Introduction

Pre-exposure prophylaxis (PrEP) for HIV prevention is a highly effective biomedical prevention medication and a proven and promising strategy for ending the HIV epidemic [1, 2]. Since its FDA approval in 2012, approximately one million people worldwide have benefitted from taking oral PrEP [3]. PrEP’s effectiveness is dependent on patients’ adherence to their chosen dosing strategy (e.g., daily or event-driven; with the most common strategy currently being daily oral PrEP in most countries), and on the health care systems’ ability to support sustained use over time (e.g., by providing flexible visit scheduling, payment navigation services, or other assistance) [4,5,6]. Despite significant strides in PrEP implementation over the past 5 years, data indicate that we are far from reaching UNAIDS goals on a global level [7], and reveal stark inequities in PrEP uptake in the United States by both geographic location and race/ethnicity [8]. Given these challenges in uptake, supporting adherence and sustainment for individuals who are willing to start PrEP is critical. Multiple studies have demonstrated the importance of regular adherence to ensure PrEP effectiveness among daily PrEP users [9, 10].

To date, there are equivocal data about PrEP adherence, with some studies demonstrating high adherence rates and others demonstrating lower adherence rates [11,12,13]. Researchers have identified sociodemographic factors that are correlated with PrEP adherence and continuation and demonstrate that many systemic barriers affect sustainment among racially, socioeconomically, and otherwise marginalized individuals [11, 13, 14]. In addition to these social determinants of health, many psychosocial and treatment-related factors, such as PrEP and HIV stigma, risk perception, side effects, and logistics of daily life, have been identified as predictors of PrEP adherence [15]. Because individuals with low adherence or who discontinue PrEP may be vulnerable to HIV infection [11, 14], it is crucial that research identify social and psychological factors that can actively promote and support PrEP adherence and sustainment. Although structural-level and organizational-level interventions are necessary to end the HIV epidemic, psychological factors continue to be an important focus for clinical interventions as well [16].

One of the most prominent psychological constructs across individual-level theories of health behavior change that is both intervenable and especially relevant for effective prevention is adherence self-efficacy [17]. Adherence self-efficacy is defined as confidence in one’s ability to adhere to a given treatment or medication [18,19,20], and has been demonstrated to be a strong predictor of adherence in a variety of contexts, including HIV treatment [21, 22]. In 2007, Johnson et al. published the HIV Treatment Adherence Self-Efficacy Scale (HIV-ASES), a twelve-item self-report scale to measure this construct [18]. The HIV-ASES has robust internal consistency and test–retest reliability [18] and has been used in over 250 studies both nationally and internationally [23,24,25]. While adherence self-efficacy is correlated with several factors that also affect medication adherence, such as depression [26, 27], this psychological construct is one of the strongest correlates of HIV adherence [21] and has been identified as a modifiable factor that clinicians can influence among patients to enhance adherence and care outcomes [28].

While adherence self-efficacy has been thoroughly explored in HIV treatment, few studies have included measures of PrEP self-efficacy [29,30,31] and none have been thoroughly validated through psychometric evaluation. In order to address this gap, our research team adapted the HIV-ASES for PrEP use and used this measure in two PrEP implementation research projects with populations disproportionately impacted by HIV in the United States [32, 33]. This paper presents an analysis of this adapted scale to evaluate its psychometric qualities and its association with PrEP adherence (i.e., daily use as directed) and sustainment (i.e., sustained use over time) in these two samples, to demonstrate the reliability and validity of this scale for the measurement of PrEP adherence self-efficacy in future research.

Methods

Participants

The analyses presented in this study are based on a total of 578 HIV-negative participants from two separate studies conducted in collaboration with Callen-Lorde Community Health Center, a federally qualified health center (FQHC) serving lesbian, gay, bisexual, transgender, and queer (LGBTQ) communities in New York City: SPARK, a PrEP demonstration-implementation project (Study A, N = 430), and FIRED UP, an observational cohort study of transgender women and trans feminine individuals (TGW/TFI) (Study B, N = 148).

Study Procedures: Study A

SPARK participants were recruited through medical provider or counselor referral at the health center. Eligibility criteria included: (1) being 18 years of age or older, (2) negative HIV status, (3) sex recorded at birth of ‘male,’ and (4) met CDC criteria for PrEP eligibility [34], and/or expressed concern about potential HIV exposure in the next 3 months. Participants who screened eligible for the study completed a self-administered online survey and then were scheduled for an in-person study enrollment visit at the health center at which they decided whether or not they wanted to begin PrEP. Data were collected between January 2014 and May 2017. Detailed information about the study protocol has been published previously [35].

