HIV VIRAL SUPPRESSION AND PRE-EXPOSURE PROPHYLAXIS IN HIV AND SYPHILIS CONTACT TRACING NETWORKS: AN ANALYSIS OF DISEASE SURVEILLANCE AND PRESCRIPTION CLAIMS DATA

Abstract

Background:

HIV and syphilis contact tracing networks offer efficient platforms for HIV treatment and prevention interventions, but intervention coverage within these networks has not been characterized.

Setting:

HIV and syphilis sexual contact tracing networks among men who have sex with men (MSM) in North Carolina (NC).

Methods:

Using surveillance data, we identified two types of “network events” occurring between January 2013 and June 2017 among NC MSM: being diagnosed with early syphilis or being named as a recent sexual contact of a person diagnosed with HIV or early syphilis. We estimated prevalent and incident HIV viral suppression among persons diagnosed with HIV before the network event, and we assessed the effect of contact tracing services on six-month cumulative incidence of viral suppression among previously HIV-diagnosed, virally unsuppressed persons. Using linked prescription claims data, we also evaluated prevalent and incident pre-exposure prophylaxis (PrEP) use in an insured subset of HIV-negative network members.

Results:

Viral suppression prevalence among previously HIV-diagnosed persons was 52.6%. The six-month cumulative incidence of viral suppression was 35.4% overall and 13.1 (95% CI: 8.8-17.4) percentage points higher among persons reached vs. not reached by contact tracing services. Few HIV-negative persons had prevalent (5.4%) or incident (4.1%) PrEP use in the six months before or after network events, respectively.

Conclusions:

Sub-optimal viral suppression and PrEP use among NC MSM in HIV/syphilis contact networks indicate a need for intensified intervention efforts. In particular, expanded services for previously HIV-diagnosed persons could improve viral suppression and reduce HIV transmission within these networks.

INTRODUCTION

Despite the development of highly effective HIV prevention modalities, HIV incidence is steady or increasing in many populations in the United States (US).¹ Available interventions, including antiretroviral therapy (ART) for people living with HIV (PLWH) and pre-exposure prophylaxis (PrEP) among HIV-negative persons, can substantially reduce HIV transmission.^2-5 However, ART and PrEP uptake and adherence are widely suboptimal,^6,7 preventing these interventions from reaching their full potential at the population level. New strategies are needed to increase ART and PrEP use for improved clinical and prevention outcomes.

For both epidemiological and practical reasons, sexual networks containing persons diagnosed with HIV and/or syphilis may be efficient platforms for HIV prevention interventions. HIV and syphilis often co-occur, particularly among men who have sex with men (MSM),⁸ and HIV-uninfected members of these networks experience heightened HIV risk.^9,10 Among persons with a previous HIV diagnosis and unsuppressed viremia, being diagnosed with early syphilis or named as a sexual contact of a person diagnosed with HIV or early syphilis suggests potential for ongoing HIV transmission risk.¹⁰ Because contact tracing for HIV and syphilis is routine in the US,¹¹ existing public health infrastructure can serve as a conduit for reaching HIV-positive and HIV-negative network members with ART and PrEP, respectively.

Estimates of HIV viral suppression and PrEP use within HIV/syphilis networks are required to identify resource needs and coverage gaps for enhanced intervention design. Using communicable disease surveillance data linked to prescription claims data, we evaluated prevalent and incident viral suppression and PrEP use in the HIV/syphilis contact tracing network among MSM in North Carolina (NC).

METHODS

Data Sources & Study Populations

We identified our study population within the NC Electronic Disease Surveillance System (NC EDSS), housed at the NC Division of Public Health (DPH).¹² NC EDSS hosts personal, laboratory, medical, and contact tracing data for reportable communicable diseases in NC, including HIV and syphilis.¹² Contact tracing data in NC EDSS are collected by Disease Intervention Specialists (DIS) who interview persons newly diagnosed with HIV or early (primary, secondary, or early latent) syphilis to identify recent sexual and injection drug use contacts. DIS elicit contacts during the twelve months before DIS interview for persons newly diagnosed with HIV¹³ and during the three, six, and twelve months before symptom onset for persons diagnosed with primary, secondary, and early latent syphilis,¹⁴ respectively. DIS then trace and test these named contacts for both infections.

