Effectiveness of Monovalent Rotavirus Vaccine (RV1): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effectiveness of Monovalent Rotavirus Vaccine (RV1) (NCT01871038), a registered phase not stated study. The primary outcome is Matched VE Participants in the Minimum Age Model.

2. Clinical Question

The study sought to assess effectiveness using children presenting for medical care rather than assigning vaccination. Active surveillance was described at Cincinnati Children's Hospital Medical Center in Cincinnati, Ohio, and the Medical University of South Carolina in Charleston, South Carolina. The enrollment narrative describes children presenting to Cincinnati Children's Hospital Medical Center as inpatients or for a short-stay or Emergency Department visit. The specific enrollment procedures at the other site are not reported in the registry record.

To classify the outcome, the study collected stool specimens and tested them for rotavirus antigen. Positive specimens were to be typed for common G and P serotypes. The clinical question is therefore about the association between prior RV1 doses and laboratory-confirmed rotavirus among children in the surveillance population. It is not a randomized comparison, and the negative controls are defined by their test result rather than by a stated vaccination status.

3. Trial Design

This was an observational case-control study based on active surveillance, not a randomized trial. The registry record reports enrollment of 362 participants and a completed status. The study start is recorded as 2009-07 and primary completion as 2012-06. Children with rotavirus-positive stool specimens formed the case group; children with rotavirus-negative specimens formed the control group. The registry record describes those groups according to test status, rather than assigning participants to vaccine or placebo.

The surveillance description names Cincinnati Children's Hospital Medical Center in Cincinnati, Ohio, and the Medical University of South Carolina in Charleston, South Carolina. Children born on or after April 1, 2006, presenting with acute gastroenteritis and/or fever were considered. The eligibility description specifies vomiting and/or diarrhea of no more than 10 days’ duration. Demographic information, illness characteristics, and socioeconomic status were to be collected. Stool was to be collected within 14 days of symptom onset and tested at Cincinnati Children's Hospital Medical Center using Rotaclone; positive specimens were to be typed for common G and P serotypes.

The planned vaccine-effectiveness analyses compared 2 doses with 0 doses and 1 dose with 0 doses, using a subset of active-surveillance participants at least 52 days of age. The description explains that the minimum age was chosen in relation to the recommended age for a first dose, an allowance for receiving that dose, and time to mount an immune response. It does not report the matching variables or the detailed matching procedure. Allocation is not stated, and the groups are not a like-for-like randomized comparison.

The record identifies an endpoint titled “Matched VE Participants in the Minimum Age Model,” measured as a count of participants over 14 days from enrollment. It does not report the vaccine-effectiveness results, the numbers included in each dose comparison, or the model estimates and uncertainty. The sample-size justification, detailed statistical analysis plan, and procedures for handling missing data are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: 362 participants were enrolled in the overall study, which is stated in the protocol section. The participant totals in Models One and Two do not equal the overall number enrolled because some participants were included in both models.

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.

Population: Participants were included in the parent provided informed consent, if an adequate stool specimen was provided, the child was \<6 years of age, had symptoms \<10 days duration that were consistent with acute gastroenteritis.

6. Primary Endpoint

The registry lists the primary outcome as Matched VE Participants in the Minimum Age Model, measured over 14 days from the date of enrollment.

The named primary measure is a count of participants associated with the matched vaccine-effectiveness analysis in the minimum-age model. Its stated timeframe is 14 days from the date of enrollment. The record describes the underlying effectiveness question as comparing 2 RV1 doses with 0 doses and 1 dose with 0 doses among eligible surveillance participants who were at least 52 days of age.

A participant count is not itself a vaccine-effectiveness estimate. It describes how many participants are represented by the measure; an effectiveness estimate would summarize the association between vaccination and the outcome, with an uncertainty measure needed to assess precision. The registry record does not report the numeric result for this primary measure, the vaccine-effectiveness estimates, or confidence intervals. It therefore does not permit a reader to determine the direction or precision of the estimated association from the primary measure description alone.

