HPV Vaccine Intervention for Young Sexual Minority Men: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for HPV Vaccine Intervention for Young Sexual Minority Men (NCT04032106), a randomized na study. The primary outcome is Human Papillomavirus (HPV) Vaccine Initiation and Completion.

2. Clinical Question

The central statistical question is whether vaccination outcomes differ among participants assigned to standard information, Outsmart HPV with unidirectional reminders, or Outsmart HPV with interactive reminders. The two intervention groups share the Outsmart HPV approach but differ in whether a participant can respond to a reminder. The standard-information group provides a comparison with a mobile-friendly source of HPV and vaccine information.

The registry describes the intended outcomes as counts and proportions of participants who initiate and complete the series during the study period. These are related but distinct outcomes: initiation concerns starting vaccination, while completion concerns completing the series. The record does not provide outcome counts, proportions, estimates of between-group differences, confidence intervals, or statistical tests. It therefore does not establish from the posted results whether any group had more initiation or completion.

The brief summary describes the intervention as potentially increasing initiation and completion among unvaccinated young sexual minority individuals. That statement describes the study rationale, not a reported finding. The age limits, the exact definition of vaccination status at entry, and the detailed eligibility criteria are not reported in the registry record.

3. Trial Design

This is a randomized, parallel-group trial with single masking, and the record lists enrollment as 1227. The trial has three groups: standard HPV information, Outsmart HPV with unidirectional vaccine reminders, and Outsmart HPV with interactive vaccine reminders. The record identifies the sponsor as Ohio State University Comprehensive Cancer Center. The recorded start date is 2019-10-03, the primary completion date is 2022-03-30, and the status is completed.

Randomization means that allocation to a group is intended to be determined by chance rather than by participant or researcher choice. In general, this can help make groups comparable at the start of a study, although it does not guarantee identical group characteristics. The registry does not report the randomization procedure, allocation ratio, blocking or stratification, or concealment procedures. The record identifies masking as single but does not specify who was masked or how masking was maintained.

The parallel design means participants are assigned to a group and evaluated in that group rather than crossing through each intervention. The active comparisons can address different questions: each Outsmart HPV group can be compared with standard information, and the two reminder formats can be compared with one another. The registry does not report a prespecified primary pairwise comparison, a hierarchy among these comparisons, or a statistical analysis plan.

The phase field is listed as NA, while the brief summary calls the trial phase III. Both descriptions appear in the record; the reason for the difference is not reported. The interventions also include best practice, informational intervention, questionnaire administration, and text message-based intervention entries. The detailed procedures, timing and amount of contact, and delivery fidelity are not reported in the registry record.

The recorded enrollment is the trial-wide enrollment figure, not an outcome count. The record does not give group-specific enrollment or analysis populations for the primary endpoint. The group denominators listed for safety reporting should not be treated as a substitute for a reported endpoint analysis population.

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

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 Human Papillomavirus (HPV) Vaccine Initiation and Completion, measured over Baseline up to 9 months.

The primary endpoint is described as the number and proportion of participants who initiate and complete the HPV vaccine series during the study period. Its time frame is baseline up to 9 months, and the unit is participants. This endpoint therefore concerns participant-level vaccination milestones over a defined follow-up interval, rather than a continuous measurement or time-to-event outcome.

Initiation and completion capture different stages of vaccination. Reporting both can help distinguish whether participants start vaccination from whether they go on to complete the series. Counts communicate how many participants meet each definition, while proportions put those counts in relation to a specified group denominator. For interpretation, the denominator and the operational definition of each outcome matter; the registry record does not provide the detailed endpoint definitions, denominator rules, or handling of participants with incomplete follow-up.

As a general statistical point, binary outcomes are often compared between groups using proportions, risk differences, ratios, or regression models. The choice affects how an effect is expressed and what assumptions are used. No effect estimate or model for this endpoint is reported in the registry record, so there is no basis for describing the size or precision of a group difference.

The record names initiation and completion together in the primary outcome description but does not identify a single one as the primary measure, explain how the outcomes are jointly assessed, or state how multiple categories or follow-up measurements are handled. The registry's note indicates that the primary outcome has several categories or time points and was not reduced to one comparison. Accordingly, no single numerical comparison should be inferred from the endpoint description alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization is a method for assigning participants to groups by chance. In general, random assignment helps reduce systematic differences between groups at baseline, including differences that investigators may not have measured. It does not ensure that the groups are identical, and its benefits for causal interpretation depend on maintaining the assigned comparisons and accounting for participants and outcomes consistently. The registry identifies the trial as randomized but does not describe the random sequence method, concealment, allocation ratio, or analysis approach.

What does a parallel-group comparison mean?

In a parallel-group design, participants receive the approach assigned to their group during the trial rather than switching between approaches. Here, the groups are standard HPV information, Outsmart HPV with unidirectional reminders, and Outsmart HPV with interactive reminders. A comparison of either intervention group with standard information addresses the intervention package relative to that comparator. A comparison between the two reminder groups addresses the difference between the reminder formats within the Outsmart HPV approach. The registry does not state which of these comparisons was designated as the main comparison.

How should counts and proportions be understood?