We first identified all persons becoming diagnosed with HIV or early syphilis in NC between January 2013 and June 2017 (inclusive) within NC EDSS. We then identified the sexual partners named by these persons during contact tracing. We defined a qualifying HIV/syphilis network event as receiving an early syphilis diagnosis or being named as a sexual contact by a person newly diagnosed with HIV or early syphilis. Some persons experienced multiple network events during the study time frame; all such events were included. We further restricted our study population to include only persons who: 1) were ≥18 years old at the network event; 2) had a NC address documented at the time of the network event; 3) did not self-identify as transgender; and 4) either self-identified as MSM or identified as male and were named as a sexual contact by a self-identifying male partner. Self-identified transgender individuals were excluded because gender identity was unavailable for persons diagnosed with syphilis during the study period, preventing subgroup analyses of transgender populations. Persons <18 years of age were excluded because claims data for assessing PrEP use (see below) were available only for those ≥18 years of age, and we sought to establish a consistent age cut-off for all analyses.

We then identified sub-populations for viral suppression and PrEP use analyses. Viral suppression analyses were conducted only among persons with an HIV diagnosis ≥30 days before their network event. Persons diagnosed with HIV at the network event or <30 days prior were excluded because they could not yet have achieved suppression through ART. In sensitivity analyses, we allowed a longer time to prevalent suppression by restricting to persons diagnosed ≥90 days before the network event. Incident viral suppression analyses included only previously HIV-diagnosed persons without prevalent viral suppression at their network event.

For analyses of prevalent and incident PrEP use, persons with confirmed HIV-negative or unknown HIV status at the time of the network event were first linked to insurance claims data from the largest commercial insurer in NC, covering approximately 60% of the privately insured population [Supplemental Table 1]. We included only those individuals in NC EDSS who were enrolled in a commercial insurance plan with prescription coverage over the relevant time frames (specified below). As most persons without a prior HIV diagnosis are tested for HIV at the time of a network event (but negative results are not always documented), persons without an HIV diagnosis on record in NC EDSS before or in the 14 days after the event were presumed HIV-negative. We interrogated the impact of this assumption in a sensitivity analysis limiting PrEP analyses to events among persons who 1) were reached by DIS at the network event, consented to HIV testing, and had a documented negative result; OR 2) had an unrelated, documented HIV-negative test result in NC EDSS in the three months before the network event or ever after the network event, through December 2019.

Data were extracted from NC EDSS using SAS 9.4 (SAS Institute Inc., Cary, NC) and analyses were conducted in SAS 9.4 and R v. 3.5.0.¹⁵ The Non-Biomedical Institutional Review Board at UNC-CH approved this study.

Analyses

Prevalent and Incident Viral Suppression among Previously Diagnosed PLWH

HIV viral load is routinely measured during HIV clinical care visits to evaluate disease progression and treatment success. In NC, HIV viral load measures generated by HIV care providers are mandatorily reported to NC DPH.¹³ We identified all viral load measures during the year before or at each network event among previously diagnosed PLWH to assess prevalent viral suppression. Using the measure collected closest to the event, we classified persons with viral load <200 copies/mL as virally suppressed and persons with viral load ≥200 copies/mL as not virally suppressed.¹⁶ Persons with no viral load measures in the year before the network event (20.6% of previously diagnosed PLWH) were assumed to be out of care and classified as not virally suppressed. We believe this assumption reasonable because all persons included in our analyses had a NC address documented by DIS at the time of their network event, and mandatory reporting of all viral load measures to DPH ensures capture of this HIV care proxy. As such, persons without a viral load measure in the prior year were unlikely to have received recent care, and were thus unlikely to have been virally suppressed. Virally non-suppressed PLWH were subsequently assessed for six-month cumulative incidence of viral suppression, defined as ≥1 viral load measure <200 copies/mL in the six months after the event. In an ancillary analysis, we assessed the twelve-month cumulative incidence of viral suppression, defined analogously.

