Safety and Efficacy Trial of a Dapivirine Vaginal Matrix Ring in Healthy HIV-Negative Women: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Efficacy Trial of a Dapivirine Vaginal Matrix Ring in Healthy HIV-Negative Women (NCT01539226), a randomized na study. The primary outcome is HIV-1 Seroconversion According to Comprehensive HIV Testing Algorithm..

2. Clinical Question

The registry lists HIV infections as the condition and describes the trial as assessing safety and efficacy. It also names secondary questions concerning HIV-2 seroconversion, curable sexually transmitted infections, pregnancy, reported ring use and acceptability, and drug-resistance mutations among participants who acquired HIV-1. These outcomes address different aspects of the trial and should not be treated as interchangeable measures of the primary question.

3. Trial Design

The registry describes a multicentre, randomized, double-blind, placebo-controlled trial with a parallel-group design. The listed enrollment was 1959, and the status is completed. The start date was 2012-03-27 and the primary completion date was 2016-12-13. The phase is recorded as NA. The registry does not report the randomization procedure, the method used to maintain masking, or the planned allocation ratio.

Participants were assigned to a vaginal ring containing 25 mg of dapivirine or to a placebo vaginal ring containing 0.0 mg dapivirine. The primary outcome was HIV-1 seroconversion over 24 months, assessed with rapid and specialized laboratory testing according to the comprehensive HIV testing algorithm. The primary outcome population is described as all randomized participants, with an exclusion for people later found to have been HIV-1 infected at enrollment through HIV-1 RNA PCR testing despite not being identified as HIV-seropositive at the enrollment visit.

The registry reports 1302 participants in the dapivirine group and 650 in the placebo group for the primary outcome. The outcome-specific denominators differ across some secondary outcomes, so each result should be read with its own denominator rather than assuming one common analysis population for every measure. The reason for all denominator differences is not reported in the registry record.

The trial record names several secondary outcomes, including curable sexually transmitted infections, pregnancy, HIV-2 seroconversion, reported adherence, acceptability, and resistance mutations among participants who acquired HIV-1. Detailed numerical results are not posted for every named outcome. The original statistical analysis plan, sample-size justification, and trial-specific power assumptions 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: Participants who provided written informed consent at Screening Visit 1 were invited to undergo screening assessments for the trial. Participant screening was conducted over two scheduled Screening Visits with a maximum window period of 28 days between the two visits.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: This population consisted of all participants included in the ITT population (all randomised), excluding those who were not identified as HIV-seropositive at the Enrollment Visit, but who were later found to be already HIV-1 infected at enrollment through HIV-1 RNA PCR testing.

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 HIV-1 Seroconversion According to Comprehensive HIV Testing Algorithm., measured over 24 months.

The primary endpoint is the count of participants with HIV-1 seroconversion according to a comprehensive HIV testing algorithm. The registry describes the algorithm as using rapid and specialized laboratory testing and gives a timeframe of 24 months. It also defines the primary population as all randomized participants, excluding those later shown by HIV-1 RNA PCR testing to have already been infected at enrollment even though they were not identified as HIV-seropositive at the enrollment visit.

Seroconversion is used as an event-based endpoint to capture newly identified HIV-1 infection during the specified follow-up period. A comprehensive testing algorithm helps define how the event is determined; the registry does not give further operational details about the algorithm beyond the tests named. The outcome is reported as participant counts, and the comparison expresses the group difference in the proportions with an event. That makes the endpoint directly interpretable as the frequency of the recorded event in each group, while leaving the timing of individual events and the duration of exposure to risk unrepresented in the posted count comparison.

The endpoint addresses the trial’s central HIV-1 question, but it is not a complete summary of the trial. Secondary outcomes concern other infections, pregnancy, reported ring use and acceptability, and resistance findings. Safety outcomes are also presented separately. Each concerns a distinct outcome and may have a different denominator or interpretation.

