Contingency Management and SARS-CoV-2 Testing Among People Who Inject Drugs

Abstract

Objectives:

People who inject drugs (PWID) are especially vulnerable to morbidity and mortality as a result of SARS-CoV-2 infection because of social and physical health vulnerabilities. Routine testing for SARS-CoV-2 is critical to reduce transmission. Contingency management—the provision of tangible rewards to reinforce positive behavior—can promote the use of health services among PWID. Evidence is scarce on the utility of contingency management to promote SARS-CoV-2 testing. The objective of this study was to evaluate the effectiveness of contingency management to increase testing among PWID.

Methods:

SARS-CoV-2 testing was implemented at 9 syringe exchange program sites in partnership with an Oregon-based nonprofit organization for 5 weeks without contingency management and for 6 weeks with contingency management (a $10 financial incentive for testing) from February 1 through mid-April 2021. We measured rates of testing among syringe exchange program clients before and after implementation of contingency management.

Results:

Before contingency management, SARS-CoV-2 testing occurred during approximately 131 of 1410 (9.3%) client encounters, and 123 of 997 (12.3%) unique clients were tested. During contingency management, testing occurred during approximately 571 of 1756 (32.5%) client encounters, and 407 of 1151 (35.4%) unique clients were tested. Rates of testing increased from 0.04 (SD, 0.04) before contingency management implementation to 0.25 (SD, 0.15) after implementation (t₈ = −3.88; P = .005; Cohen d = 1.46).

Conclusions:

Contingency management facilitated uptake of SARS-CoV-2 testing among PWID. Contingency management may be an effective strategy for improving communicable disease testing beyond testing for SARS-CoV-2 and for improving vaccine uptake among PWID and warrants additional research.

Testing for the presence of SARS-CoV-2 decreased in the United States from January through July 2021 ¹ ; however, as COVID-19 resurged in July through September 2021, it was clear that testing was still an important strategy to mitigate its spread. First, vaccination rates were lower than needed to achieve herd immunity (estimated at 50%-70%).^2,3 Second, low vaccine accessibility and uptake likely contributed to rapid viral evolution and the emergence of new, more infectious SARS-CoV-2 variants. ⁴ In addition, the consequences of SARS-CoV-2 infection have become more severe for people experiencing homelessness as preventive public health measures and supportive resources have been discontinued in many communities; for example, temporary shelters have been discontinued, and sweeps of tent communities have displaced people who are unhoused.^5,6

Medically vulnerable populations who experience social disenfranchisement, such as people who inject drugs (PWID), are at greater risk than the overall population for experiencing COVID-19 complications. PWID have profound social challenges, such as homelessness, which lead to limited access to hygiene resources such as masks and handwashing stations to prevent transmission of SARS-CoV-2. They are also often likely to be living in congregate spaces such as shelters and prisons, where SARS-CoV-2 can spread rapidly.^7,8 PWID are also less likely than the general population to get a COVID-19 vaccine because of the stigma of drug use among health care providers; structural barriers to access to health care, including transportation and health insurance limitations; and vaccine hesitancy (Cioffi et al, unpublished data, 2021). Reasons for vaccine hesitancy include concerns about vaccine side effects, a lack of concern about getting COVID-19, not knowing enough about how the vaccine works, and general distrust of the vaccine development and deployment process (Cioffi et al, unpublished data, 2021). In addition, PWID experience poor disease outcomes as a result of underlying health conditions such as HIV, hepatitis C virus (HCV), ⁹ and other chronic medical conditions, such as cardiovascular diseases. ¹⁰

Syringe exchange programs (SEPs) are effective in reducing the transmission of blood-borne pathogens among PWID.^11-13 PWID view SEPs as accessible sites to receive high-quality, nonjudgmental medical care. ¹⁴ The Centers for Disease Control and Prevention cited SEPs as an “effective component of comprehensive community-based prevention and intervention,” and SEPs have been highlighted as an essential service during the pandemic.^14,15 Some SEPs provide access to services such as vaccination, testing, and linkage to care in addition to access to and disposal of syringes. ¹⁴ However, not all SEPs provide these additional resources, which leads to missed opportunities in health care.

Contingency management—the provision of tangible rewards to reinforce desired behaviors—has demonstrated success in promoting the use of health services among PWID. Among PWID, contingency management has improved HIV and HCV testing, hepatitis B vaccination rates,^16-21 and other health behaviors. However, limited evidence exists on the utility of contingency management to promote SARS-CoV-2 testing, an effective public health strategy for mitigating viral transmission and reducing COVID-19 morbidity and mortality. Thus, the objective of this study was to evaluate the effectiveness of contingency management at SEPs to increase SARS-CoV-2 testing among PWID. We hypothesized that contingency management in the form of a $10 financial incentive would increase testing among PWID.