Effect of DIS Services on Incident Viral Suppression

To assess the impact of DIS services on viral load outcomes among previously diagnosed PLWH in our population, we estimated the effect of being reached by DIS in association with the network event on the six-month cumulative incidence of viral suppression thereafter. Previously diagnosed PLWH were classified as reached by DIS services if DIS interacted with them in any capacity, including contact tracing interviews for those diagnosed with early syphilis, re-interviews among those named as contacts of persons diagnosed with HIV, and contact interviews for syphilis screening among those named as contacts of persons diagnosed with early syphilis. We applied linear risk regression to estimate adjusted cumulative incidence differences (aCID) comparing incident viral suppression among those reached vs. not reached by DIS. A generalized estimating equations (GEE) model with an autoregressive correlation structure was used to account for the presence of multiple observations for some persons.¹⁷

Plausible confounders of the possible effect of DIS services on incident viral suppression were identified through a comprehensive literature review and assessed using a directed acyclic graph (DAG).¹⁸ Confounders in the minimally sufficient adjustment set were then evaluated to identify optimal functional form, resulting in nominal coding of event year (2013, 2014, 2015, 2016, 2017), network event status (syphilis diagnosis, HIV contact, syphilis contact), and age at network event (18-24, 25-34, 35-44, ≥45 years), and restricted cubic splines to represent years since HIV diagnosis. This adjustment set was included in the linear risk GEE model to estimate an aCID with robust standard errors using the sandwich estimator. GEE models were repeated with twelve-month cumulative incidence of viral suppression as the outcome. Further GEE modeling details are supplied in the Supplemental Materials.

Prevalent and Incident PrEP Use among Commercially Insured, HIV-Negative Persons

PrEP use, as measured by emtricitabine and tenofovir disoproxil (FTC/TDF) prescription claims, was evaluated among the commercially insured subset of HIV-negative persons using an adaptation of a previously described algorithm for PrEP utilization.¹⁹ Persons prescribed FTC/TDF, also known as Truvada, for PrEP were identified via exclusion of FTC/TDF prescriptions for HIV or Hepatitis B virus treatment or as HIV post-exposure prophylaxis (PEP) [Figure 1]. PrEP prescriptions and exclusions due to prior or concomitant prescriptions and/or diagnoses were determined from International Classification of Diseases, Ninth and Tenth Revisions Clinical Modification (ICD-9/10-CM) codes and National Drug Codes (NDC) in insurance claims data¹⁹ [Supplemental Table 2]. Claims records were queried from January 1, 2010 through 30 days after FTC/TDF prescription as an “all-available” lookback period to identify exclusions. We manually reviewed all records for each event with an FTC/TDF claim excluded due to prior HIV diagnosis, identifying and correcting erroneous ICD-9/10-CM codes for prior HIV diagnosis in two persons who tested HIV-negative at the network event and indicated to DIS that they were currently using PrEP.

Figure 1.

Algorithm for identification of emtricitabine and tenofovir disoproxil fumarate (FTC/TDF) prescribed for pre-exposure prophylaxis (PrEP) against HIV. Specific ICD-9/10-CM and NDC codes used in this algorithm are detailed in Supplemental Table 2.

We assessed prevalent PrEP use, defined as ≥1 PrEP prescription claim in the six months before the network event, among those with continuous pharmacy insurance coverage during that period. We then assessed incident PrEP use after a network event among all persons with pharmacy insurance coverage over the sixty days before the event date and continuously for six months after the event date, excluding persons with documented PrEP use before the network event. Six-month cumulative incidence of PrEP use was defined as ≥1 PrEP prescription claim in the six months after the network event.

We described prevalent and incident PrEP use by age, self-identified race/ethnicity, HIV/syphilis network event status (syphilis diagnosis, HIV contact, syphilis contact), year of network event, insurance subscriber (self, parent, other), and apparent PrEP indication. As detailed in the Supplemental Materials, we defined PrEP indication at the time of the network event as: 1) ≥1 male sex partner in the prior six months documented in NC EDSS; AND either 2a) condom use during the contact tracing period documented as anything other than “Always” OR 2b) diagnosed with or self-reported a bacterial sexually transmitted infection (STI) in the prior six months.

RESULTS

We identified 3,963 eligible early syphilis diagnoses and 8,456 HIV/syphilis contact events under our inclusion criteria [Figure 2]. Of these network events, 4,959 occurred among 2,970 previously diagnosed PLWH and 6,975 occurred among 5,245 confirmed or presumptively HIV-negative persons. Previously diagnosed PLWH were older (median age: 31.1 vs. 27.3) and more likely to self-identify as Black, non-Hispanic (71% vs. 54%) than HIV-negative persons, who were more likely to be reached by DIS after a network event (85% vs. 68%).

Figure 2.

