.
General statistical interpretation: an estimate describes the observed data, while a confidence interval expresses uncertainty around an estimate under the assumptions of the analysis. Without an endpoint estimate, denominator, or interval, neither the magnitude nor the precision of the antibody response can be evaluated from the registry record. A single-group study also lacks a concurrent comparator in the recorded design. Thus, even a reported within-group antibody response would not by itself quantify a difference attributable to vaccination relative to another condition.
The adverse-event entries are separate from the antibody endpoint. The registry lists 0 participants affected by serious adverse events and 38 affected by other adverse events in the Gardasil Vaccine group, with 150 at risk in each category. The death entry is null, so deaths are not reported in the registry record. These safety counts do not provide the missing antibody outcome, and the record does not identify whether the listed other adverse events were considered related to the intervention.
A sample-size planning illustration is not a substitute for an observed result. Its stated assumptions include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect described as a stated fraction of the observed effect. Those assumptions do not match the recorded single-group design, and the planning outputs are not reported in the registry record. They cannot establish observed power or resolve the absence of an endpoint analysis.
9. Statistical Methods Explained
General statistical background: interpreting a clinical trial result requires knowing what outcome was measured, who contributed data, how the outcome was summarized, and how uncertainty was quantified. The registry record identifies an antibody outcome and an assessment time, but does not report the endpoint estimate or analysis. The explanations below describe the statistical ideas relevant to such a result; they do not imply that a particular method was used in this study.
What does a percentage endpoint represent?
A percentage endpoint summarizes the share of a defined population meeting a stated outcome rule. It depends on both the numerator, the participants meeting that rule, and the denominator, the participants eligible for that endpoint analysis. In this record, the primary endpoint title refers to the percentage seropositive at Month 7. The endpoint description identifies participants with specimens contributing to both Day 1 and Month 7 evaluations, and further describes initially seronegative participants as being categorized as seroconverted. The record does not give the number of participants in that analysis population, the number meeting the outcome, or a final percentage.
Those population details matter because enrollment and endpoint-analysis membership need not be identical. A participant may be enrolled but lack a usable specimen at an assessment. General statistical practice would define how such cases are handled and make the denominator explicit. The registry record does not report specimen availability counts, exclusions from the endpoint population, or a missing-data rule. Accordingly, the enrollment figure of 150 cannot be treated as the denominator for the primary endpoint without additional information.
How should antibody outcomes be understood?
The registry describes an assay that simultaneously quantifies neutralizing antibodies to HPV 6, 11, 16, and 18 in serum. Antibody titers are quantitative laboratory measurements. A seropositive or seroconversion endpoint turns measurements into a categorical outcome according to a defined rule. General statistical interpretation depends on that rule: the threshold for detectable antibody, the definition of an increase, and whether success is assessed separately for each vaccine component or as a combined outcome can affect what a percentage means.
The record names the assay and says the Day 1 seronegative population was to be categorized as seroconverted based on increased titers for each vaccine component at Month 7. It does not state the threshold for a meaningful increase, clarify the relation between the title’s seropositive endpoint and the description’s seroconversion criterion, or report component-specific results. No component-level estimates or uncertainty measures are reported in the registry record. The listed secondary outcome, change in antibody titers, likewise has no posted analysis result.
What do estimates and confidence intervals usually tell a reader?
General explanation: an estimate is a numerical summary of the observed outcome under a specified analysis. For a percentage, it would summarize the observed fraction of the endpoint population meeting the rule. A confidence interval gives a range of values that are reasonably compatible with the data under the statistical model and its assumptions. Its width is informative about precision; it is not a guarantee that the true value lies within the particular interval, nor does it correct problems with outcome definition, selection, or missing data.
The registry record contains no primary estimate and no confidence interval. Thus the observed magnitude and its precision cannot be assessed. A p-value, if one had been reported, would address compatibility with a particular statistical null model, not the clinical importance of an antibody measurement. No p-value or inferential test is listed. There is no basis in the record for describing statistical significance or for making a claim about the certainty of a treatment contrast.
Why does the single-group design matter?
General explanation: a randomized comparison can use differences between groups to estimate a contrast under the trial’s design and analysis assumptions. A single-group study instead describes outcomes in one group. It can characterize observed measurements after an intervention, but does not directly reveal the counterfactual outcome that the same participants would have had under another intervention or no intervention. This study is recorded as single group, with allocation NA and masking none; a control group is not described.
Consequently, the statistical question supported by this design is descriptive unless additional comparison data and methods are available. A within-group change from Day 1 to Month 7, even if reported, would not by itself separate an intervention-associated change from other explanations. The registry record does not give an analysis plan, adjustment strategy, or a comparative estimate. It also does not report whether any interim analyses or formal hypothesis tests were planned.