A count is the number of participants meeting an outcome definition. A proportion relates that count to a denominator, such as the number of participants eligible for the endpoint analysis. The denominator must be clear to interpret a proportion, especially when follow-up is incomplete or eligibility differs across outcomes. The record describes counts and proportions for vaccine initiation and completion but does not report the observed values, endpoint denominators, or detailed rules for classifying participants.

In general, a binary endpoint can be analyzed using methods that compare proportions or model the probability of the event. Different methods can adjust for covariates or use different effect scales. The registry record does not identify a model, adjustment variables, or a primary effect measure. Consequently, no method-specific assumptions or adjusted results can be evaluated from the posted record.

What does masking contribute?

Masking can reduce the influence of knowledge of group assignment on behavior, outcome assessment, or other trial procedures. The record labels the trial single-masked, but it does not state which people were masked, whether participants knew which reminder format they received, or which endpoint procedures were masked. Because the interventions use different information and reminder experiences, details about masking and outcome ascertainment would be important for judging possible measurement or behavior effects; those details are not reported in the registry record.

What does the planning illustration mean?

General sample-size planning asks how many participants would be needed to detect a chosen effect with a specified statistical procedure and assumptions. The record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It describes planning for a stated fraction of the observed effect; it also specifies that non-time-to-event illustrations are expressed as participants per arm. The numeric planning outputs and the effect value used are not reported in the registry record.

Such illustrations are not observed power and do not show what the completed trial established. They depend on the effect assumed for planning and on the method's assumptions. The record does not report the trial's own sample-size justification, the effect targeted in its original design, or whether the illustration's assumptions match the design. Without the numerical outputs, no specific planning requirement can be interpreted.

Why does multiplicity matter?

When a study evaluates multiple outcomes, groups, or time points, repeated testing can make a nominally notable result more likely to occur by chance. General approaches include prespecifying a primary comparison, adjusting inference across tests, or treating some analyses as exploratory. The registry describes multiple categories or time points for the primary outcome and indicates that it was not reduced to one comparison. It does not report a multiplicity strategy, a test hierarchy, or analysis results. Therefore, the inferential treatment of the several outcome components cannot be assessed.

Finally, a statistical result requires more than a design description: it requires outcome data, a defined analysis population, methods for incomplete data, and an estimate with uncertainty. Those elements are not reported for the primary endpoint in the registry record. The design information can clarify what comparisons were intended, but it cannot replace the absent endpoint results.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome description includes both vaccine initiation and completion, and the record notes several categories or time points. It also indicates that the outcome was not reduced to one comparison. The registry does not report a prespecified hierarchy of outcomes, a primary comparison among the three groups, or a method for controlling the chance of false-positive findings across multiple comparisons. Whether multiplicity was handled in the trial's analysis is not reported in the registry record.

The registry record does not describe the analysis population for the primary endpoint. It does not say whether analyses were based on assigned group, participants who completed follow-up, or another population. No endpoint-specific denominators, exclusions, or participant flow are reported. The study's recorded enrollment cannot by itself establish how many participants were included in each endpoint analysis.

Missing-data details are also not reported. The record does not state how incomplete follow-up, missing vaccination information, or partially observed series completion were handled. In general, missingness can affect estimates when participants with missing outcomes differ from those with observed outcomes. Methods such as complete-case analysis, imputation, or sensitivity analyses rely on assumptions that should be described and assessed; none is specified in the registry record.

Because the analyses, outcome denominators, and missing-data methods are absent, the robustness of any group comparison cannot be judged from the registry record. These omissions do not establish that the investigators did not conduct such analyses; they mean that the corresponding 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.

The safety record lists three groups: standard HPV information, Outsmart HPV with unidirectional reminders, and Outsmart HPV with interactive reminders. For those groups, the serious adverse event counts are 0, 0, and 0; other adverse event counts are 0, 0, and 0; and deaths are 0, 0, and 0. The corresponding numbers at risk are 412, 407, and 408.

These figures are event counts as recorded, not estimates of comparative risk. They do not show whether event collection was complete, how events were defined, how long participants were monitored for safety, or how events were assessed for relatedness to an intervention. Those details are not reported in the registry record. The counts also do not establish that the groups have identical safety profiles.

In general, zero recorded events over a study period do not establish that an event is impossible or that the underlying event rate is exactly zero. Interpretation depends on the amount and completeness of observation, the event definition, and the population monitored. The figures should therefore be read narrowly: no serious adverse events, other adverse events, or deaths are listed for these groups in the registry record. They are not a substitute for the missing primary vaccination outcome analyses.

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

The registry record establishes that a randomized, parallel-group trial compared standard HPV information with two versions of an Outsmart HPV mobile health intervention. It specifies the intended focus on vaccine initiation and completion from baseline up to 9 months. It also records the trial as completed and gives a total enrollment of 1227. These details clarify the study question and broad design.

The record does not establish whether either intervention increased initiation or completion, whether interactive reminders differed from unidirectional reminders, or how large or precise any difference might be. Outcome counts, proportions, statistical comparisons, confidence intervals, and p-values are not reported in the registry record. The study rationale's statement that the intervention may increase vaccination is not an outcome finding.