Analysis populations. HIV/syphilis network events among adult, cisgender, North Carolina (NC)-residing men who have sex with men (MSM), January 2013 – June 2017, were identified from NC surveillance data. Previously diagnosed people living with HIV (PLWH) were evaluated for prevalent and incident viral suppression. HIV-negative persons were matched to insurance claims data and evaluated for prevalent and incident PrEP use. Some HIV-negative persons were eligible for both prevalent and incident PrEP use analyses. *Events among HIV-negative persons, defined as those with no HIV diagnosis on record in NC EDSS at any point before or in the 14 days after the event. ⁺Events among previously diagnosed PLWH, defined as those with an HIV diagnosis on record in NC EDSS ≥30 days before the event. ^#Events among recently diagnosed PLWH, defined as those with an HIV diagnosis on record in NC EDSS <30 days before or ≤14 days after the event. ^{^}Population for prevalent PrEP use analysis was restricted to events among persons with continuous pharmacy coverage during the six months before the network event. **Population for incident PrEP use analysis was restricted to events among persons with continuous pharmacy coverage throughout the sixty days before and the six months after the network event, excluding persons with prior PrEP use.

Viral Suppression among Previously Diagnosed PLWH

Approximately half (52.6%; N = 2,609/4,959) of all events among previously diagnosed PLWH occurred among persons who were virally suppressed according to surveillance records [Table 1]. Incident viral suppression in the six months after the event was then documented for 35.4% (831/2,350) of events among previously diagnosed PLWH without prevalent viral suppression. Among events without incident viral suppression, 38% had a documented viral load ≥200 copies/mL in the six months following the event and 62% had no documented viral loads during this time frame. The six-month cumulative incidence of viral suppression among persons reached by DIS was 40.4% (564/1397), compared with 28.0% (267/953) among those not reached. After adjustment for potential confounders, the six-month cumulative incidence of viral suppression among persons reached by DIS was 13.1 (95% CI: 8.8, 17.4) percentage points higher than that observed among persons not reached by DIS. Few persons (n=192) were included in incident viral suppression analyses due to a network event ≥30 and <90 days after HIV diagnosis, and the six-month viral suppression aCID was not substantially changed in sensitivity analyses excluding these persons [aCID = 12.3 (95% CI: 7.8 - 16.8)].

Table 1.

Individual characteristics by HIV viral suppression at the time of an HIV/syphilis network event occurring January 2013 – June 2017 in North Carolina among men who have sex with men who were previously diagnosed with HIV.

Individual characteristics	Prevalent viral suppression*	Not virally suppressed
		Incident viral suppression+	No incident viral suppression
Total network events	2609	831	1519
Years since HIV diagnosis (median, IQR)	5.5 (2.4, 9.8)	4.2 (0.8, 8.2)	4.8 (2.1, 8.6)
Age at network event (median, IQR)	33.2 (27.6, 44.2)	29.8 (25.8, 38.3)	28.9 (24.9, 35.8)
Race/ethnicity (N, %)
White, non-Hispanic	717 (27.5)	182 (21.9)	220 (14.5)
Black, non-Hispanic	1690 (64.8)	582 (70.0)	1233 (81.2)
Hispanic	144 (5.5)	44 (5.3)	41 (2.7)
Other	38 (1.5)	12 (1.4)	6 (0.4)
Missing	20 (0.8)	11 (1.3)	19 (1.2)
Network event
Syphilis diagnosis	1165 (44.6)	289 (34.8)	425 (28.0)
HIV contact	537 (20.6)	260 (31.3)	555 (36.5)
Syphilis contact	907 (34.8)	282 (33.9)	539 (35.5)
Reached by DIS#	1951 (74.8)	564 (67.9)	833 (54.8)
Year
2013	200 (7.7)	87 (10.5)	242 (15.9)
2014	410 (15.7)	158 (19.0)	297 (19.6)
2015	820 (31.4)	229 (27.6)	428 (28.2)
2016	818 (31.4)	266 (32.0)	376 (24.8)
2017++	361 (13.8)	91 (10.9)	176 (11.6)

IQR; interquartile range

^*≥1 viral load <200 copies/mL in the 12 months before the date of the syphilis diagnosis or the date named as an HIV or syphilis contact

⁺≥1 viral load <200 copies/mL in the 6 months after the date of the syphilis diagnosis or the date named as an HIV or syphilis contact

^#Disease Intervention Specialist; refers to DIS contact after a network event, not the time of the previous HIV diagnosis

⁺⁺January 1, 2017 – June 31, 2017

Viral suppression within twelve months was documented for 49.1% (1,154/2,350) of events among previously diagnosed PLWH without prevalent viral suppression. The aCID comparing twelve-month incident viral suppression among those reached vs. not reached by DIS was 6.7 (95% CI: 2.1, 11.3) percentage points [unadjusted cumulative incidence = 53.7% (750/1397) in those reached vs. 42.4% (404/953) in those not reached].