Study Procedures: Study B

FIRED UP was designed to understand and improve PrEP implementation efforts with TGW/TFI in a real-world setting. Study staff embedded within the health center identified eligible patients with upcoming healthcare appointments, and conducted screening, informed consent, and enrollment procedures at appointments. Eligibility criteria included (1) being 18 years of age or older, (2) negative HIV status, (3) sex recorded at birth of ‘male,’ and (4) gender identity of woman, transgender woman, trans feminine, non-binary, two-spirit, or gender non-conforming. The study was divided into two cohorts: (1) TGW/TFI who were PrEP patients at the clinic and had been prescribed once daily tenofovir disoproxil fumarate/emtricitabine, and (2) TGW/TFI who were patients at the clinic but were not currently or previously prescribed or using PrEP. Data were collected from November 2018 to May 2020. Additional study procedure information is available in a previous publication [36].

Measures: Study A

Demographics

Participants reported their age, race/ethnicity, gender, sexual orientation, education, and income.

PrEP Adherence Self-Efficacy (PrEP-ASES)

Participants completed a 9-item adapted version of the HIV Adherence Self-Efficacy Scale (HIV-ASES) [18], measuring confidence in one’s ability to carry out behaviors important to PrEP adherence, even in the face of adherence barriers. The adaptation stayed as faithful as possible to the original scale, primarily replacing the words “your treatment” with the words “PrEP” or “taking PrEP,” (e.g., “Integrate your treatment into your daily routine” became “Integrate taking PrEP into your daily routine”). We deleted three scale items that referenced barriers or situations not relevant for PrEP (e.g., restrictions on meal timing or T-cell level drops). Response options ranged from 0 (“cannot do at all”) to 10 (“completely certain can do”)? Items were averaged for each participant, with higher scores indicating higher adherence self-efficacy. The full PrEP-ASES scale is presented in “Appendix”.

In Study A, all participants completed the PrEP-ASES at baseline (i.e., before initiating PrEP), and participants who initiated PrEP completed the scale on all follow up surveys. Since all participants were PrEP-naïve at baseline, the baseline PrEP-ASES scale prompt language was framed to reflect hypothetical use, whereas the scale prompt language for follow up surveys among active PrEP users referenced current PrEP use (see “Appendix” for different scale prompts).

The following measures were identified for inclusion in validity analyses based on hypothesized associations with adherence self-efficacy.

PrEP Uptake

After completing the baseline visit, participants decided whether they wanted to take PrEP. Those who elected to take PrEP were given a prescription for PrEP medications, based on which we created a binary variable of PrEP Uptake (Yes/No).

PrEP Sustainment

PrEP sustainment was defined through five separate binary variables: four pertaining to each follow up time point (3, 6, 9, 12 months), and one pertaining to the overall study period. Participants were coded as “Yes” for sustainment at each follow up time point during which they attended a visit and received and filled a PrEP prescription. We also created a variable for “on PrEP continually”, which was coded as “yes” if patients filled their prescriptions at 3, 6, and 9 months, and reported no interim PrEP cessations to clinicians or study staff between enrollment and their 12-month visit.

PrEP Adherence

Adherence was monitored using dried blood spot testing (DBS) at 3, 6, and 12-month follow-up visits. Results were dichotomized as TDF ≥ 700 fmol/punch versus lower levels, with the higher category having been found to indicate recent protective PrEP dosing, at ≥ 4 pills/week [37].

Perceived Sensitivity to Medications

At baseline, each participant completed the 5-item scale which assessed their sensitivity to medications [38]. Higher scores on this scale have been associated with greater experiences of medication side effects as well as greater intentional non-adherence to anti-retroviral therapy among individuals living with HIV [38, 39]. Response options ranged from 1 (strongly disagree) to 5 (strongly agree). Example item: “My body is very sensitive to medicines.” Individual items were averaged to provide a total score where higher scores indicate higher perceived sensitivity to potential adverse effects of medicines. The scale demonstrated good psychometric properties in the sample (α = 0.92).

