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People who inject drugs may be at elevated SARS-CoV-2 risk due to their living conditions and/or exposures when seeking or using drugs. No study to date has reported upon risk factors for SARS-CoV-2 infection among people who inject drugs. Between October, 2020 and June, 2021, participants aged ≥18 years from San Diego, California, USA and Tijuana, Baja California, Mexico who injected drugs within the last month underwent interviews and testing for SARS-CoV-2 RNA and antibodies. Binomial regressions identified correlates of SARS-CoV-2 seropositivity. Of 386 participants, SARS-CoV-2 seroprevalence was 36.3% (95% CI: 31.5%-41.1%); 92.1% had detectable IgM antibodies. Only 37.5% had previously been tested. Seroprevalence did not differ by country of residence. None tested RNA-positive. Most (89.5%) reported engaging in ≥1 protective behavior [e.g., facemasks (73.5%), social distancing (46.5%), or increasing handwashing/sanitizers (22.8%)]. In a multivariate model controlling for sex, older age, and Hispanic/Latinx/Mexican ethnicity were independently associated with SARS-CoV-2 seropositivity, as was engaging in sex work (AdjRR: 1.63; 95% CI: 1.18-2.27) and having been incarcerated in the past six months (AdjRR: 1.49; 95% CI: 0.97-2.27). Comorbidities and substance using behaviors were not associated with SARS-CoV-2 seropositivity. In this community-based study of people who inject drugs in the San Diego-Tijuana border region, over one third were SARS-CoV-2 seropositive, exceeding estimates from the general population in either city. We found no evidence that substance use behaviors were associated with an elevated risk of SARS-CoV-2 infection, but observed that circumstances in the risk environment, notably sex work and incarceration, were independently associated with higher SARS-CoV-2 seroprevalence. Our findings suggest that a binational policy response to COVID-19 mitigation is warranted beyond the closure of the U.S.-Mexico border. Furthermore, decriminalizing sex work and drug use could reduce the burden of COVID-19 among people who inject drugs.

Domains of adequate menstrual health (MH) include access to water, sanitation, and hygiene (WASH). People who menstruate with social disadvantages-such as homelessness or drug injection practices-often face barriers to WASH access. However, validated instruments to measure MH are limited among marginalized populations, and available instruments involve lengthy surveys. We developed and evaluated psychometric properties of a novel 'MH WASH Domain Scale-12' among people who menstruate and who inject drugs in the Tijuana-San Diego region and identified correlates of MH access using this scale. We constructed a MH-scale based on access to twelve WASH-related items: (1) menstrual products, (2) body hygiene (bathing per week), (3) water sources for bathing, (4) improved, (5) non-shared, (6) available, (7) private, (8) nearby, (9) and safe sanitation facilities, (10) availability of soap, (11) water source for handwashing, and (12) handwashing facilities with soap/water. Variables were dichotomized and summed, with scores ranging from 0-12 points and higher scores indicating better MH access. We assessed the scale's reliability and construct and content validity using data from a binational cross-sectional study. The sample included people who inject drugs (PWID) who had ever menstruated in their lifetime and were 18+ during 2020-2021. MH-WASH items were described, and the scale was further used as an outcome variable to identify correlates. Among 125 (124 cis-female and 1 trans-male) PWID that reported menstruating, our 'MH WASH Domain Scale-12' was reliable (Cronbach's alpha = 0.81, McDonald's Omega total = 0.83) and valid. We identified two sub-domains: Factor-1 included items describing 'WASH availability' and Factor-2 contained items related to 'WASH security'-encompassing physical and biological safety. Scale scores were significantly lower among participants experiencing unsheltered homelessness compared to participants experiencing sheltered homelessness or living in permanent housing. We constructed and validated a novel and reliable scale to measure MH-related WASH access that can be used to assess MH among marginalized populations in English- and Spanish-speaking contexts. Using this scale we identified disparities in MH-WASH access among PWID and who menstruate in the US-Mexico border region.