PrEP among Commercially Insured, HIV-Negative Persons

Of the 5,245 HIV-negative persons with network events, 1,788 (34.1%) were successfully linked to insurance claims data with any coverage in the period January 2010 – December 2017. Among these persons, 441 HIV/syphilis network events occurred among 372 persons with pharmacy coverage at and during the six months before the event for analyses of prevalent PrEP use. No FTC/TDF prescriptions were excluded as treatment for HIV or HBV or as PEP. We identified prevalent PrEP use for 5.4% (24/441) of these network events. Assessment of incident PrEP use was conducted with 411 network events among 360 persons without prevalent PrEP use who had pharmacy coverage during the sixty days before the event and continuously for six months after the event. No FTC/TDF prescriptions were excluded as treatment for HIV or HBV, while three prescriptions were excluded as PEP. Six-month cumulative incidence of PrEP use following an HIV/syphilis network event was 4.1% (17/411).

Small increases in prevalent and incident PrEP use were observed from 2013 to 2017, but PrEP use remained low throughout this period [Table 2]. Persons who self-identified as White, non-Hispanic and persons who were diagnosed with early syphilis were overrepresented within the population matched to insurance claims data, particularly among those with prevalent PrEP use. Prevalent PrEP users were older than those without prevalent PrEP use (median age = 34.4 vs. 28.2 years), while incident PrEP users were younger than those without (24.9 vs. 28.1 years). Most network events among HIV-negative persons (82.7%; N = 5,768) occurred among those indicated for PrEP under our surveillance-based definition, and most incident PrEP use (88%; 15/17) occurred among indicated persons. Six-month cumulative incidence of PrEP use among indicated persons was 4.5% (15/337).

Table 2.

Individual characteristics by pre-exposure prophylaxis (PrEP) use at the time of an HIV/syphilis network event and in the subsequent six months among HIV-negative men who have sex with men in North Carolina, January 2013 – June 2017. PrEP use is assessed only among persons linked to a large commercial insurer in NC with pharmacy coverage during the study period.

Individual characteristics	All events among HIV-negative persons	Prevalent PrEP use*		Incident PrEP uptake+
		Yes	No	Yes	No
Total	6975	24	417	17	394
Age at event (median, IQR)	27.3 (23.2, 35.3)	34.4 (26.8, 39.6)	28.2 (23.1, 38.0)	24.9 (20.6, 32.2)	28.1 (23.2, 38.1)
Race/ethnicity (N, %)
White, non-Hispanic	2411 (34.6)	16 (66.7)	230 (55.2)	9 (52.9)	201 (51.0)
Black, non-Hispanic	3783 (54.2)	5 (20.8)	153 (36.7)	5 (29.4)	161 (40.9)
Hispanic	487 (7.0)	<5#	16 (3.8)	<5	14 (3.6)
Other	124 (1.8)	<5	12 (2.9)	<5	14 (3.6)
Missing	170 (2.4)	<5	6 (1.4)	<5	<5
Network event status
Syphilis diagnosis	1839 (26.4)	9 (37.5)	123 (29.5)	8 (47.1)	113 (28.7)
HIV contact	2235 (32.0)	<5	120 (28.8)	<5	117 (29.7)
Syphilis contact	2901 (41.6)	11 (45.8)	174 (41.7)	5 (29.4)	164 (41.6)
Reached by DIS	5951 (85.3)	23 (95.8)	378 (90.7)	16 (94.1)	357 (90.6)
Year
2013	938 (13.5)	<5	43 (10.3)	<5	46 (11.7)
2014	1282 (18.4)	<5	88 (21.1)	<5	94 (23.9)
2015	1968 (28.2)	6 (25.0)	125 (30.0)	<5	98 (24.9)
2016	1827 (26.2)	11 (45.9)	101 (24.2)	9 (52.9)	94 (23.9)
2017**	960 (13.8)	<5	60 (14.4)	6 (35.3)	62 (15.7)
Insurance subscriber
Self	---	23 (95.8)	342 (82.0)	13 (76.5)	327 (83.0)
Parent	---	<5	71 (17.0)	<5	62 (15.7)
Other	---	<5	<5	<5	5 (1.3)
Indicated for PrEP	5768 (82.7)	18 (75.0)	337 (80.8)	15 (88.2)	322 (81.7)