Methods

Design, Setting, and Participants

This study was part of a larger effort funded by the National Institutes of Health, the Rapid Acceleration of Diagnostics for Underserved Populations (RADx-UP) initiative. As part of this study and in partnership with an Oregon-based nonprofit organization, HIV Alliance, we implemented a SARS-CoV-2 testing program at 9 SEPs in 4 counties (2 rural, 2 small urban) in Oregon. We used rural–urban commuting area (RUCA) codes to describe population density (rural vs urban) near each site. ²² HIV Alliance receives grants and private donations to provide syringe exchange services. It is the only organization that implements multiple SEPs throughout the state; other SEPs in the state are managed by public health departments. Syringe exchange occurs weekly at each syringe exchange location. This study was approved by the University of Oregon Institutional Review Board.

Although all participants in the testing program were SEP clients, our unit of analysis was SEP site, to reduce confounding caused by differences in site attendance. RADx-UP funding requirements included collecting data from all people tested. Although it was not our original intention to implement contingency management, to accomplish the goals of our funding agency, we implemented a $10 incentive in the form of a gift card (eg, Walmart) for completing a survey and SARS-CoV-2 test. We selected the amount of $10 to correspond with the time it takes to complete the survey and get tested and based on community partner feedback on the minimum amount that would incentivize SEP clients. On March 8, 2021, we introduced contingency management to our testing program approximately 5 weeks after initial implementation (on February 1, 2021) of the SARS-CoV-2 testing program. Testing outreach methods did not differ among sites. At each site, a pop-up tent with a large sign was present within about 50 feet of the tables for syringe exchange services. SEP staff members let clients know SARS-CoV-2 testing was available and also let clients know when the $10 gift cards became available. Once gift cards became available, clients were quick to let other clients know. Every SEP client who received a SARS-CoV-2 test also completed a survey. Completing a survey was the condition of getting the gift card; for this reason, no clients, to our knowledge, opted out of the survey. The survey was administered by HIV Alliance staff who received training from the study team on human subjects research and signed individual investigator agreements, as permitted by the University of Oregon Institutional Review Board. Data collection occurred from the beginning of February through mid-April 2021.

Main Outcome and Measures

The main outcome variable was the proportion of SEP clients per event who were tested for SARS-CoV-2. To compute this proportion, we divided the number of SEP clients who participated in testing (numerator) at each event by the number of SEP clients who participated in each exchange (denominator) at each event. Participation at an event is considered a client encounter. We averaged proportions across days (2-14 days) within each site (N = 9) before contingency management implementation (approximately 5 weeks) and after contingency management implementation (approximately 6 weeks), resulting in 2 data points for each of the 9 sites: before contingency management and during contingency management.

We determined the number of SEP clients who engaged in SARS-CoV-2 testing by asking clients whether they were SEP clients at the time of testing. These were important data to ensure that we included only SEP clients in our analyses. Two SEPs were co-located at day-use centers for unhoused people; thus, people who were not SEP clients also used SARS-CoV-2 testing services.

We collected data on the number of SEP clients who participated in each exchange from HIV Alliance; the organization provided information on the number of SEP clients who engaged in SEP services.

Analysis Plan

We collected data on the proportion of SEP clients who tested for SARS-CoV-2 per week before and after implementation of contingency management (during contingency management). We aggregated and analyzed these data by phase and site using paired t tests to examine contingency management effects on SARS-CoV-2 testing rates. We calculated the Cohen d as a measure of effect size; values of 0.2, 0.5, and 0.8 correspond to small, medium, and large effects, respectively. ²³ We considered alternative approaches such as a multilevel model to examine the proportion of variance in testing rates between (vs within) sites; however, with only 9 sites, this approach may have led to bias in results, such as inflated type I error rates and inadmissible solutions.^24,25 Finally, we estimated the annual costs of implementing contingency management for urban and rural counties. These estimates did not account for factors such as staff time to procure, organize, administer, and track incentives.

Results

The number of encounters and unique clients who participated in syringe exchange and testing before contingency management and during contingency management roughly mirrored the general SEP client population: approximately 80% White, 10% Hispanic/Latino, 30% female, and 55% temporarily housed or unhoused (Table 1).

Table 1.