Background The unpredictable and toxic nature of the unregulated drug supply poses overdose and other health risks for people who use drugs (PWUD). Drug checking services can reduce risks by identifying adulterants in individuals’ drug supplies. In the United States (U.S.), DCS are increasingly offered through community harm reduction services that provide evidence-based risk reduction services for PWUD, such as syringe services programs (SSPs). However, PWUD face several multi-level barriers to consistently utilizing DCS and engaging in post-DCS safer drug use behaviors (e.g., discard, use less, avoid using alone, etc.). Staff from a San Diego-based mobile SSP and researchers drew from Social Cognitive Theory and the Social Ecological Model to develop a motivational-interviewing adjunctive intervention (MI-CHANCE) led by peers with lived substance use experience to address multi-level barriers and promote DCS engagement and adoption of post-DCS safer drug use behaviors among PWUD. Methods We employ a hybrid type-1 effectiveness–implementation trial with a primary goal of determining effectiveness of the MI-CHANCE adjunctive intervention in increasing DCS utilization (primary behavioral outcome) and safer drug use behaviors (secondary behavioral outcome), leading to reduced overdose risk (primary health outcome) and HIV/HCV incidence (secondary health outcome). We will recruit, consent, conduct a baseline interview, and randomize 588 PWUD who used opioids or stimulants within the week prior to receive either MI-CHANCE or an attention-control standard-of-care condition. All participants will be offered DCS following exposure to the intervention or control condition. We will conduct six-month follow-up with participants over a 30-month period to collect outcomes and hypothesized predictors, mediators and potential confounders. Our secondary goal is to assess MI-CHANCE implementation considerations guided by the RE-AIM/PRISM framework via annual in-depth interviews over the course of the trial with SSP staff ( N  = 5) and participants ( N  = 20), focusing on acceptability and feasibility, and the potential for scalability via interviews with a broad sample of diverse U.S. SSPs ( N  = 20). Discussion This hybrid trial will advance crucial knowledge on the effectiveness and implementation of an adjunctive intervention to promote DCS engagement and safer drug use behaviors to reduce overdose risk among PWUD. Trial registration ClinicalTrials.gov, NCT06855836. Registered February 28, 2025. https://clinicaltrials.gov/study/NCT06855836?term=NCT06855836/rank=1 .

Background Water, sanitation, and hygiene (WaSH) insecurity increases the risk of water-related diseases. However, limited research has been conducted on psychosocial distress as it relates to WaSH insecurity, especially among people who inject drugs (PWID). We examined the relationship between WaSH insecurity and related anxiety among PWID living in different housing conditions along the US-Mexico border region. Methods From 2020–2021, a cross-sectional study was conducted among 585 people who injected drugs within the last month in Tijuana ( N  = 202), San Diego ( N  = 182), and in both Tijuana and San Diego ( N  = 201). Participants underwent interviewer-administered surveys related to WaSH access, substance use, and generalized anxiety disorder (GAD-7). Quasi-Poisson regressions were used to assess associations between WaSH insecurity and anxiety in the prior 6-months. Results Participants were 75% male, 42% were unhoused and 91% experienced WaSH insecurity in the prior 6-months. After adjusting for housing status, gender, and age, lack of access to basic drinking water (Adj RR: 1.28; 95% CI: 1.02–1.58), sanitation (Adj RR:1.28; 95% CI: 1.07–1.55), and a daily bath/shower (Adj RR: 1.38; 95% CI: 1.15–1.66) were associated with mild-severe anxiety. The number of WaSH insecurities was independently associated with a 20% increased risk of experiencing anxiety per every additional insecurity experienced (Adj RR: 1.20; CI: 1.12–1.27). We also found a significant interaction between gender and housing status ( p  = 0.003), indicating that among people experiencing sheltered/unsheltered homelessness, women had a higher risk of mild-severe anxiety compared to men (Adj RR: 1.55; 95% CI: 1.27–1.89). At the same time, among women, those who are unhoused have 37% increased risk of anxiety than those who live in stable housing conditions (Adj RR: 1.37; 95% CI: 1.01–1.89). Conclusion The lack of specific WaSH services, particularly lack of drinking water, toilets, and daily showers were associated with higher levels of anxiety among PWID in the Tijuana-San Diego border region. Women experiencing homelessness were especially vulnerable. WaSH interventions that provide safe, 24-h access may help to reduce anxiety and health risks associated with WaSH insecurity.