Depressive and Anxious Symptoms

Participants completed two subscales of the Brief Symptom Inventory [40]. Specifically, participants completed the 6-item depressive and 6-item anxious symptoms subscales, which are part of the short (53-item) version of the Symptom Checklist 90-R. Both subscales demonstrated good psychometric properties in the current sample (anxious symptoms α = 0.87; depressive symptoms α = 0.88).

Measures: Study B

Demographics

Participants reported the same demographic information as in Study A.

PrEP Adherence Self-Efficacy (PrEP-ASES)

The same survey items were used to measure PrEP-ASES in Study B as were used in Study A. All participants completed the PrEP-ASES at enrollment, and participants who were PrEP users also completed the scale on follow up surveys. The survey prompt was worded to refer to hypothetical PrEP use in the non-PrEP cohort, and to refer to actual PrEP use in the PrEP cohort. See “Appendix” for prompt language.

The following measures were identified for inclusion in validity analyses based on hypothesized associations with adherence self-efficacy.

PrEP Rx Status

We created a binary variable based on PrEP prescription (Rx) status at enrollment. Participants with a PrEP prescription were coded as PrEP Rx = Yes, and participants who were neither current nor former PrEP users were coded as PrEP Rx = No.

Self-reported PrEP Adherence

Participants were asked a question from a self-report measure of medication adherence: “In the last 30 days, how often did you take your PrEP medication exactly as prescribed by your doctor?” (6-point Likert-type scale, ranging from “Never” to “Always”) [41]. In these analyses, this item was dichotomized into Always/Almost Always versus Usually/Sometimes/Rarely/Never.

PrEP Adherence: Urine TFV

Urine samples were collected from participants who reported having taken PrEP within the 7 days preceding their follow up study visit. Samples were analyzed using a liquid chromatography–tandem mass spectrometry (LC–MS/MS) urine assay with high sensitivity and specificity for tenofovir, performed by a third-party laboratory [42]. This assay has been validated, demonstrating high sensitivity and positive predictive value when compared to dried blood spots (DBS), as well as greater sensitivity than plasma-based measures [43,44,45]. It differentiates between high levels of urine TFV (> 1000 ng/mL), lower levels of urine TFV (10–1000 ng/mL), and the absence of detectable levels (< 10 ng/mL). High levels indicate having taken a pill in the last 7 days, and are a probable indicator for last pill within the last 2–3 days [43]. For these analyses, results are dichotomized as urine TFV > 1000 ng/mL vs. < 1000 ng/mL.

Perceived Sensitivity to Medications

Study B analyzed this construct using the same scale variable used in Study A.

Anxious Symptoms

Participants completed the Generalized Anxiety Disorder 7-item scale [46]. A total score is provided by summing ratings on a 4-point scale, 0 (not at all) to 3 (nearly every day). Example item: “Over the last 2 weeks, how often have you been bothered by the following problems? Feeling nervous, anxious or on edge.” Depressive symptoms were included in the survey; however, due to a survey programming error, the results for this scale were incomplete and could not be analyzed.

Resilience Scale

Participants completed the 25-item Connor–Davidson Resilience scale [47]. A total score is calculated by summing ratings on a 5-point scale, 0 (not true at all) to 4 (true nearly all the time). Example item: “Please indicate how much you agree with the following statement: I am able to adapt when changes occur.”

Data Analysis: Study A

First, we conducted an exploratory factor analysis (EFA) with data from a randomly selected sample of approximately half of the study participants. We used a principal axis factor method and oblique rotation (PROMAX) to assist us with identifying items with sufficient and adequate factor loadings (i.e., ≥ 0.40) [48, 49]. Factor retention was decided by examining eigenvalues, scree plot, and interpretability of factors. Specifically, factors with eigenvalues less than 1 and those with less than three items were not retained [48].

We then used MPlus 8.0 to conduct a Confirmatory Factor Analysis (CFA) of the 9-item scale with the data from the 225 baseline participants who did not overlap with the EFA sample. This sample size exceeded guidelines for deriving meaningful and interpretable models and fit indices in CFA [50]. Chi-square model fit criterion can lead to erroneous conclusions with criterion sensitivity to large samples (i.e., greater than 200), and has a tendency to indicate a significant probability level as sample size increases [51]. Therefore, model fit was evaluated by examining the root mean square error of approximation (RMSEA), the comparative fit index (CFI), and the standardized root-mean residual (SRMR). RMSEA values lower than 0.06, CFI values above 0.90, and SRMR values close to 0.08 all are indicative of good model fit [52]. We then conducted a CFA with only the participants who had adopted PrEP and completed the scale at their 3-month follow-up.