How should sample-size planning be read?
General explanation: a sample-size calculation illustrates how much information a proposed design might require under assumptions about the effect to detect, variability, allocation, and error rates. It is a planning calculation, not evidence that an effect was observed and not an estimate of the probability that a result is correct. “Observed power” calculated after seeing a result is not a substitute for the estimate and its uncertainty.
The record’s planning-illustration assumptions refer to a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They describe detecting a stated fraction of an observed effect. The recorded study design is single group, not a two-arm comparison. No numerical planning outputs are reported in the registry record, and the record does not say that these assumptions were the trial’s own design assumptions. They should therefore be read only as an illustration, not as a description of the trial’s enrollment rationale or observed power. The sample-size justification for the trial itself is not reported in the registry record.
What remains unknown about the analysis?
The record lists 0 analyses. It does not identify an estimator, statistical test, confidence-interval method, covariate adjustment, or treatment of repeated or component-specific antibody measurements. It does not specify an analysis population beyond the primary endpoint’s specimen-based description. It also does not describe handling of incomplete observations, protocol deviations, or multiplicity across outcomes. These omissions mean the statistical analysis cannot be reconstructed from the registry information. General methodological explanations help clarify what such choices would mean, but cannot supply the missing decisions or results.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 2 outcome measures: the primary Month 7 seropositivity endpoint and the secondary outcome of change in antibody titers. It lists 0 analyses. The record does not report a multiplicity strategy, such as whether testing across outcomes or across HPV types was adjusted, whether one outcome was designated as the sole basis for a formal claim, or how any repeated measurements were handled. It is not appropriate to assume that a particular correction or testing hierarchy was used.
Missing-data reporting is also limited. The primary endpoint population is described as participants with specimens contributing to both Day 1 and Month 7 antibody evaluations, but its size is not reported in the registry record. The number of enrolled participants without one or both specimens, reasons for missing specimens, and methods for handling missing values are not reported in the registry record. The record does not state whether participants with incomplete observations were excluded, imputed, or handled through another approach.
The broader analysis population is not defined beyond the endpoint’s specimen-based description. The registry does not report how participants who discontinued, deviated from the injection schedule, or otherwise lacked evaluable data were treated. Such details can affect both the denominator and interpretation of an outcome, but their absence does not establish that any particular issue occurred. Without an analysis plan or posted analyses, readers cannot assess how multiplicity, missingness, or population selection influenced a numerical result. No numerical endpoint result is reported in any case.
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 |
|---|---|---|---|
| Gardasil Vaccine | 0 | 150 | 0.0% |
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 |
|---|---|
| Gardasil Vaccine | 38 of 150 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Gardasil Vaccine |
|---|---|---|
| Injection site reaction | General disorders | 19 of 150 |
| Headache | Nervous system disorders | 14 of 150 |
| Pain in extremity | Musculoskeletal and connective tissue disorders | 11 of 150 |
The registry lists 150 participants at risk for serious adverse events in the Gardasil Vaccine group and 0 participants affected. It lists 150 at risk for other adverse events and 38 participants affected. These are participant counts as recorded; they should not be read as a complete description of event type, duration, severity within the “other” category, or causal attribution. The registry does not report whether the other adverse events were considered related to Gardasil.
The deaths entry is null. A null entry is not the same as a reported count of zero; deaths are not reported in the registry record. The list of top serious-event terms is empty, but that entry does not add detail about the nature of serious events beyond the group count. The record also does not supply event-level descriptions, confidence intervals, or a comparison group for safety outcomes.
General statistical explanation: safety counts depend on the definition of an event and the period and method of surveillance. A count of affected participants is not necessarily the same as a count of individual events, because one participant may experience more than one event. Since the registry does not give event-level detail, the figures should be interpreted only at the level reported: participants affected in each listed category, alongside the stated numbers at risk. They do not support a comparative safety estimate.
12. What the Result Does, and Does Not, Mean
The record establishes that a completed Phase II, single-group study evaluated Gardasil in mid-adult males ages 27-45 who had completed 4 years of observation in the HIM Study. It describes 3 injections at 3 separate visits and an antibody assessment at Month 7, with Day 1 serum measurements also relevant to the primary endpoint population. It identifies the assay and the HPV types assessed. These details define the study context and intended immune-response measurement.
The record does not report the primary endpoint result, the antibody titer change result, or a statistical analysis. It therefore does not establish the observed proportion seropositive or seroconverted, the size of any antibody change, or the precision of either outcome. It also does not provide evidence from a randomized comparison, because the design is listed as single group, allocation NA, and masking none. The registry information cannot quantify how outcomes would differ under another condition.
