Journal of General Internal Medicine

, Volume 33, Issue 3, pp 253–255 | Cite as

High Adherence to HIV Pre-Exposure Prophylaxis among Veterans

  • Misha Huang
  • Wenhui Liu
  • Mary E. Plomondon
  • Allan V. Prochazka
  • Mary T. BessesenEmail author
Concise Research Reports


HIV AIDS Adherence Veterans 


HIV pre-exposure prophylaxis (PrEP) with daily oral tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) has been shown in clinical trials to be efficacious in preventing HIV infection in high-risk adults.1 Cases of failure and incident HIV infection in the major clinical trials were associated with poor medication adherence.2 Despite a large number of individuals who would benefit from PrEP use, concerns about poor medication adherence remain a barrier to wider dissemination of this intervention.3 Few studies have evaluated adherence to HIV PrEP in routine clinical settings. The Department of Veterans Affairs (VA) is the largest HIV care provider in the United States. PrEP is a covered benefit for all enrolled Veterans.


This was a retrospective cohort study of Veterans who initiated PrEP between July 2012 and June 2016, using data extracted from the VA clinical and administrative databases. PrEP adherence was measured as the proportion of days covered (PDC). PDC was calculated by dividing the total number of non-hospitalized days during which TDF/FTC was supplied, by the number of days in the observation period. Though previous studies have demonstrated that high PrEP efficacy may be achievable with 60% adherence,4 standard adherence measures in other clinical settings using pharmacy refill data define adherence as ≥80%.5 In this study, we defined <60% PDC as suboptimal, 60–79% PDC as acceptable, and ≥80% PDC as optimal adherence. Incident HIV infections were identified by screening records for HIV ICD-9 codes, ICD-10 codes, and HIV polymerase chain reaction (PCR) results. Diagnoses were confirmed with manual chart review.


We identified 1074 patients who initiated PrEP between July 2012 and June 2016. Among these, 989 had more than one medication fill and were included in our final cohort for analysis (Fig. 1).
Figure 1

Change in percentage of VA PrEP users with protective levels (acceptable or optimal) of adherence (≥ 60% PDC) over time.

The mean age of a patient starting PrEP was 41.5 years (SD 12.37), and the majority of this cohort were men (96%). Most initial PrEP prescriptions were prescribed by infectious disease specialists (72%), though 22% of PrEP was initiated by a primary care provider; these were similar for both adherent and non-adherent patients. The mean PDC was 83% for the entire cohort (SD 21%; Table 1).
Table 1

Demographic Characteristics of PrEP Users in the VA


Entire cohort

N = 989

Optimal adherence (≥80% PDC)

n = 674 (68.15%)

Acceptable or suboptimal adherence (<80% PDC)

n = 315

p value

Age, mean (SD), years

41.49 (12.37)

42.39 (12.40)

39.58 (12.11)


Sex, no. (%)




951 (96.16)

649 (96.29)

302 (95.87)



38 (3.84)

25 (3.71)

13 (4.13)


Race, no. (%)




613 (61.98)

444 (65.88)

169 (53.65)



225 (22.75)

122 (18.10)

103 (32.70)



151 (15.27)

108 (16.02)

43 (13.65)


Ethnicity, no. (%)




132 (13.35)

85 (12.71)

47 (14.92)



797 (80.59)

545 (81.46)

252 (80.00)



60 (6.06)

44 (5.83)

16 (5.08)


Rurality, no. (%)




887 (89.69)

598 (88.86)

289 (92.04)


 Rural/Highly rural

100 (10.11)

75 (11.14)

25 (7.96)


Provider specialty, no. (%)



 Infectious disease

712 (71.99)

489 (72.55)

223 (70.79)


 Primary care

222 (22.45)

149 (22.11)

73 (23.17)



55 (5.56)

36 (5.34)

19 (6.03)


VA facility type, no. (%)




115 (11.94)

77 (11.74)