The laboratory outcome was based on stool testing for rotavirus antigen, with positive specimens also intended for typing. Using laboratory-confirmed status to distinguish cases from controls provides an outcome definition based on testing rather than symptoms alone. In general, a clearly specified outcome helps make the comparison interpretable, but conclusions still depend on who entered the surveillance study, how vaccination was recorded, how matching was conducted, and how other differences between cases and controls were handled. Those analysis details are not reported in the registry record.

The minimum age is part of the stated analytic population, not a result. The record’s rationale links it to the timing of an initial dose and the period allowed for an immune response. It does not provide results for participants outside that minimum-age subset.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a case-control comparison estimate?

In a case-control study, participants are classified according to whether they have the outcome of interest. Here, the registry record defines cases by a positive stool test for rotavirus and controls by a negative stool test. Investigators then compare prior exposure—in this study, RV1 vaccination—between those outcome groups. This design is different from a randomized trial: vaccination is not assigned by the study, so the comparison is observational.

The stated effectiveness contrasts are 2 doses versus 0 doses and 1 dose versus 0 doses. Those contrasts can answer different questions, and each depends on the participants eligible for that particular analysis. The registry record does not report the exposure counts, estimates, or uncertainty for either contrast. It also does not specify the exact statistical measure used to calculate vaccine effectiveness or the details of the matched analysis. The title of the primary measure refers to matched vaccine effectiveness, but a title alone does not establish the model specification.

Why does matching matter?

Matching is a design or analysis approach used to make cases and controls more comparable on selected characteristics. For example, a study might match on characteristics that are related to both exposure and outcome; that is a general description, not a claim about which characteristics were used in this study. Matching can reduce imbalance on the factors chosen, but it does not automatically remove confounding from characteristics that were not matched or otherwise adjusted for. The factors used for matching, whether matching was individual or by groups, and how the analysis accounted for the matched structure are not reported in the registry record.

When observations are matched, the statistical analysis should reflect that structure. Treating matched observations as if they were entirely independent can misrepresent uncertainty. The appropriate approach depends on how matching was carried out and on the outcome and exposure data. Since those details are not reported, the adequacy or consequences of the matching analysis cannot be evaluated from the record.

What is the role of the minimum-age restriction?

The effectiveness analysis was described for participants at least 52 days of age. The record explains this threshold in relation to the recommended age for the first dose, an allowance for receiving that dose, and time for an immune response. Restricting the analysis to an age-eligible subset can make the comparison more aligned with the stated vaccination question. It also means the result, if reported, would pertain to that subset rather than automatically applying to all enrolled children. The number excluded by the age restriction is not reported in the registry record.

How should uncertainty be interpreted?

Statistical estimates are subject to sampling variability. A confidence interval describes uncertainty around an estimate under the assumptions of the statistical model. It is not a guarantee that the true value falls in the interval, and it does not address biases such as unmeasured confounding, selection into surveillance, or outcome misclassification. Those are general properties of statistical inference. For this study, the registry record does not report an estimate or confidence interval, so the precision of the effectiveness comparisons cannot be assessed.

A p-value, if reported, would summarize how compatible the observed data are with a specified null model under the analysis assumptions. It would not measure the probability that the null hypothesis is true, nor would it describe the size of an effect. No p-values or detailed hypothesis-testing plan for the vaccine-effectiveness comparisons are reported in the registry record.

What is over-dispersion, and is it relevant?

Over-dispersion is a general issue in count-data models: the data vary more than a model’s assumed distribution allows. If ignored when present, uncertainty estimates can be too small. The primary measure is described as a participant count, but the record does not report the analysis model or a dispersion estimate. It therefore does not establish whether a count model was used or whether over-dispersion was assessed. A count endpoint does not, by itself, show that a particular count-data method was applied.

What does the planning illustration mean?

A planning calculation can illustrate the sample size associated with an assumed effect and selected design assumptions. It is not a measure of the probability that this completed study found a statistically significant result. The stated illustration assumptions include a two-sided significance level of 0.05, equal allocation between arms, a normal approximation, and an effect to detect expressed as a fraction of the observed effect. No calculated planning values or observed effectiveness estimate are reported in the registry record. The illustration should therefore be treated as planning context, not as observed power or as evidence about the study result.