Demographic characteristics of all SEP clients and for the subset of SEP clients who participated in SARS-CoV-2 testing before and during contingency management, Oregon, February–April 2021 ^a

Characteristic	Pre–contingency management		During contingency management
	All SEP clients	Tested for SARS-CoV-2	All SEP clients	Tested for SARS-CoV-2
Total no. of encounters	1410	131	1756	571
No. of unique clients	997	123	1151	407
Temporarily housed or unhoused	544 (55)	53 (43)	671 (58)	261 (64)
Race
American Indian/Alaska Native	45 (5)	4 (3)	48 (4)	18 (4)
Asian	6 (1)	2 (2)	5 (0)	2 (0)
Black/African American	23 (2)	0	29 (3)	10 (2)
Multiracial	57 (6)	12 (10)	63 (5)	40 (10)
Native Hawaiian/Other Pacific Islander	8 (1)	0	11 (1)	2 (0)
White	822 (82)	103 (84)	955 (83)	323 (79)
Declined to answer	36 (4)	2 (2)	40 (3)	12 (3)
Ethnicity
Hispanic/Latino	57 (6)	15 (12)	68 (6)	35 (9)
Non-Hispanic/Latino	970 (87)	108 (88)	1008 (88)	371 (91)
Declined to answer	70 (7)	0	75 (7)	1 (0)
Sex/gender
Female	347 (35)	32 (26)	394 (34)	133 (33)
Male	614 (62)	89 (72)	712 (62)	266 (65)
Female-to-male transgender	2 (0)	0	4 (0)	1 (0)
Male-to-female transgender	3 (0)	0	1 (0)	0
Nonbinary	2 (0)	0	3 (0)	2 (0)
Other	9 (1)	1 (1)	18 (2)	1 (0)
Declined to answer	20 (2)	1 (1)	19 (2)	4 (1)

Abbreviation: SEP, syringe exchange program.

^aA SARS-CoV-2 testing program was implemented at 9 SEPs in Oregon. Contingency management is the provision of tangible rewards to reinforce positive behavior; all SEP clients who completed a survey and got tested were given a $10 gift card. All values are number (percentage) unless otherwise indicated. Percentages may not total to 100 because of rounding.

We found substantial differences among sites in the utility of contingency management. Specifically, in less population-dense areas, contingency management did not improve SARS-CoV-2 testing among PWID (Table 2). The average SARS-CoV-2 testing rates across the study period increased sharply during contingency management (Figure 1). Rates increased significantly from 0.04 (SD, 0.04) before implementation to 0.25 (SD, 0.15) after implementation (t₈ = −3.88; P = .005; Cohen d = 1.46; Figure 2).

Table 2.

Site characteristics and intervention effects of a SARS-CoV-2 testing program at 9 SEP sites before and during implementation of contingency management, Oregon, February–April 2021 ^a

Site	Pre–contingency management, % (numerator/denominator) b	During contingency management, % (numerator/denominator) b	Location c	Rural–urban commuting area code d
Site A	2 (1/61)	44 (49/111)	Clinic	1
Site B	8 (15/196)	38 (58/154)	Office	1
Site C	1 (1/78)	29 (20/70)	Mobile	1
Site D	6 (2/31)	28 (19/68)	Day-use shelter	1
Site E	0 (0/83)	24 (55/228)	Mobile	1
Site F	3 (7/232)	21 (68/323)	Day-use shelter	1
Site G	11 (13/117)	12 (31/254)	Office	4
Site H	0 (0/47)	8 (8/102)	Church	1
Site I	3 (1/34)	2 (1/59)	Church	10

Abbreviation: SEP, syringe exchange program.

^aA SARS-CoV-2 testing program was implemented at 9 SEPs in Oregon. Contingency management is the provision of tangible rewards to reinforce positive behavior; all SEP clients who completed a survey and got tested were given a $10 gift card. All values are number (percentage) unless otherwise indicated.

^bThe numerator was the number of SEP clients who participated in SARS-CoV-2 testing, and the denominator was the number of SEP clients who participated in an exchange at each event.

^cAll testing events were held outside under a pop-up tent, regardless of location type.

^d1 = Metropolitan area core, primary flow within an urbanized area; 4 = micropolitan area core, primary flow within an urban cluster of 10 000-49 999; 10 = rural area, primary flow to a tract outside an urbanized areas or urban cluster. ²²

Figure 1.

SARS-CoV-2 testing rates, by week, among clients at 9 syringe exchange program locations in Oregon, February–April 2021, before and after implementation of contingency management. Contingency management is the provision of tangible rewards to reinforce positive behavior; all clients who completed a survey and got tested were given a $10 gift card. The vertical dashed line indicates implementation of contingency management on March 8, 2021. Error bars indicate SDs.

Figure 2.