Background People who inject drugs (PWID) are vulnerable to SARS-CoV-2 infection. We examined correlates of COVID-19 testing among PWID in the U.S.-Mexico border region and described encounters with services representing potential opportunities (i.e., ‘touchpoints’) where COVID-19 testing could have been offered. Methods Between October, 2020 and September, 2021, participants aged ≥18 years from San Diego, California, USA and Tijuana, Baja California, Mexico who injected drugs within the last month completed surveys and SARS-CoV-2, HIV, and HCV serologic testing. Logistic regression identified factors associated with COVID-19 testing including potential touchpoints, comorbidities and COVID-19 related misinformation and disinformation. Results Of 583 PWID, 30.5% previously had a COVID-19 test. Of 172 PWID who tested SARS-CoV-2 seropositive (30.1%), 50.3% encountered at least one touchpoint where COVID-19 testing could have been offered within the prior six months. Factors independently associated with at least two fold higher odds of COVID-19 testing were living in San Diego, recent incarceration, receiving substance use treatment, and experiencing ≥1 chronic health condition. Homelessness, having received ≥1 dose of COVID-19 vaccine, and having a HIV or HCV test since the COVID-19 epidemic began were also independently associated with having had a prior COVID-19 test. Conclusion We identified several factors independently associated with COVID-19 testing and multiple touchpoints where COVID-19 testing could be scaled up for PWID, such as SUD treatment programs and syringe service programs. Integrated health services are needed to improve access to rapid, free COVID-19 testing in this vulnerable population.

Background HIV self-testing (HIVST) could increase HIV testing access among people who inject drugs (PWID), and secondary distribution (i.e., peer-delivery) of HIVST kits in PWID social networks could further expand coverage. We assessed willingness to use and distribute HIVST kits among PWID in the San Diego–Tijuana border region. Methods From 2020 to 2021, HIV-negative PWID in San Diego, USA, and Tijuana, Mexico, completed surveys and provided data on individual ( N  = 539) and social network ( N  = 366) characteristics. We used modified Poisson regression to examine the effects of individual and social network characteristics on willingness to use and distribute HIVST kits. Results Most participants were willing to use (81%) and distribute (81%) HIVST kits. At the individual level, prior HIV testing was positively associated with willingness to use (adjusted prevalence ratio [aPR] = 1.24, 95% confidence interval [CI] 1.10–1.40) and distribute (aPR = 1.27, 95% CI 1.12–1.43) HIVST kits, while perceiving oneself to be at higher HIV risk than others was negatively associated with willingness to use HIVST kits (aPR = 0.83, 95% CI 0.74–0.93). At the network level, willingness to distribute HIVST kits was positively associated with network size (aPR = 1.04 per member, 95% CI 1.01–1.08) and greater proportions of one’s network encouraging them to use drugs (aPR = 1.29, 95% CI 1.16–1.44) and having a history of homelessness (aPR = 1.51, 95% CI 1.31–1.74) or detention/arrest (aPR = 1.57, 95% CI 1.36–1.82), and negatively associated with a greater proportion of one’s network including “very close” persons (aPR = 0.80, 95% CI 0.69–0.94). Conclusions We found high potential for HIVST kits and their secondary distribution to increase HIV testing among PWID who face the greatest barriers to facility-based testing.