7. Results Posted in the Registry

• Dapivirine Vaginal Ring: 6.3% (82/1302) versus 9.4% (61/650) on control; risk difference -3.1 percentage points (95% CI -5.7 to -0.5), risk ratio 0.67 (0.49–0.92); unadjusted two-proportion z-test p = 0.014.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

The Incidence of Curable STIs

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Dapivirine Vaginal Ring: 53.7% (682/1271) versus 50.5% (315/624) on control; risk difference 3.2 percentage points (95% CI -1.6 to 8.0), risk ratio 1.06 (0.97–1.17); unadjusted two-proportion z-test p = 0.193.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Dapivirine Vaginal Ring and the control. The interval gives the range of effects that remain compatible with the data.

Percentage of Participants With Pregnancy in Each Trial Arm Over the IP Use Period;

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Dapivirine Vaginal Ring: 3.3% (43/1306) versus 3.1% (20/652) on control; risk difference 0.2 percentage points (95% CI -1.4 to 1.9), risk ratio 1.07 (0.64–1.81); unadjusted two-proportion z-test p = 0.790.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Dapivirine Vaginal Ring and the control. The interval gives the range of effects that remain compatible with the data.

The Percentage of Participants With HIV-1 Drug Resistance Mutations Among Participants Who Acquire HIV-1.

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Dapivirine Vaginal Ring: 96.6% (84/87) versus 95.1% (58/61) on control; risk difference 1.5 percentage points (95% CI -5.2 to 8.1), risk ratio 1.02 (0.95–1.09); unadjusted two-proportion z-test p = 0.655.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Dapivirine Vaginal Ring and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes extend the record beyond HIV-1 seroconversion to other infections, pregnancy, reported use and acceptability, and resistance findings. The detailed numerical results available for curable sexually transmitted infections, pregnancy, and resistance among participants who acquired HIV-1 have intervals that include no difference. They do not establish that the groups are identical, and they do not reverse or confirm the primary finding. Each outcome addresses a separate question, with its own denominator and event definition.

The secondary results are best read as complementary context rather than as additional tests of the primary endpoint. Some outcomes concern events in the broader trial population, while the resistance outcome is restricted to participants who acquired HIV-1. Reported adherence and acceptability are also distinct from laboratory-confirmed infection outcomes. The registry names HIV-2 seroconversion, adherence, and acceptability, but detailed numerical results for these named measures are not reported in the registry record.

Unadjusted secondary comparisons carry less inferential weight when several outcomes are examined and no multiplicity strategy is reported. Without a stated testing hierarchy or adjustment, a nominal p-value for one secondary outcome does not automatically have the same confirmatory meaning as a prespecified primary comparison. The registry does not report adjusted secondary analyses or the original plan for interpreting these outcomes together. Their results can inform the overall description of the trial, but should not be treated as independent confirmation of the primary result.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• The Incidence Rate of HIV-2 Seroconversion.
• The Incidence of Curable STIs
• Percentage of Participants With Pregnancy in Each Trial Arm Over the IP Use Period;
• The Percentage of Women Who Report Adherence to the Use of the Vaginal Ring Inserted Once Every 4 Weeks Over the Trial Period;
• The Percentage of Women Who Report the Use of the Vaginal Ring as Acceptable;
• The Percentage of Participants With HIV-1 Drug Resistance Mutations Among Participants Who Acquire HIV-1.

9. Statistical Interpretation

10. Statistical Methods Explained

The registry presents the primary outcome as a binary event: each participant either had recorded HIV-1 seroconversion during the stated timeframe or did not. For such an outcome, a group proportion is the number of participants with the event divided by the number contributing to that outcome. The comparison can be expressed as a risk difference, which subtracts the placebo proportion from the dapivirine proportion. A negative value therefore indicates a lower observed event proportion in the dapivirine group. This is a general explanation of the measure; the registry’s posted estimate and uncertainty interval are the trial-specific results.

What does a risk difference describe?

A risk difference puts the contrast on the scale of the event proportions themselves. It answers how far apart the observed group proportions are, rather than describing a relative change. The scale retains the direction of the contrast: a value below zero means the dapivirine proportion is lower, and a value above zero means it is higher, given the stated group order. The primary estimate is negative. A risk difference does not describe the timing of events, and it does not explain the causes of any observed contrast.