More generally, sample-size planning depends on the assumed effect, variability or event frequency, allocation, significance threshold, and analysis method. If the assumed effect is based on an observed estimate, that estimate may itself be uncertain. A planning calculation cannot replace reporting the analysis result and its uncertainty. The study’s own sample-size justification is not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The record describes two dose contrasts: 2 doses versus 0 doses and 1 dose versus 0 doses. It also describes testing and typing specimens, as well as several types of collected participant information. The registry record does not state how many analyses were prespecified, whether any outcomes or comparisons were prioritized for inference, or whether a method to address multiple comparisons was planned. Without that information, it is not possible to determine how multiplicity was considered or how it might affect interpretation of statistical significance.

Multiplicity is a general concern when several hypotheses are tested: the chance of at least one apparently unusual result can increase as the number of tests grows. Possible responses depend on the study aims and analysis plan. No correction method or hierarchy of tests is reported in the registry record, so none should be assumed. The presence of more than one stated dose comparison does not by itself show that a particular adjustment was required or used.

Details about missing observations are also not reported. The record does not say how many children lacked a stool specimen, had an unusable test, lacked vaccination information, or were excluded from the minimum-age analysis. It does not describe imputation, complete-case analysis, or sensitivity analyses for missing data. These omissions matter because the analysis population could differ from the enrolled population if information was incomplete or eligibility criteria removed participants.

The record describes active surveillance and enrollment of 362 participants, but it does not give a participant flow for the effectiveness analyses. The number contributing to each dose comparison, the number with complete information, and the reasons for any exclusions are not reported in the registry record. The analysis population should therefore not be inferred from the overall enrollment count alone.

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 registry record lists serious adverse-event figures separately for rotavirus-positive cases and rotavirus-negative controls. It reports 49 participants at risk in the positive group and 313 in the negative group. In both groups, the listed number with a serious event is 0, the number with another event is 0, and deaths are 0. No serious-event terms are listed.

These are descriptive registry counts, not a comparison of randomized treatment arms. The groups are defined by stool test results, and the record does not report serious events by vaccination status or dose. The figures therefore do not provide a safety comparison between vaccinated and unvaccinated participants.

The record does not explain how adverse events were solicited, what event definitions were used, how long participants were followed for safety, or whether reporting was complete. It also does not provide detail about which participants contributed to the at-risk counts. Consequently, the zeros should be understood only as the event counts posted for these groups, rather than as evidence that no events occurred under any possible definition or observation period. No broader safety conclusion can be drawn from these counts alone.

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

The study addresses a clinically relevant observational question: whether prior RV1 vaccination was associated with rotavirus-positive illness among children identified through active surveillance. It defines a laboratory-based case group and a test-negative control group, and it describes comparisons of 2 doses and 1 dose against 0 doses. This design and question are clear enough to understand the intended comparison.

The registry record does not report the actual vaccine-effectiveness estimates, confidence intervals, p-values, or dose-specific analysis counts. It therefore does not show whether the estimated association favored vaccination, how large an association was estimated, or how precisely it was estimated. The record also does not report the matching details or full statistical plan. Any conclusion about the direction, magnitude, or statistical significance of the effectiveness result would go beyond what is reported.

Even a reported association in this design would not, by itself, establish causation. Vaccination was not assigned at random, and outcome-defined groups can differ in characteristics related to both vaccination and rotavirus test status. Matching and statistical adjustment can address some measured differences, depending on their implementation, but cannot automatically eliminate unmeasured confounding or selection bias. The registry record does not provide enough analysis detail to assess those issues fully.

The participant count of 362 describes enrollment, not necessarily the sample included in each effectiveness analysis. The analysis was restricted to participants at least 52 days of age, and the record does not report how many participants met that criterion or had complete information for each comparison. The stated age threshold also limits the population to which a result from that model would directly pertain.

The serious-event counts are zero in the two listed groups, but the registry does not provide enough detail about safety ascertainment or follow-up to interpret these as a comprehensive safety finding. In short, the record documents the study question, surveillance approach, case-control grouping, and broad analysis contrasts. It does not provide the numerical effectiveness results needed to judge the observed association or its uncertainty.