IQR; interquartile range. DIS; Disease Intervention Specialist

^*Defined as ≥ one insurance claim for emtricitabine and tenofovir disoproxil fumarate (FTC/TDF) prescribed for ≥30 days in the six months before the date of the event

⁺Defined as ≥ one insurance claim for emtricitabine and tenofovir disoproxil fumarate (FTC/TDF) prescribed for ≥30 days in the six months after the date of the event

^#Cell sizes <5 are not presented to prevent deductive identification.

^**January 1, 2017 – June 31, 2017

In a sensitivity analysis restricting PrEP analyses to persons with documented HIV-negative status to estimate upper bounds for PrEP use, the size of the initial population for PrEP analyses was reduced from 6,975 to 5,787 events. After matching to insurance claims data, 44/441 (10.0%) events were excluded from prevalent PrEP use analyses and 41/411 (10.0%) events were excluded from incident PrEP uptake analyses. The prevalence of PrEP use was 5.8% and the six-month cumulative incidence of PrEP uptake was 4.3% in this restricted population.

DISCUSSION

Combination ART and PrEP interventions with high levels of uptake and adherence are required to end the HIV epidemic,^20,21 and sexual networks with prevalent HIV and syphilis are high-priority populations for such programming. However, current levels of coverage in these networks are not well characterized. To assess resource needs and inform intervention planning in this population, we evaluated prevalent and incident viral suppression and PrEP use among MSM diagnosed with early syphilis or named as sexual contacts of persons diagnosed with HIV or early syphilis in NC, finding low levels of all outcomes.

Presentation of viremic, previously diagnosed PLWH in the HIV/syphilis network is a critical opportunity to activate support for care engagement or re-engagement. An estimated 70% of HIV transmissions in the US²² (and 77% in NC)²³ arise from contact with previously diagnosed PLWH, highlighting the importance of reaching this population with suppressive ART for clinical and public health benefits. In our population, 31% of all early syphilis diagnoses and HIV/syphilis contact events occurring among previously diagnosed PLWH were among persons with unsuppressed viremia at the event and for six months thereafter. These events represent missed opportunities to leverage a syphilis diagnosis or HIV/syphilis contact event as a springboard to viral suppression.

Although incident viral suppression after network events was low, existing public health services offer a potential route for improvement. We observed a significant increase in six-month cumulative incidence of viral suppression among persons reached by DIS in comparison to those who were not reached. DIS services may act as a “cue to action” for ART use under the Health Belief Model²⁴ by reinforcing potential health, transmission, and legal consequences associated with unsuppressed viremia, as well as a channel to care engagement services. Because the highest-priority responsibilities of DIS are to interview newly diagnosed persons and screen their contacts for infection, only 59% of previously diagnosed PLWH with unsuppressed viremia in this study population were reached by DIS. Higher coverage of DIS services among previously diagnosed PLWH may facilitate attainment of 2020 National HIV/AIDS Strategy targets of 90% care engagement and 80% viral suppression among diagnosed PLWH.²⁵

PrEP is indicated for a large population on the basis of HIV exposure risk,²⁶ but uptake has been poor. In the US, only an estimated 18% of the 1.2 million persons indicated for PrEP²⁷ were prescribed PrEP in 2018.⁷ In NC, just an estimated 2,500 persons were prescribed PrEP in 2018.²⁸ We observed very high levels of PrEP indication in our study population, but little PrEP use in the commercially insured subset we analyzed, possibly reflecting difficulties accessing PrEP in NC during the study time frame. However, prevalent and incident PrEP use trended upward from 2013 to 2017, demonstrating increased PrEP awareness, interest, and access in this population since its introduction in 2012.²⁹ Persons with incident PrEP use after a network event were substantially younger than prevalent PrEP users, suggesting that the contact tracing network may be a valuable pathway for reaching at-risk young MSM with PrEP.