How should the p-value be read?

A p-value measures how compatible the observed data are with a specified null model, under the assumptions of the statistical test. It is not the probability that the null hypothesis is true, nor is it a measure of the size or importance of an effect. The primary comparison’s posted p-value is unadjusted. The registry does not report the full test specification or an adjusted p-value. The p-value should therefore be read alongside the effect estimate and its confidence interval, not as a stand-alone verdict.

What information does a confidence interval add?

A confidence interval conveys uncertainty around an estimated contrast. Under the method’s assumptions, it gives a range of values compatible with the data at the stated confidence level. An interval that excludes zero for a risk difference indicates that the range does not include equal group proportions; an interval crossing zero leaves no difference among the values compatible with that interval. This does not mean that every value in the interval is equally plausible, nor does it account for analysis choices that are not described in the registry.

The primary interval lies below zero. The posted intervals for the detailed secondary comparisons cross zero. These patterns describe the precision and direction of the reported contrasts, but they do not establish that secondary outcomes are exactly equal between groups. The registry record does not give confidence intervals for the serious adverse-event counts.

Why do the analysis population and denominator matter?

The endpoint population determines which participants contribute to a result. For the primary outcome, the registry specifies all randomized participants with an exclusion for people later identified as already HIV-1 infected at enrollment. The arm denominators are the participants included for the outcome, not necessarily every person enrolled in the trial. The denominators listed for secondary outcomes vary, and the registry does not explain every difference. A count should therefore be interpreted together with its outcome-specific denominator and population description.

The resistance outcome is defined among participants who acquired HIV-1. Its denominator is not the full randomized group, so it answers a narrower question about resistance findings among those with HIV-1 acquisition. The curable sexually transmitted infection and pregnancy outcomes have their own listed denominators. Differences in these denominators can arise for reasons that the registry record does not specify; no cause should be assumed from the counts alone.

What does an unadjusted comparison leave open?

An unadjusted comparison describes the groups using the posted outcome data without a reported covariate adjustment. It does not necessarily account for baseline characteristics or other factors that an adjusted model might include. Whether adjustment was planned, how it would be carried out, and which analysis was considered primary in the original statistical plan are not reported in the registry record. The posted estimate should not be recast as an adjusted effect.

Multiplicity is another consideration. When several outcomes or comparisons are examined, the chance of at least one apparently notable result can increase if each is assessed separately without accounting for the collection of tests. The registry names multiple secondary outcomes, but does not report a multiplicity adjustment or a hierarchy that would define how to interpret them together. This is a general statistical caution, not evidence that any particular result is false.

These methods concepts help distinguish the reported event counts, the contrast between group proportions, and the uncertainty around that contrast. They do not fill gaps in the registry’s reporting. Details of missing-data handling, adherence-related analyses, interim analyses, and the trial’s own analysis plan are not reported in the registry record.

11. Confidence Intervals and Precision

The primary risk-difference confidence interval lies entirely below zero. This indicates that the interval’s compatible values all favor a lower observed event proportion in the dapivirine group on the stated difference scale. The interval still covers a range of possible magnitudes, so the point estimate should not be treated as exact. The posted unadjusted p-value is 0.014, but neither that value nor the interval conveys the consequences of unreported analysis decisions.

For the detailed secondary outcomes, the risk-difference intervals include zero. They therefore remain compatible with no difference as well as with differences in either direction. An interval that includes zero is not proof of equal group outcomes; it indicates that the data and stated interval method do not rule out the null value. The extent of uncertainty is also relevant, particularly when an outcome has fewer participants contributing to it, as with the resistance comparison among participants who acquired HIV-1.

Confidence intervals are useful because they show both direction and uncertainty, while a p-value alone does not show the range of effect estimates compatible with the data. Their interpretation depends on the method and analysis population. The registry does not report the full interval-construction method, adjusted estimates, or intervals for the posted serious adverse-event counts. The numerical precision of the posted results should therefore be understood as precision within the reported analysis, not as a complete account of all sources of uncertainty.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm for the binary outcomes, not total events. The listed assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The planning illustrations use the observed effect as a starting point and consider detecting the stated fraction of that effect. The trial’s own original design assumptions and sample-size justification are not reported in the registry record.

