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 Increasing Vaccine Uptake Among Adolescents in the Rural South (NCT04999267), a na na study. The primary outcome is Difference in the Percentage of Adolescents Who Ever Received at Least One Dose of HPV Vaccination in the Intervention Group After the Intervention Implementation Compared With Before Intervention Implementation.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04999267 |
| Phase | NA |
| Condition | Vaccine Hesitancy |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 2 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Duke University |
| Results posted | Yes |
2. Clinical Question
Population
Middle schoolers in rural North and South Carolina are the population described for the study. The primary outcome uses vaccination records for adolescents by district. The registry record reports enrollment of 2, but does not clarify how that count relates to the adolescent population or to the districts contributing vaccination records.
Intervention
INVEST is described as a tailored, school-based intervention intended to increase vaccine uptake among adolescents. The intervention is associated with intervention school districts. Specific activities or components are not reported in the registry record.
Comparator
The primary outcome compares the intervention group after implementation with the same intervention group before implementation. The registry record identifies a single-group model and does not describe a concurrent control group. This is a before-and-after contrast, not a randomized comparison between like-for-like groups.
Primary question
Did the percentage of adolescents in the intervention group who had ever received at least one dose of HPV vaccine differ after implementation compared with before implementation? The outcome is defined at baseline and 9 months. Although the registry identifies this as the primary question, it does not report the numerical percentages, their difference, or an uncertainty estimate.
3. Trial Design
The registry describes INVEST as a completed, single-group study of a tailored school-based intervention intended to increase vaccine uptake among adolescents in rural North and South Carolina. Duke University is listed as the sponsor. The study is categorized as phase NA, with allocation listed as NA and masking listed as none. These entries do not describe a randomized, masked comparison.
The primary outcome is framed as a comparison within the intervention group: vaccination status after implementation versus before implementation. The registry names baseline and 9 months as the timeframe. It describes the underlying information as official vaccination records for middle schoolers by district, collected before and after implementation. It does not clarify whether the before-and-after records represent the same individual adolescents, different sets of adolescents, or district-level aggregates.
The registry reports enrollment of 2. It does not explain the unit represented by this enrollment figure or how it relates to the adolescent records used for the primary outcome. The intervention is associated with intervention school districts, but the number of schools or districts is not reported in the registry record.
The study start date is 2021-08-31, and the primary completion date is 2022-11-03. The status is completed. The registry also lists two secondary outcomes: change in the percentage completing the HPV vaccination series and intervention fidelity across intervention schools. Details of intervention delivery, the assessment schedule for those secondary outcomes, and the analysis plan are not reported in the registry record. The design therefore supports describing a planned before-and-after assessment, but not attributing a numerical change or a causal effect to the intervention.
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: School nurses from intervention schools were not considered enrolled.
Overall Study
| Stage | INVEST Intervention School Districts |
|---|---|
| STARTED | 2868 |
| COMPLETED | 2868 |
| NOT COMPLETED | 0 |
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: The participants are school districts; baseline characteristics data were not collected.
| Characteristic | Unit | INVEST Intervention |
|---|---|---|
| Participants analysed | 0 | |
| Sex: Female, Male: Female | — | |
| Sex: Female, Male: Male | — |
6. Primary Endpoint
The registry lists the primary outcome as Difference in the Percentage of Adolescents Who Ever Received at Least One Dose of HPV Vaccination in the Intervention Group After the Intervention Implementation Compared With Before Intervention Implementation, measured over Baseline, 9 months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of adolescents |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the difference in the percentage of adolescents in the intervention group who had ever received at least one dose of HPV vaccine after implementation compared with before implementation. Vaccination status is defined as at least one dose versus no doses. The registry says that official vaccination records for middle schoolers, organized by district, are used to establish status at baseline and 9 months.
A percentage expresses how common an outcome is within a defined group. A before-and-after difference can describe whether the recorded share with at least one dose changed over the assessment periods. It does not, by itself, establish that the intervention caused any change: other changes over time, differences in the adolescents represented in each period, and the way records are aggregated could also matter. These are general considerations for interpreting before-and-after percentages.