NC and several other jurisdictions have recently expanded HIV prevention services to include referrals for PrEP during contact tracing,³⁰ and in mid-2019, NC DIS began querying HIV-negative persons about PrEP awareness, interest, and current and past use. Pilot programs offering PrEP care or referrals out of select county health departments in NC are also underway,³¹ allowing assessment of these existing providers’ potential to reach underserved populations and address financial barriers to care. Although copay and medication assistance programs can reduce the cost of Truvada, these programs do not include provider care and laboratory tests,³² leaving a coverage gap that can be addressed by existing public health infrastructure.³³ NC DPH and other jurisdictions should consider offering same-day PrEP starts in partnership with county health departments during DIS interviews to support PrEP uptake within this population. Even if linkage to PrEP care is not immediately achieved, contact tracing and syphilis diagnoses offer opportunities to intervene on earlier stages of the HIV PrEP continuum,³⁴ including building PrEP awareness and support for PrEP use.

As demonstrated here, linkage of insurance claims and surveillance data offers a novel, useful approach to monitor and support PrEP use among key populations for HIV prevention. Surveillance data allowed identification of persons at high risk of HIV exposure within their sexual networks, and linkage to insurance claims data enabled assessment of PrEP use in this population. Linkage further allowed detection of erroneous ICD-9/10 CM codes for HIV diagnoses in persons receiving FTC/TDF, highlighting the value of triangulating multiple data sources to identify and correct misclassification.

Contact tracing data are subject to social desirability bias and recall error, preventing complete elucidation of the underlying network.³⁵ In addition, our analyses of DIS services and viral suppression may be subject to uncontrolled confounding by socioeconomic status, other life circumstances, and perceptions of public health services, which were unmeasured in our data source but could simultaneously affect both care-seeking behavior and being reached by DIS. Some persons reached by DIS might have achieved viral suppression even without intervention, and some not reached may have had challenging circumstances preventing both DIS contact and incident viral suppression. We also note that some persons without a viral load measure in the year before the network event may have received care in another state; however, this number is likely small because we excluded persons without a NC address at the network event. We were further unable to account for potential out-migration after a network event, potentially leading to underestimation of incident viral suppression. Despite mandatory viral load reporting to NC EDSS implemented in 2013, slow uptake by several providers delayed full statewide reporting until 2016 (Dr. Erika Samoff, NC DPH, personal communication 2020). Error may also have arisen from our assumption that all persons with unknown HIV status at the time of the network event were HIV-negative. However, HIV testing occurred in association with most network events and would have resulted in a recorded diagnosis if positive. Additionally, a sensitivity analysis requiring a negative HIV test in the three months before, at, or ever after the event showed only small increases in PrEP use estimates.

Insurance claims data provide estimates of medication dispensing but may not accurately reflect medication consumption. We also required only a single PrEP prescription claim for prevalent or incident PrEP use, preventing evaluation of long-term use. Observed PrEP use is generalizable only to network members with pharmacy coverage under a single private insurer in NC, a population which differs substantially from all HIV-negative network members. Estimates may also be reasonably generalizable to the remainder of the privately insured population. Although uninsured and publicly insured individuals are critical populations for HIV prevention efforts, PrEP use in these populations could not be assessed with available data. Data were also unavailable for persons who receive PrEP through Gilead’s patient assistance program and for insured enrollees under 18 years of age. We note, however, that in our population of persons with high HIV acquisition risk and access to PrEP under insurance coverage – a population in which PrEP use might be expected to approach an upper bound – we observed very little PrEP use overall. Recently added DIS interview questions on PrEP use and data on referrals for PrEP care may enable future analyses within the full population of HIV-negative contact network members. Future efforts to link surveillance data with Medicaid, Medicare, Gilead patient assistance program, and other insurance provider data may also improve generalizability.

In summary, although many HIV-negative members of the HIV/syphilis contact tracing network were indicated for PrEP, prevalent and incident PrEP use were low among commercially insured network members. Viral suppression among previously HIV-diagnosed persons in the network was also sub-optimal. Incident viral suppression among previously HIV-diagnosed, viremic network members was significantly lower among persons not reached by DIS, suggesting a need for increased support for DIS services in this population. These findings may inform expansion of health department PrEP services and guide efforts to increase viral suppression as jurisdictions across the US join the campaign to end HIV.³⁶