The 80% power column gives the planned number of participants per arm under which a study would have an 80% chance of detecting the specified effect if that effect were the true one and the planning assumptions held. The 90% power column describes the corresponding chance under the same assumptions at the larger power target. These are planning quantities for hypothetical future designs, not summaries of what happened in this trial.

Each planning row considers a different fraction of the observed effect. Planning for a smaller effect requires more participants, because smaller differences are harder to distinguish from random variation. The figures are sensitive to the assumed effect size and other assumptions; they should not be treated as universal enrollment targets. They are planning illustrations, not observed power. Observed power is not a useful substitute for interpreting the estimated effect and its confidence interval after a trial has been completed.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.094; treatment proportion p₁ = 0.063; average p̄ = 0.078.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.3802 = 0.7451.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.3795 = 0.3194.
4. n = (0.7451 + 0.3194)² / (-0.0309)² = 1,189.5, rounded up to 1,190 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.0938461538461538                          # control proportion
p1 <- 0.0629800307219662                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(1539226)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 1,190 (80% power), 1,592 (90% power)
 75% of observed effect: n per arm = 2,211 (80% power), 2,959 (90% power)
 50% of observed effect: n per arm = 5,187 (80% power), 6,943 (90% power)
power.prop.test: 1189.5 
Simulated power at n = 1,190 per arm: 0.806 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry names multiple secondary outcomes in addition to the primary HIV-1 seroconversion endpoint. Considering several outcomes creates a multiplicity issue: if each is tested separately without an adjustment or a prespecified hierarchy, the collection of results can be more likely to include a nominally notable finding by chance. This is a general statistical concern. The registry record does not report whether the trial used a multiplicity adjustment, a formal hierarchy, or another strategy for controlling interpretation across outcomes.

The detailed outcome comparisons are described as unadjusted, and no reported analyses are listed for the secondary outcome entries. The record does not provide an original statistical analysis plan, specify which secondary questions were confirmatory, or describe how the investigators intended to weigh the secondary findings relative to the primary endpoint. As a result, the posted secondary p-values and intervals should be interpreted as outcome-specific summaries rather than as a complete family of confirmatory tests.

Missing-data handling is not reported in the registry record. The record does not state how participants with incomplete outcome information were handled, whether any imputation was used, or how follow-up losses were incorporated. It also does not describe interim analyses or stopping rules. Those details should not be inferred from the final status or the posted endpoint counts.

The primary analysis population is described, including an exclusion for participants later found to have been infected at enrollment. Other population definitions and analysis-set rules are not fully described. The arm denominators differ across outcomes, but the reasons for all differences are not reported. These reporting gaps limit the ability to assess whether the same participants and assumptions underlie each result.

15. 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 2% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: febrile infection (0.2%), malaria (0.2%), cervical dysplasia (0.2%), headache (0.2%), respiratory tract infection (0.2%).

The registry lists 9 participants with serious adverse events among 652 at risk in the placebo group and 41 among 1306 at risk in the dapivirine group. It also lists other adverse events affecting 561 of 652 participants at risk in the placebo group and 1147 of 1306 at risk in the dapivirine group. Deaths are listed as 3 in the placebo group and 2 in the dapivirine group.

These are descriptive counts and denominators. They do not, on their own, establish whether an event was caused by the assigned ring or whether the groups differ after accounting for exposure and other factors. The registry lists febrile infection, malaria, cervical dysplasia, headache, respiratory tract infection, and tibia fracture among the top serious-event terms, each at 0.2%. The record does not provide a comparative statistical analysis or confidence intervals for these safety counts. The serious-event figures should therefore be read as reported safety information, not as a causal assessment.

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

The posted primary result describes a lower observed proportion of HIV-1 seroconversion in the dapivirine group than in the placebo group. Its risk-difference interval lies below no difference, and the registry reports an unadjusted p-value of 0.014. Those statistics characterize the recorded comparison over 24 months; they do not establish why the groups differed, nor do they capture every uncertainty about the trial’s conduct or analysis.