We assessed concurrent, predictive, and divergent validity, as well as test–retest reliability with all three PrEP-ASES time points (baseline, 3-months, and 6-months) in order to not only provide insight on PrEP-ASES in general, but also to better understand possible differences in the scale’s behavior among naïve vs. experienced PrEP users. For concurrent and predictive validity, we calculated mean PrEP-ASES scores stratified by binary PrEP use indicators, using independent t-tests to determine statistically significant differences. Baseline scores were stratified by PrEP uptake, and both baseline and follow up scores were stratified by sustainment and adherence indicators. We assessed divergent validity by calculating Pearson’s correlation coefficients and p-values between the three PrEP-ASES scores and the hypothesized correlates of adherence self-efficacy. To assess test–retest reliability, we calculated Pearson’s correlation coefficients and conducted a repeated measures ANOVA with post hoc pairwise comparison.

Data Analysis: Study B

We assessed concurrent, predictive, and divergent validity for PrEP-ASES in FIRED UP by applying the same analytic methods used for Study B. For concurrent and predictive validity, ASES scores were stratified by binary PrEP use indicators, including PrEP Rx status among all participants, self-reported adherence among PrEP users, and urine TFV level among PrEP users. For divergent validity, we ran correlations between PrEP-ASES T1, T2, T3, and three hypothesized adherence self-efficacy correlates (perceived sensitivity to medications, anxious symptoms, and resiliency). Correlations between the three ASES scores were also used to assess test–retest reliability.

Results: Study A

Sample Characteristics

Participants (N = 430) ranged in age from 18 to 76 years (M = 34.2, SD = 9.0). Table 1 presents the demographic characteristics of the study sample by PrEP Uptake. Cisgender men comprised 96% of the total sample, and 4% were transgender women or non-binary individuals. The sample was diverse in regard to race/ethnicity with 10.5% (n = 55) identifying as non-Hispanic Black, 11.9% (n = 51) identifying as Hispanic/Latino/a/x, 49.8% identifying as non-Hispanic white (n = 214), 18.8% identifying as multiracial (n = 81), and 6.6% identifying as Asian (n = 28). Approximately 75% of the sample identified as gay (n = 323), 12.6% identified as bisexual (n = 54) and 9.5% identified as queer (n = 41). Approximately two-thirds of the sample had earned a bachelor’s degree or higher and about two thirds also earned less than $50,000 annually. The only demographic correlate of PrEP uptake was gender identity, with a larger proportion of the PrEP decliners identifying as trans women, compared to PrEP adopters.

Table 1 Sample characteristics by study and PrEP status
Full size table

Construct Validity Analyses

Exploratory factor analysis from baseline data with the randomly selected half of the participants (n = 222) suggested that the one-factor model approximated multivariate normality as demonstrated by Kaiser–Meyer–Olkin value of 0.93 and a significant Bartlett’s test of sphericity: χ2(36) = 1765.34, p < 0.001. Factor retention was decided by examining eigenvalues, scree plot, and interpretability of factors, which all suggested a one-factor solution (eigenvalue = 6.78, 75.3% of variance explained).

The results of the CFA of the baseline data also suggested that a one-factor model provided acceptable fit to the data, χ2(27) = 146.75, p < 0.001, CFI = 0.93, RMSEA = 0.04, SRMR = 0.05. As illustrated in Table 2, items loaded significantly onto one factor and the scale demonstrated good psychometric properties in both samples (α = 0.95). Next, we fit a CFA to evaluate the one-factor solution among participants who decided to take PrEP at their 3-month follow-up visit, which also confirmed a one-factor model, χ2(27) = 163.62, p < 0.001, CFI = 0.90, RMSEA = 0.03, SRMR = 0.11.

Table 2 PrEP Adherence Self-Efficacy Scale: standardized factor loadings—SPARK (Study A)
Full size table

Concurrent and Divergent Validity

To assess concurrent validity, we examined whether PrEP-ASES assessed at baseline distinguished between those who elected to use PrEP compared to those who did not. Findings were in line with our hypothesis, such that those who elected to take PrEP had higher PrEP-ASES scores compared to those who did not elect to take PrEP. Additionally, we examined whether PrEP-ASES at baseline, 3-months (n = 280), and 6-months (n = 278) were associated with sustained PrEP use and adherence. In line with our hypothesis, we found that compared to those who stopped PrEP, those who sustained PrEP use had significantly higher PrEP-ASES scores at 3-months and 6-months. Similarly, participants who demonstrated higher levels of PrEP adherence (i.e., TDF ≥ 700 fmol) over the 12-months of the study had significantly higher PrEP-ASES scores at 3-months and 6-months compared to those with lower TDF concentrations. PrEP use indicators were not associated with a difference in baseline PrEP-ASES scores. Table 3 presents these data.