13. Why This Trial Matters Statistically

This study is statistically instructive because it illustrates a common route for evaluating vaccine effectiveness when vaccination is observed rather than assigned: compare exposure histories among people with and without a laboratory-defined outcome. The case-control approach can focus analysis on outcome status, while the test-negative controls provide a comparison group drawn from the surveillance setting. Interpreting such a design requires attention to how participants entered the study and whether cases and controls were comparable.

The record also highlights why a named endpoint and a reported result are not interchangeable. “Matched VE Participants in the Minimum Age Model” is described as a participant count, while the substantive question concerns vaccine effectiveness. The count identifies a measure associated with the analysis, but without the model estimate and its uncertainty it cannot communicate the magnitude or precision of the effectiveness association.

The minimum-age restriction illustrates how an eligibility rule can define the population to which an analysis applies. The registry record explains its rationale in terms of vaccine-dose timing and time to mount an immune response. The resulting analysis would concern the eligible subset, not necessarily every participant enrolled through surveillance. Reporting the size and characteristics of that subset would help readers understand the evidence base for each comparison; those details are not reported in the registry record.

Finally, the study demonstrates the importance of transparent reporting for observational analyses. Matching can improve comparability on selected factors, but readers need to know what was matched, how the matched structure was analyzed, and what other adjustments were made. Missing-data handling, multiplicity decisions, and confidence intervals also inform how much weight to place on an estimate. These details and the numerical effectiveness findings are not reported in the registry record, so the design can be described but its statistical result cannot be evaluated.

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.

A central limitation of the available record is that it does not report the vaccine-effectiveness estimates or their uncertainty. The results cannot be assessed for magnitude, precision, or consistency across the 2-dose and 1-dose comparisons. The primary measure is described as a participant count, and the registry record does not provide its numeric result.

The study is observational rather than randomized. Vaccination was not assigned by the study, so differences between cases and controls could reflect factors other than vaccination. The record says that demographic information, illness characteristics, and socioeconomic status were collected, but it does not state which variables were included in matching or adjustment. The matching procedure and statistical model are not reported in the registry record. Residual confounding therefore cannot be assessed from the available description.

The surveillance narrative describes two sites, but its enrollment details focus on presentations to Cincinnati Children's Hospital Medical Center. How enrollment operated at the Medical University of South Carolina is not reported in the registry record. The description also does not report the number of children approached, the number eligible, or reasons for non-enrollment. Selection into surveillance and participation may affect how representative the analyzed group is.

The record does not report the number included in each dose comparison, the number meeting the minimum-age criterion, or how missing vaccination or stool-test information was handled. It also does not provide a participant-flow account, analysis plan, multiplicity approach, or sample-size justification. These omissions limit assessment of the analysis population and the robustness of the results.

Finally, the safety information gives group-level counts but not the methods or duration of adverse-event ascertainment. The zero counts should not be interpreted beyond the reported categories and groups. Together, these limitations mean that the registry record supports a description of the study framework, but not a complete appraisal of its effectiveness or safety findings.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effectiveness of Monovalent Rotavirus Vaccine (RV1) — NCT01871038.
• Registry record last updated 2026-01-26; status last verified 2026-01.
• Results first posted 2026-01-26.
• 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

NCT01871038, titled “Effectiveness of Monovalent Rotavirus Vaccine (RV1),” is a completed case-control study of Rotarix vaccine effectiveness. The record reports enrollment of 362 participants, a start of 2009-07, and primary completion in 2012-06. Active surveillance was described at Cincinnati Children's Hospital Medical Center and the Medical University of South Carolina.

Rotavirus-positive stool specimens defined cases and rotavirus-negative specimens defined controls. The planned effectiveness comparisons were 2 doses versus 0 doses and 1 dose versus 0 doses among participants at least 52 days of age. The named primary measure is a participant count for the matched minimum-age model, with a timeframe of 14 days from enrollment.

The record does not report the vaccine-effectiveness estimates, confidence intervals, detailed matching or modeling procedures, analysis populations, or missing-data methods. Serious adverse-event and death counts are listed as zero in both outcome-defined groups, without further ascertainment details. The design and intended questions are described, but the posted information does not permit evaluation of the numerical effectiveness findings.