Summary statistics for SARS-CoV-2 testing rates among clients at 9 syringe exchange program locations in Oregon, February–April 2021, before and after implementation of contingency management. Contingency management is the provision of tangible rewards to reinforce positive behavior; all clients who completed a survey and got tested were given a $10 gift card. The horizontal line inside the boxes indicates the median; the x indicates the mean, and the lower and upper ends of the boxes are the first and third quartiles. The whiskers indicate the upper and lower range of values.

Across 9 sites, approximately 1.0 (SD, 1.3; median = 0.3 [IQR, 0.3-1.4]) SEP client was tested per week at each site (a total of 9 clients per week) before implementation of contingency management. After implementation, approximately 6.0 (SD, 4.2; median = 5.2 [IQR, 3.2-9.2]) SEP clients were tested per week at each site (a total of 54 clients per week), corresponding to an average cost of approximately $540 per week or $28 080 per year (based on a $10 incentive per client).

Per county, the annual cost of implementing a contingency management program (based on a $10 incentive) would range from approximately $1040 for rural counties (2 clients × $10 × 1 site × 52 weeks) to approximately $15 600 for more urban counties (10 clients × $10 × 3 sites × 52 weeks). For larger counties, when SEPs are nested at day-use centers for unhoused clients, the weekly number would increase by approximately 25 clients and increase the annual cost to $28 600 ([(10 clients × $10 × 3 sites) + (25 clients × $10 × 1 site)] × 52 weeks).

Discussion

We initiated a SARS-CoV-2 testing program among PWID at 9 SEPs in Oregon. Approximately 5 weeks after implementation of the testing program, we began offering contingency management (a $10 financial incentive) to SEP clients to encourage them to take a brief survey and participate in testing. We compared testing rates before and after implementation of contingency management and found that contingency management significantly and meaningfully increased testing among PWID participating in syringe exchange. Thus, we found that testing for SARS-CoV-2 at SEPs is an effective strategy for facilitating access to testing among PWID.

Although contingency management has been studied in various contexts related to PWID, no studies, to our knowledge, have been conducted on the effectiveness of contingency management for SARS-CoV-2 testing among PWID. There is a need to continue testing among PWID given their increased vulnerability to COVID-19, their lower-than-average access to and uptake of vaccination, and new SARS-CoV-2 variants that may decrease vaccine efficacy and lead to resurgence in disease. Studies on contingency management as it relates to testing for other infectious diseases among PWID have been limited to hepatitis B virus,^20,26 HCV,^16,27 tuberculosis, ²⁸ HIV,^29-31 and treatment for drug and alcohol use disorders. ³² Offering contingency management for testing may increase detection of conditions requiring intervention, such as sexually transmitted infections, cancer, diabetes, pregnancy, and other conditions (ie, HIV, HCV, and tuberculosis). With appropriate follow-up, testing may lead to reduced transmission of infectious diseases and improved treatment. These are important services to embed into SEPs; many SEPs do not consistently provide access to testing, and most do not provide comprehensive follow-up care. Contingency management may also be a way to improve vaccine uptake and adherence among PWID for COVID-19 and other infectious diseases. However, incentives may encourage people to obtain vaccines when they have already received them. To mitigate this challenge, providing financial incentives for vaccination should be paired with comprehensive monitoring systems to ensure people are not engaging in contraindicated health behaviors (eg, overvaccination).

Finally, the benefits of SARS-CoV-2 testing if appropriate follow-up occurs cannot be understated: the cost of an inpatient stay for people admitted for COVID-19 has been estimated at approximately $14 000 per patient. ³³

Limitations

Our study had at least 2 potential limitations. First, the main limitation of this study was the pre–post design, which may have introduced historical confounding in either direction. It may have taken time for clients to gain trust in the testing program; thus, testing rates may have naturally increased over time rather than as a result of contingency management. However, contingency management was implemented when SARS-CoV-2 testing rates were decreasing in the United States, so we should have seen decreases rather than increases in testing among PWID. Thus, the effects of contingency management in our study may have been smaller than the effects that would have been obtained in a randomized controlled trial. Second, we analyzed rates of testing among sites, rather than among individual clients, because of limitations in available data.

Conclusions

Contingency management—offering financial incentives for participation in testing—is an effective strategy for increasing rates of SAR-CoV-2 testing among PWID. To maintain SARS-CoV-2 testing rates, financial incentives should continue to be offered. In addition, an opportunity exists to improve the uptake of testing and vaccination for a multitude of infectious diseases by offering both testing and vaccination services in a single SEP location and by providing financial incentives to improve uptake. This study demonstrates that providing services on site and providing financial incentives are both feasible and useful.