Table 3 Concurrent and predictive validity of PrEP-ASES—SPARK (Study A)
Full size table

Table 4 provides correlations of PrEP-ASES assessed at baseline, 3-months, and 6-months, and our divergent variables of interest. PrEP-ASES at all time points was negatively associated with Perceived Sensitivity to Medications and Depressive Symptoms assessed at baseline. Additionally, PrEP-ASES assessed at follow-up time points was negatively associated with Anxious Symptoms at baseline.

Table 4 Divergent validity of PrEP-ASES
Full size table

Test–Retest Reliability

We analyzed test–retest reliability among participants who initiated PrEP by first calculating Pearson’s correlation coefficients between PrEP-ASES at each time point. All three time points demonstrated a significant positive correlation with one another, and this association was strongest between the two follow up measurements (3-month and 6-month ASES r = 0.737, p < 0.001, compared to r < 0.35, p < 0.001, for baseline paired with either follow up time) (see Table 4).

In addition, we performed a repeated measures ANOVA (n = 266) to assess mean ASES scores at baseline and at the two times after accumulating PrEP experience. Mauchly’s test indicated that the sphericity assumption had been violated (χ2(2) = 69.74, p < 0.001), so we corrected degrees of freedom using Huynh–Feldt estimates of sphericity (ε = 0.82). The results showed that mean ASES scores significantly varied across the time points: F(1.63, 432.42) = 160.60, p < 0.001. Bonferroni post hoc tests indicated that in comparison to baseline PrEP-ASES (M = 7.85, SD = 1.23), scores were significantly higher at 3-months (M = 9.14, SD = 1.29, p < 0.001), and at 6-months (M = 9.09, SD = 1.36, p < 0.001). However, there was no significant difference between scores at 3-months and 6-months (p = 1). This aligns with our hypothesis that adherence self-efficacy would be higher after PrEP experience and indicates strong test–retest reliability among PrEP users (Data not shown).

Results: Study B

Sample Characteristics

Participants (N = 148) ranged in age from 18 to 65 years (M = 34, SD = 8.7). Demographic data stratified by PrEP Rx status is found in Table 1. Almost 88% of the total sample identified as trans women or women, with the rest identifying as trans feminine, non-binary, two-spirit, or gender non-conforming. The sample was diverse in regard to race/ethnicity with 16.2% (n = 24) identifying as non-Hispanic Black, 29.7% (n = 44) identifying as Hispanic/Latino/a/x, 25.7% identifying as non-Hispanic white (n = 38), and 22.3% identifying as multiracial (n = 33). Approximately 46% of the sample identified as straight (n = 68), 12.8% identified as bisexual (n = 19) and 10.8% identified as queer (n = 16). Only 28% of the sample had earned a bachelor’s degree or higher (n = 42), and 83.7% (n = 124) earned less than $50,000 annually. A greater proportion of participants who had received PrEP prescriptions at the health center identified as straight or queer compared to identifying as a lesbian or bisexual. A higher percentage of those with PrEP prescriptions were between the ages of 30–49, and a higher percentage of those who had not received PrEP prescriptions were aged 50 or older.

Concurrent and Predictive Validity

To assess concurrent validity, we examined whether PrEP-ASES at enrollment differed between those with PrEP prescriptions and those without. Findings supported our hypothesis, in that PrEP users had significantly higher T1 ASES scores. We also hypothesized that among those in the PrEP cohort, those with higher ASES scores at a given time point would have higher concurrent and future self-reported adherence and urine TFV, compared to those with lower ASES scores. Stratified ASES scores displayed patterns aligning with this hypothesis at all time points, some of which reached levels of statistical significance. Specifically, ASES T1 was significantly associated with self-reported adherence at T2 and T3, and with urine TFV at T3. ASES T2 was significantly associated with self-reported adherence at T2, and ASES T3 was significantly associated with both self-reported adherence and urine TFV at T3. Table 5 presents these data.