Background Pre-exposure prophylaxis (PrEP) holds promise for decreasing new HIV infections among people who inject drugs (PWID), yet daily oral PrEP use is low, and PrEP modality and delivery strategy preferences in this population remain understudied. Methods From May 2022-June 2023, we conducted a discrete choice experiment (DCE) with PWID in San Diego, California. Participants viewed 18 PrEP program scenarios in sets of three and chose their preferred scenario within each set. Scenarios consisted of various combinations of five characteristics: PrEP modality (injectable, implantable, oral), frequency of use (annual, bi-monthly, daily), service location (community-based organization, clinic, telemedicine), prescription access location (on-site, street outreach, mail), and adherence supports (social support, outreach worker, phone/text reminder). Multinomial logit regression estimated probabilities of choosing PrEP program scenarios as a function of the five characteristics to estimate part-worth utility scores (PWUS; reflecting relative preferences for specific characteristic values) and relative importance scores (RIS; reflecting the relative influence of each characteristic on program choice). We also explored differences by hypothesized modifiers of preferences (i.e., sex assigned at birth, housing status, injection frequency, prior PrEP awareness). Results Among 262 participants, mean age was 43.1 years, and most reported male sex assigned at birth (69.5%), identified as non-Hispanic (60.3%), and were previously unaware of PrEP (75.2%). Frequency of use (RIS: 51.5) and PrEP modality (RIS: 35.3) had the greatest influence on PrEP program choice. Within these characteristics, participants had relative preferences for annual use (PWUS: 0.83) and oral PrEP (PWUS: 0.57), and relative aversions to daily use (PWUS: -0.76) and implantable PrEP (PWUS: -0.53). Generally, participants did not indicate preferences for specific service or prescription access locations, or adherence supports; however, among those with prior PrEP awareness, prescription access location and adherence supports had a slightly greater influence on PrEP program choices. Conclusion Our study considered diverse PrEP scenarios and highlighted potential preferences for long-acting oral modalities. Although not currently available, renewed investment in long-acting oral PrEP formulations may facilitate PrEP care engagement among PWID. Additional delivery and implementation strategy research is needed to support PrEP uptake and persistence in this population.

Background People who inject drugs (PWID) have low rates of COVID-19 testing and vaccination and are vulnerable to severe disease. We partnered with a local, community-based syringe service program (SSP) in San Diego County, CA, to develop the single-session theory- and evidence-informed “LinkUP” intervention to increase COVID-19 testing and vaccination. This paper details the protocol for a pilot randomized controlled trial (RCT) of the LinkUP intervention. Methods With significant community input into study design considerations, including through our Community and Scientific Advisory Board, the LinkUP pilot RCT leverages an ongoing cohort study with adult (≥ 18 years) PWID in San Diego County to recruit participants who have not recently undergone voluntary COVID-19 testing and are unvaccinated. Eligible participants are referred to SSP locations randomized to offer the active intervention (involving tailored education, motivational interviewing, and problem-solving strategies) or a didactic attention-control condition (information sharing only). Both conditions are delivered by trained peer counselors hired by the SSP and were designed to be delivered at mobile (outdoor) SSP sites in ~ 30 min. Intake data assesses COVID-19 testing and vaccination history, health status, and harm reduction needs (to facilitate SSP referrals). At the end of either intervention condition, peer counselors offer onsite rapid COVID-19 antigen testing and COVID-19 vaccination referrals. Out-take and follow-up data (via SSP and state health department record linkages) confirms whether participants received the intervention, COVID-19 testing (and results) onsite or within six months, and vaccination referrals (and uptake) within six months. Planned analyses, which are not powered to assess efficacy, will provide adequate precision for effect size estimates for primary (COVID-19 testing) and secondary (vaccination) intervention outcomes. Findings will be disseminated widely including to local health authorities, collaborating agencies, and community members. Discussion Lessons from this community-based pilot study include the importance of gathering community input into study design, cultivating research-community partnerships based on mutual respect and trust, and maintaining frequent communication regarding unexpected events (e.g., police sweeps, neighborhood opposition). Findings may support the adoption of COVID-19 testing and vaccination initiatives implemented through SSPs and other community-based organizations serving vulnerable populations of people impacted by substance use and addiction. Trial registration This trial was registered prospectively at ClinicalTrials.gov (identifier NCT05181657).