38 (12.38)



848 (88.06)

579 (88.26)

269 (87.62)


Number of other chronic medications, no. (%)




679 (68.66)

448 (66.47)

231 (73.33)



310 (31.34)

226 (33.53)

84 (26.67)


Proportion of days covered, mean (SD)

0.83 (0.21)

0.95 (0.06)

0.57 (0.19)


*Data analyzed were at the time of the index TDF/FTC prescription (i.e., at the time of PrEP initiation)

PrEP pre-exposure prophylaxis, PDC proportion of days covered, CBOC/HCC community-based outpatient clinic/health care center,  VAMC VA Medical Center

We observed an increasing trend in PrEP adherence for each subsequent calendar year during which PrEP was initiated. In 2012, 75% of patients initiating PrEP achieved protective levels of adherence (≥ 60% PDC); this proportion rose to 90% of patients who started PrEP in 2016 (p = 0.004; Fig. 1). Fifty-six percent of patients achieved optimal adherence in 2012, and this proportion rose to 76% of patients who started PrEP in 2016 (p = 0.004).

In multivariable analysis, age, race, year of PrEP initiation, and number of other chronic medications were significantly associated with optimal adherence. Adherence increased by 9% per year for new PrEP starts (adjusted relative risk [aRR] 1.09; 95% CI 1.03, 1.15; p = 0.001). There were no differences in adherence between patients who were prescribed PrEP by an infectious disease provider versus primary care or other providers, between patients who initiated PrEP at a community-based outpatient clinic/health care center (CBOC/HCC) versus a VAMC, or between patients who lived in rural/highly rural areas versus urban areas. However, black race remained significantly associated with less than optimal (<80%) adherence, even after adjusting for covariates (aRR 0.76; 95% CI 0.66, 0.86; p < 0.001).

Six incident HIV infections were observed among our cohort. Three patients were diagnosed with HIV while on PrEP (0.3% of the cohort), and three were diagnosed after PrEP discontinuation. All three patients who seroconverted while on PrEP were diagnosed at their first 3-month follow-up. One reported missing several days of medication prior to an HIV exposure, and all three had M184V mutations (conferring resistance to FTC) on subsequent genotype testing.


PrEP adherence within the VA has increased in recent years, and current rates of adherence are high, with 90% of PrEP users achieving protective levels. However, black patients, who are already disproportionately affected by HIV, remain at risk for less than optimal adherence. Simplification of medication regimens in general may help promote better PrEP adherence. Few cases of HIV seroconversion occurred in patients while on PrEP. Overall, real-world adherence to PrEP has improved over time, and the vast majority of patients are at acceptable levels.





This study was supported by the Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, Health Services Research and Development Fellowship Program, the Denver-Seattle Center of Innovation, and the Colorado Clinical and Translational Sciences Institute at the University of Colorado. The funding source had no role in the design or conduct of the study; collection, management, analysis, or interpretation of the data; preparation, review, or approval of the manuscript; or the decision to submit the manuscript for publication. The content of this manuscript is solely the responsibility of the authors, and does not necessarily reflect the views or policies of the Department of Veterans Affairs or the United States Government.

Compliance with Ethical Standards

Prior Presentations


Conflict of Interest

All authors declare that they do not have a conflict of interest.


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Copyright information

© Society of General Internal Medicine (outside the USA) 2018

Authors and Affiliations

  • Misha Huang
    • 1
    • 2
  • Wenhui Liu
    • 2
  • Mary E. Plomondon
    • 2
    • 3
  • Allan V. Prochazka
    • 2
    • 3
  • Mary T. Bessesen
    • 1
    • 2
    Email author
  1. 1.Division of Adult Infectious DiseasesUniversity of Colorado DenverAuroraUSA
  2. 2.Department of Veterans Affairs Eastern Colorado Healthcare SystemDenverUSA
  3. 3.University of Colorado DenverAuroraUSA

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