Table 5 Concurrent and predictive validity of PrEP-ASES—FIRED UP (Study B)
Full size table

Divergent Validity and Test–Retest Reliability

Overall, correlation coefficients between ASES scores and the hypothesized divergent variables were low (ranging from − 0.163 to 0.179). The T1 ASES has a small but significant negative correlation with Perceived Sensitivity to Medications, and a small marginally significant positive association with resilience. In terms of test–retest reliability, the correlations between the ASES scores over time ranged between 0.417 and 0.505 and were all statistically significant. These results are shown in Table 4.

Discussion

This paper is the first, to our knowledge, to develop and test an adapted PrEP adherence self-efficacy scale. In two studies conducted in a community-based health center with priority populations, we found evidence for the reliability and divergent validity of the PrEP-ASES, and for its ability to predict PrEP adherence and sustainment. The two studies differed in terms of the gender composition of the sample, the years of data collection, and the type of patient (patients offered free PrEP through the study, vs. patients engaging in regular healthcare that may or may not involve PrEP). The fact that results were replicated in these diverse samples bodes well for the potential generalizability of these findings to additional populations.

Our analyses suggested that PrEP self-efficacy is best conceptualized as a single factor. The original ASES was conceptualized as comprising two subscales: integration and perseverance; but past research also suggests the utility of a single factor or total score for this measure [28, 53]. In both studies, PrEP-ASES scores demonstrated good test–retest reliability, with correlations strengthening over time among the new PrEP users in Study A.

In Study A, the PrEP demonstration project, higher baseline PrEP-ASES scores predicted PrEP uptake, and higher PrEP-ASES scores 3 months after PrEP initiation were significantly associated with both PrEP adherence, measured by TDF-levels in DBS testing, and PrEP sustainment, measured by PrEP prescription pick-up. These significant associations were sustained at every time-point in the study, and PrEP-ASES scores at 3 months predicted continuous PrEP use over the full 12-month follow-up period. In Study B, the naturalistic PrEP cohort study, higher PrEP-ASES scores were associated with greater self-reported PrEP adherence, both concurrently and at future visits. Participants with urine TFV levels above 1000 had higher PrEP-ASES scores in every instance, but these associations did not always reach statistical significance.

Not surprisingly, PrEP-ASES scores were negatively associated with perceived sensitivity to medications, and this association was stronger at baseline, compared to follow-up, especially for participants in Study A who were initiating PrEP. The PrEP-ASES demonstrated divergence from other measures previously associated with adherence, including anxiety, depression and resilience.

Taken together, these results support the utility of the PrEP-ASES for use in PrEP-related research, as well as the importance of the concept of PrEP self-efficacy in clinical encounters. Many of the items in the PrEP-ASES represent abilities that can be taught or supported by behavioral interventions in health care settings. For example, patients can be taught strategies for integrating PrEP into their daily routines, for sticking to their PrEP schedule even when their daily routine is disruptive, and for navigating frustrations or negative emotions that might impact PrEP use. Research suggests that presenting patients with specific coping strategies can increase self-efficacy [54,55,56,57], which may have significant positive impacts on health behavior and outcomes. Using a consistent measure of PrEP self-efficacy may improve the evaluation of interventions aimed at increasing PrEP self-efficacy and enable researchers to understand the relative impact of different intervention strategies.

The analyses above are subject to several limitations. Although the studies were conducted with different patient populations and at different times, both were conducted in the same community-based health center in New York City. This community health center is a highly supportive environment for LGBTQ+ patients and has a robust PrEP program, so these findings might not necessarily generalize to differing patient populations or settings. Our studies did not include cisgender women and transgender men, who have both been systematically under-represented in PrEP prescriptions and programs. More research is needed on the psychological and social predictors of PrEP adherence and sustainment in these populations. It should be noted that longer-acting injectable cabotegravir has potential to mitigate adherence (though not sustainment) concerns; however, many individuals may find this option less desirable because of financial, logistic, or other concerns and may continue to elect oral PrEP.

Despite these limitations, these data indicate that the PrEP-ASES is a useful tool for understanding PrEP adherence and sustainment. Interventions and programs to support PrEP use in clinical settings should pay careful attention to the role of self-efficacy in patients’ behavior and should build upon strategies designed to enhance and support self-efficacy to ensure the success of PrEP in achieving Ending the Epidemic goals.