Using recorded vaccination status makes the endpoint directly tied to the outcome the intervention seeks to influence. However, the registry record does not report the actual percentages, the estimated difference, or its uncertainty. It also does not report how missing or incomplete vaccination records are handled, or whether the comparison uses individual-level or district-level analysis. The endpoint is therefore defined, but its observed magnitude and precision cannot be assessed from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the question the study set out to address, but it does not provide the numerical primary outcome results. It names the outcome as a difference in the percentage of adolescents who had ever received at least one HPV vaccine dose after versus before implementation. No before-and-after percentages, estimated difference, confidence interval, or p-value are reported in the registry record. Consequently, the direction, size, and statistical precision of any observed change cannot be described.
The design is single-group and uses a before-and-after contrast. Such a contrast can document a change between two measurement periods in the group being studied, but it has no concurrent control group in the registry description. General statistical interpretation therefore distinguishes an observed temporal change from an effect attributable to an intervention. Without a control group, the comparison alone cannot separate the intervention's contribution from other explanations, such as changes in the population represented by records or other changes occurring during the study period. The registry does not report whether the same adolescents contributed records in both periods.
The primary outcome is based on official vaccination records, described as middle schoolers' status by district. This establishes the broad source and level of organization of the outcome data, but not the analysis unit. The registry does not say whether the reported percentage was calculated across individuals, districts, or another grouping, nor how variation across districts was addressed. Those details affect how precisely a pooled before-and-after difference can be interpreted.
The two secondary outcomes concern completion of the HPV vaccination series and fidelity across intervention schools. The registry identifies these outcomes but does not report their numerical findings. It also does not report the components of the intervention, the degree of implementation, or whether outcome data were complete. Those omissions limit interpretation of both uptake and how the intervention was delivered.
The record lists zero for the reported serious-event and other-event counts, with zero at risk in the intervention group. These entries do not establish that no events occurred among all study participants: the listed at-risk count is zero, and the registry does not explain the scope or completeness of adverse-event collection. The safest interpretation is limited to what the record lists, rather than treating these counts as a general safety finding.
Overall, the registry supports describing the study's objective, design, endpoint definition, and planned assessment periods. It does not support a conclusion about the observed change in HPV vaccination, the reliability of that change, or whether it can be attributed to INVEST.
9. Statistical Methods Explained
The primary endpoint is a percentage measured before and after implementation. The registry defines the outcome as whether an adolescent had received at least one HPV vaccine dose. In general, a percentage is a proportion expressed on a percent scale. Comparing two such measurements can describe a change over time, but the registry record does not report the actual values or the statistical method used to compare them.
A confidence interval, in general, describes a range of values compatible with the data under a specified statistical model and procedure. Its width conveys precision: a narrower interval indicates more precise estimation under those assumptions, while a wider interval indicates less precision. No confidence interval for the primary endpoint is reported in the registry record, so the precision of any estimated change cannot be assessed. A p-value, in general, describes how unusual data at least as inconsistent with a specified null hypothesis would be under that hypothesis and the chosen model. It does not measure the size or practical importance of a change. No primary-outcome p-value or hypothesis-testing procedure is reported.
The comparison is described as after implementation versus before implementation in the intervention group. The record does not specify whether the observations are paired at the individual level. Pairing would mean that the same unit is measured in both periods; repeated measurements on the same individuals can have a different uncertainty structure from comparing separate groups at different times. The outcome description instead says records are obtained for middle schoolers by district, without clarifying whether the same adolescents contribute at both times. It would therefore be inappropriate to assume a paired analysis or an independent-groups analysis.
The record also does not specify the statistical unit used for inference. Records are organized by district, while the endpoint is expressed as a percentage of adolescents. If observations are grouped within schools or districts, outcomes within a group may be more alike than outcomes across groups. In general, this clustering can make a calculation that treats every observation as independent overstate precision. The registry does not report whether clustering was accounted for, how many schools or districts contributed data, or whether the analysis used individual records or aggregated percentages.