In general, a statistically detectable difference is not automatically large or important, and a small p-value would not by itself establish practical importance. Conversely, a result that is not statistically distinguishable from no difference would not prove that groups are equivalent. Judging those questions requires estimates, uncertainty intervals, appropriate comparison methods, and a clear account of the analysis population. Those results and details are absent from the posted record.

The trial's intended population is described in terms of young individuals with same-sex partner history, attraction to males, or gay, bisexual, or queer identity. The record does not provide specific age limits or detailed eligibility criteria, so the exact population to which any eventual results might apply cannot be fully characterized from this information. The intervention descriptions likewise do not provide enough detail to assess the intensity or fidelity of delivery.

The reported safety counts are limited to the registry's recorded event figures and do not answer the vaccination endpoint question. Taken together, the record supports a description of the study's design and planned outcomes, but not a conclusion about the comparative effectiveness, precision, or safety of the interventions.

13. Why This Trial Matters Statistically

This trial poses a practical statistical comparison among three approaches to HPV information and reminders. Separating the two Outsmart HPV reminder formats makes it possible in principle to distinguish the broader intervention from a specific feature: whether reminders permit participant responses. The standard-information group also provides a comparator distinct from either reminder approach. These comparisons illustrate why a clear analysis plan matters in a multi-group study.

The endpoint combines two vaccination milestones that should not be conflated. Initiation and completion can reflect different steps, and the counts and proportions for each would be needed to describe those outcomes. A single broad statement about vaccination would not show which milestone changed or how consistently outcomes were observed. The registry's description of multiple categories or time points makes clear that defining and prioritizing comparisons is relevant.

From a statistical perspective, randomized assignment offers a framework for comparing groups, while masking, consistent outcome ascertainment, follow-up, and analysis choices affect how persuasive those comparisons are. The registry gives only limited detail on these procedures and does not report the endpoint analyses. Thus, the design is informative about the intended question, but the record does not permit evaluation of the actual estimated effects or their uncertainty.

The record also highlights the difference between planning and evidence. A planning illustration based on an assumed fraction of an observed effect is not a trial result and cannot substitute for estimates from participant outcomes. Similarly, a completed status and reported enrollment do not answer whether the intervention groups differed. Statistical interpretation requires the endpoint results, denominators, analysis population, and uncertainty measures, which are not reported in the registry record.

The study's focus on a population-specific mobile health intervention raises questions about how behavioral reminders are evaluated, but the record alone cannot establish how broadly any future findings would generalize. Eligibility detail, implementation information, outcome definitions, and complete results would be needed to assess that scope. The main statistical importance of the record is therefore its clearly differentiated three-group question, alongside the substantial limits imposed by the absence of posted outcome analyses.

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 most consequential limitation for interpretation is that the registry record does not report primary endpoint results. There are no group-specific initiation or completion counts or proportions, no estimates of differences, and no uncertainty intervals or tests. The record therefore cannot support a statistical conclusion about the intervention comparisons.

Important design and analysis details are also missing. The record does not state the allocation ratio, randomization procedure, identity of the masked parties, endpoint assessment procedures, primary comparison, or adjustment methods. It does not report endpoint denominators, participant flow, analysis populations, missing-data handling, or a multiplicity plan. Without those details, it is not possible to assess whether the observed comparisons, if reported elsewhere, would be vulnerable to selection, measurement, or analysis choices.

The outcome description does not give operational definitions for initiation and completion or explain how the several categories or time points are to be combined or prioritized. The record also does not give exact age limits, detailed eligibility criteria, or enough intervention-delivery information to characterize implementation fully. These omissions limit assessment of the target population, measurement, and potential generalizability.

The phase information is inconsistent within the record: the phase field is listed as NA, while the brief summary calls the trial phase III. The reason is not reported. The safety figures list no events, but event definitions, collection methods, monitoring duration, and completeness are not described. The completed status and recorded enrollment do not resolve these gaps or substitute for the missing results.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: HPV Vaccine Intervention for Young Sexual Minority Men — NCT04032106.
• Registry record last updated 2025-03-14; status last verified 2025-03.
• Results first posted 2023-05-06.
• 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 describes a randomized, single-masked, parallel-group trial of an HPV vaccine intervention for young sexual minority men. The three groups are standard HPV information, Outsmart HPV with unidirectional vaccine reminders, and Outsmart HPV with interactive vaccine reminders. Recorded enrollment is 1227, and the status is completed.

The primary outcome concerns the number and proportion of participants who initiate and complete the HPV vaccine series from baseline up to 9 months. The registry record does not report outcome analyses, endpoint counts or proportions, group comparisons, confidence intervals, or p-values. It also does not report the primary analysis population, missing-data methods, or multiplicity strategy.

The safety figures list zero serious adverse events, zero other adverse events, and zero deaths in each group. These counts are not accompanied by detailed safety definitions or monitoring methods. The record identifies the sponsor as Ohio State University Comprehensive Cancer Center and records dates of 2019-10-03 for study start and 2022-03-30 for primary completion. Overall, the record describes the study design and intended question but does not report results that establish comparative outcomes.