The result does not mean that every participant in one group had the same outcome, or that the observed group contrast predicts an individual participant’s outcome. It does not establish a mechanism of action, the effect of different patterns of ring use, or the result that would be obtained under a different population or study design. The registry does not report enough detail to assess those questions.

Secondary outcomes provide separate information, but their intervals include no difference and the registry does not report a multiplicity strategy. Some named outcomes lack detailed numerical results in the registry record. Safety counts are also descriptive and do not establish causality. The primary comparison should not be used to infer findings for these other outcomes.

The record is a source of posted trial results, not individualized medical guidance. It supports a statistical description of the reported endpoint and its precision, while leaving important questions about analysis plans, missing data, and the interpretation of multiple outcomes unresolved. The findings should be stated in terms of the measured population, endpoint, timeframe, and unadjusted comparison rather than generalized beyond those details.

17. Why This Trial Matters Statistically

This trial illustrates how a randomized, double-blind, placebo-controlled design can frame a direct comparison of event proportions between groups. The primary result is presented as counts, denominators, a risk difference, and an uncertainty interval. Reading these together distinguishes the direction of the observed comparison from the precision with which it is estimated. The interval’s position relative to zero adds information that a point estimate alone cannot provide.

It also illustrates why endpoint definitions and analysis populations matter. The primary endpoint is based on a comprehensive HIV testing algorithm, and the registry explicitly describes an exclusion for infections later identified as already present at enrollment. The secondary outcomes use different denominators and include a resistance measure limited to participants who acquired HIV-1. Those details affect what each comparison means.

Finally, the record demonstrates the limits of registry reporting. The posted results do not include the trial’s original sample-size justification, analysis plan, missing-data methods, or multiplicity approach. Planning illustrations can help explain how assumed effect sizes relate to required enrollment, but they cannot reconstruct the design rationale. Careful statistical interpretation therefore combines the reported estimates with attention to what the record does not describe.

18. 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 specific to this record constrain interpretation. The primary result is posted as an unadjusted comparison, and the registry does not provide the full analysis specification or an adjusted result. The original statistical analysis plan, sample-size justification, interim-analysis approach, and handling of missing data are not reported. The reasons for differences in denominators across outcomes are also not fully described.

The registry names more secondary outcomes than it gives detailed numerical results for. HIV-2 seroconversion, reported ring use, and acceptability are among the named outcomes for which detailed numerical results are not reported in the registry record. The detailed secondary comparisons that are posted have intervals including no difference, and no multiplicity strategy is stated. These reporting features limit how strongly the secondary outcomes can be used to support broader conclusions.

The primary endpoint is a participant count over 24 months, not a time-to-event comparison. The posted summary therefore does not describe event timing. The registry does not report confidence intervals or comparative analyses for the adverse-event counts, and the counts alone cannot establish causality. The resistance comparison is restricted to participants who acquired HIV-1, rather than representing the entire randomized population. These limitations concern the information available in the registry record and should not be filled in by assumptions about the protocol or analysis.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Safety and Efficacy Trial of a Dapivirine Vaginal Matrix Ring in Healthy HIV-Negative Women — NCT01539226.
• Registry record last updated 2022-10-19; status last verified 2022-07.
• Results first posted 2022-10-19.
• 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.

22. Record Summary

The registry describes a completed, multicentre, randomized, double-blind, placebo-controlled parallel-group trial of a dapivirine vaginal ring versus a placebo ring in healthy HIV-negative women. Enrollment was 1959. The primary outcome was HIV-1 seroconversion according to a comprehensive testing algorithm over 24 months, in a population defined by the registry with an exclusion for participants later found to have been infected at enrollment.

The posted primary comparison has a negative risk difference, a confidence interval below no difference, and an unadjusted p-value of 0.014. Detailed secondary outcomes and safety counts are also reported, but the record does not state the original analysis plan, multiplicity approach, or missing-data methods. Some named secondary outcomes lack detailed numerical results. The findings are therefore best interpreted within the outcome definitions and populations stated in the registry.