Background People who use drugs (PWUD) experience elevated HIV risk and numerous barriers to facility-based HIV testing. HIV self-testing (HIVST) could circumvent many of those barriers and is acceptable among PWUD, yet HIVST implementation for PWUD is limited. Service providers’ perspectives on specific HIVST delivery strategies could help increase availability for PWUD. Methods From April–November 2021, we interviewed 16 health, harm reduction, and social service providers working with PWUD in San Diego, CA. Interviews and rapid thematic analysis explored perspectives on HIVST’s utility and appropriateness, as well as the feasibility of and anticipated challenges with specific HIVST delivery strategies, including peer or secondary distribution. Results Participants viewed HIV as a significant threat to PWUD health and confirmed the presence of numerous barriers to local facility-based HIV testing. Participants viewed HIVST as a promising and potentially empowering solution. Based on community familiarity with secondary distribution of harm reduction supplies (i.e., naloxone) and information, participants viewed secondary distribution of HIVST kits as an appropriate and feasible strategy for increasing the reach of HIVST, but also described potential barriers (e.g., engaging socially disconnected individuals, ensuring linkages to services following HIVST) and provided suggestions for alternative HIVST kit delivery models (e.g., harm reduction vending machines). Conclusions Service providers viewed secondary distribution of HIVST kits among PWUD as promising, appropriate, and feasible, yet specialized efforts may be needed to reach the most marginalized individuals and ensure consistent provision of educational information and referral supports that maximize the impact of this approach.

Background Water, sanitation, and hygiene (WASH) access is critical to public health and human dignity. People who inject drugs (PWID) experience stigma and structural violence that may limit WASH access. Few studies have assessed WASH access, insecurity, and inequities among PWID. We describe WASH access, social and geographic inequalities, and factors associated with WASH insecurity among PWID in the Tijuana-San Diego metropolitan area. Methods In this cross-sectional binational study, we interviewed PWID (age 18+) in 2020–2021 about WASH access and insecurity. City of residence (Tijuana/San Diego) and housing status were considered as independent variables to describe key WASH access outcomes and to assess as factors associated with WASH insecurity outcomes. Measures of association between outcomes and independent variables were assessed using log modified-Poisson regression models adjusting for covariates. Results Of 586 PWID (202 Tijuana; 384 San Diego), 89% reported basic access to drinking water, 38% had basic hand hygiene, 28% basic sanitation, and 46% access to bathing, and 38% reported recent open defecation. Participants residing in Tijuana reported significantly higher insecurity in accessing basic drinking water (aRR: 1.68, 95%CI: 1.02–2.76), basic hygiene (aRR: 1.45, 95%CI: 1.28–1.64), and bathing (aRR: 1.21, 95%CI: 1.06–1.39) than those living in San Diego. Participants experiencing unsheltered homelessness experienced significantly higher insecurity in accessing basic drinking water (aRR: 2.03, 95%CI: 1.07–3.86), basic sanitation (aRR: 1.68, 95%CI: 1.48, 1.92), bathing (aRR: 1.84, 95%CI: 1.52–2.22), and improved water sources for cleaning wounds (aRR: 3.12, 95%CI: 1.55–6.29) and for preparing drugs (aRR: 2.58, 95%CI: 1.36–4.89) than participants living in permanent housing. Conclusion WASH access among PWID in the Tijuana-San Diego metropolitan area was low by international standards and lower than the national averages in both countries. Homelessness was significantly associated with WASH insecurity in this population. Concentrated efforts are needed to guarantee continuously available WASH services for PWID—especially those who are unsheltered.