The endpoint is an antibody measure. General interpretation: a laboratory immune-response marker is not automatically equivalent to a clinical endpoint such as infection or disease. The registry’s primary endpoint description does not report infection or disease outcomes, and no conclusion about those outcomes can be drawn from the antibody measurement description alone. The registry record also does not clarify the endpoint’s exact threshold or fully reconcile its seropositivity title with its seroconversion description.
The safety record reports 0 participants affected by serious adverse events and 38 affected by other adverse events among 150 at risk in each category. The death entry is null, so deaths are not reported in the registry record. These entries are descriptive and lack a comparison group and event-level detail. They do not establish comparative risk or causation. Overall, the registry supports a description of the planned measurement, study design, and listed safety counts, but not a quantitative efficacy conclusion or a comparative benefit-risk estimate.
13. Why This Trial Matters Statistically
This trial is statistically informative as an example of the difference between a clearly named endpoint and a fully reported result. The registry names an antibody endpoint at Month 7, identifies an assay and the relevant HPV types, and defines an endpoint population by specimen availability at Day 1 and Month 7. Yet the endpoint estimate, its denominator, and its uncertainty are not reported in the registry record. A defined measurement is not itself an outcome finding.
The study also illustrates why design information matters when interpreting a result. The record identifies a single-group model, no masking, and allocation NA. This design can describe observations within the enrolled group, but it does not provide the concurrent contrast available from a comparator arm. Readers need to distinguish a measured antibody response from a causal comparison, especially when no analysis result is posted.
Another statistical issue is the boundary between seropositivity and seroconversion. The endpoint title describes a Month 7 status, while the endpoint description refers to initially seronegative participants and an increase in titers. Those formulations may focus on related aspects of antibody response, but the record does not state the exact operational rule or give results by component. Precise endpoint definitions are necessary for interpreting a percentage and for comparing results across studies.
Finally, the record shows why enrollment, analysis population, and safety counts should not be conflated. Enrollment is 150; the primary endpoint population is defined by paired specimens but its size is not reported. Safety entries separately list 150 at risk and counts of affected participants. Keeping these denominators and outcomes distinct prevents unsupported recalculation or overinterpretation. The central statistical lesson is that design, endpoint definition, analysis population, and uncertainty all shape what a trial record can support.
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.
Several limitations are specific to the available registry information. The primary endpoint is not accompanied by an observed percentage, numerator, endpoint denominator, confidence interval, or p-value. The record therefore does not permit evaluation of either the magnitude or precision of the antibody result. Although enrollment is listed as 150, the endpoint population is defined by contributing specimens at Day 1 and Month 7, and its size is not reported in the registry record.
The endpoint wording is not fully resolved: the title refers to being seropositive at Month 7, whereas the description focuses on Day 1 seronegative participants categorized as seroconverted after an increase in titers. The record does not report a qualifying titer threshold, the exact success rule, or results for individual HPV types. It also does not report the secondary antibody-titer change result.
The single-group design has no registry-described comparator, and masking is recorded as none. There is no reported analysis to establish a comparative estimate. The registry does not state how missing specimens, incomplete follow-up, protocol deviations, or exclusions were handled. Details about eligibility criteria beyond the described population, injection timing, endpoint adjudication, and laboratory masking are not reported in the registry record.
The record lists 0 analyses and does not report a statistical plan, sample-size justification for the trial, multiplicity strategy, interim analyses, or adjustment methods. The planning-illustration assumptions describe equal allocation between two arms, unlike the recorded single-group design, and no numerical planning outputs are included. For safety, the record provides participant counts but not event-level descriptions or attribution; deaths are not reported in the registry record. These limits restrict interpretation to the design description and the counts actually recorded.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of Gardasil in Mid-Adult Males (MAM) — NCT01432574.
- Registry record last updated 2021-09-16; status last verified 2021-09.
- Results first posted 2015-06-01.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
This is a completed Phase II, single-group study of Gardasil in men ages 27-45 who had completed 4 years of observation in the HIM Study. Enrollment was 150. The arm description specifies 3 injections at 3 separate visits; allocation is NA and masking is none.
The primary endpoint is titled percentage seropositive at Month 7 and concerns serum antibodies to HPV types 6, 11, 16, and 18. The endpoint description identifies participants with specimens at both Day 1 and Month 7 and refers to seroconversion among those seronegative at Day 1. The primary result, the endpoint-population size, and analyses are not reported in the registry record.
The registry lists change in antibody titers as a secondary outcome, 2 outcome measures, and 0 analyses. In the Gardasil Vaccine group, 0 participants were affected by serious adverse events and 38 by other adverse events, with 150 at risk in each category. Deaths are not reported in the registry record. No randomized comparison or comparative statistical result is available in the record.