The primary outcome is binary at the adolescent level: at least one dose or no doses. General methods for binary outcomes can estimate a proportion or compare proportions, but the registry record does not identify a model, test, variance estimator, or adjustment strategy. The endpoint is also described as a difference in percentages; no definition is given for the exact calculation of that difference or for any adjustment for other characteristics. No adjusted estimate should be inferred from the outcome description alone.
Interpretation also depends on the source and completeness of outcome data. Official vaccination records are the stated source, but the registry does not describe record linkage, validation, missing-record handling, or how adolescents with unknown status are classified. In general, incomplete outcome ascertainment can affect both the estimated percentage and its uncertainty. The direction and magnitude of any such effect depend on which records are missing and why; those details are not reported.
The registry lists a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It describes the target effect as a stated fraction of the observed effect. These are planning assumptions, not a description of the actual single-group study design: the registry does not list a two-arm randomized comparison. The resulting sample-size values are not reported in the registry record. Such planning illustrations are not observed power and should not be read as evidence that the study had a particular chance of detecting an effect.
The registry does not report interim analyses, stopping rules, a formal statistical analysis plan, or the method for handling multiple outcomes. It lists three outcome measures and two analyses, but those counts do not identify which outcomes were analyzed together or how inference was controlled. Without an analysis description or numerical estimates, the appropriate statistical reading is that the endpoint and broad comparison are defined, while the calculation and uncertainty of the result remain unreported.
These explanations of percentages, confidence intervals, p-values, pairing, and clustering are general statistical concepts. They describe issues relevant to this design, not procedures confirmed to have been used in INVEST.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary outcome and two secondary outcomes. The primary outcome concerns adolescents who ever received at least one HPV vaccine dose. The secondary outcomes concern completion of the HPV vaccination series and fidelity across intervention schools. The record also lists three outcome measures and two analyses. It does not report how those measures map to the analyses, whether additional analyses were performed, or which outcomes were included in each analysis.
When several outcomes or statistical tests are examined, the chance of at least one apparently unusual result can increase. General approaches to multiplicity include specifying a primary outcome in advance, adjusting inference across a defined family of tests, or treating secondary findings as exploratory. The registry identifies a primary outcome, but does not report whether any multiplicity adjustment was planned or used. No test results are reported, so the effect of any adjustment cannot be assessed.
Missing-data methods are not reported in the registry record. In particular, it does not describe missing vaccination records, incomplete follow-up, exclusions, or how unknown vaccination status was handled. It also does not define analysis populations, such as which adolescents or districts were included in each endpoint analysis. The enrollment figure is 2, but the record does not explain its unit or its relationship to the outcome records. These omissions prevent assessment of the analyzed population and the potential influence of incomplete data.
The absence of these details in the registry record should not be taken as proof that no procedures existed; it means the record does not report them. Without outcome estimates, analysis-population definitions, and missing-data and multiplicity methods, readers cannot assess the robustness of the reported findings.
11. What the Result Does, and Does Not, Mean
The registry record describes a study designed to assess the feasibility and preliminary efficacy of a school-based intervention for increasing vaccine uptake among adolescents in rural North and South Carolina. It defines a primary before-and-after outcome based on the percentage of adolescents with at least one HPV vaccine dose, using official vaccination records at baseline and 9 months. These details establish the intended question and measurement approach.
The record does not report the numerical primary outcome findings. It therefore does not show whether the percentage rose, fell, or remained similar, nor how large or precise a change may have been. The secondary outcomes are named, but their numerical results are also not reported. No conclusion about the observed uptake or series completion can be drawn from the outcome definitions alone.
Even if a before-and-after change were reported, a single-group comparison would describe change over time rather than isolate the intervention's causal effect. Without a concurrent control group in the registry description, the comparison cannot distinguish the intervention's influence from other factors that may have changed over the same period. The record also does not clarify whether the same adolescents were measured in both periods or how district-level data were analyzed.
The study's completed status indicates that the registry marks the study as completed; it does not provide the missing outcome estimates. Similarly, the listed event counts, paired with zero at risk, do not establish that no adverse events occurred across the population relevant to the study. The scope of event collection is not reported.
In practical statistical terms, the record permits a careful description of the research question and its limitations, but not an estimate of the intervention-associated change or a judgment about its precision. Any claim about the magnitude, direction, statistical significance, or causal meaning of a result would go beyond what the registry record reports.
12. Why This Trial Matters Statistically
This study is statistically notable because it frames vaccine uptake as a measurable before-and-after change in a defined setting: intervention school districts in rural North and South Carolina. The primary endpoint uses the share of adolescents recorded as having ever received at least one HPV vaccine dose. Linking an outcome to official vaccination records gives the question a concrete measurement basis, while organizing the records by district raises important questions about the level of analysis and the dependence of observations within groups.
The design also illustrates a distinction central to clinical and public-health research: a change observed over time is not automatically an intervention effect. A single-group before-and-after comparison can describe what happened between assessment periods, but without a concurrent comparison group it cannot, on its own, separate an intervention contribution from other time-related explanations. This distinction matters when interpreting school-based programs, where the setting and the population represented by records may change across periods.
The record names both uptake and implementation fidelity as outcomes. In general, measuring implementation alongside an outcome can help distinguish questions about whether an intervention was delivered from questions about whether uptake changed. However, no numerical findings or implementation details are reported in the registry record, so that distinction cannot be evaluated for INVEST.
Finally, the record demonstrates why transparent reporting of estimates, uncertainty, analysis populations, and missing-data methods is necessary. Without those details, readers can understand the intended endpoint and design but cannot judge the magnitude or precision of the observed change. The study's rural focus and its stated aim of addressing under-vaccination provide context for the question, not evidence of an outcome.
13. 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 for statistical interpretation is that numerical results for the primary endpoint are not reported in the registry record. The before-and-after percentages, their difference, and an uncertainty estimate are absent. Consequently, the direction and magnitude of any change cannot be evaluated. Results for the two secondary outcomes are also not reported.
The single-group design lacks a concurrent control comparison in the registry description. A before-and-after contrast can be affected by changes over time that are not caused by the intervention. The registry does not report how the study addressed this limitation, and no causal attribution is supported by the design description alone.
The relationship between enrollment of 2 and the outcome data is unclear. The primary outcome uses vaccination records for middle schoolers by district, but the record does not explain the enrollment unit, the number of districts or schools, or the number of adolescents represented. It also does not say whether the same adolescents contributed records before and after implementation. These ambiguities limit assessment of the analysis unit, dependence among observations, and precision.
Additional details needed to evaluate the endpoint are not reported in the registry record. These include how missing or unknown vaccination records were handled, the statistical model or test, any adjustment for district or participant characteristics, the analysis populations, and the approach to multiplicity. Intervention components and fidelity results are also not described in enough detail to connect implementation with uptake findings.
The adverse-event listing reports zero at risk as well as zero event counts. Without further information about the population monitored and completeness of collection, these entries do not establish the absence of events. Together, the lack of numerical outcomes and the limited design and analysis detail sharply constrain conclusions that can be drawn from the registry record.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Increasing Vaccine Uptake Among Adolescents in the Rural South — NCT04999267.
- Registry record last updated 2025-12-10; status last verified 2025-11.
- Results first posted 2024-12-04.
- 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.
17. Record Summary
INVEST is a completed, single-group study sponsored by Duke University. It evaluates a tailored school-based intervention intended to increase adolescent vaccine uptake in rural North and South Carolina. The registry lists enrollment of 2, phase NA, allocation NA, and masking none. It gives a study start date of 2021-08-31 and a primary completion date of 2022-11-03.
The primary outcome is the before-and-after difference in the percentage of adolescents with at least one HPV vaccine dose, assessed at baseline and 9 months using official vaccination records by district. Secondary outcomes address HPV vaccination-series completion and intervention fidelity across schools. The registry record does not report numerical outcome results, uncertainty estimates, missing-data methods, or a detailed analysis plan. Its design and endpoint can be described, but the magnitude and interpretation of any observed change cannot be established from the record.