Illicit Fentanyl Use and Hepatitis C Virus Seroconversion Among People Who Inject Drugs in Tijuana and San Diego: Results From a Binational Cohort Study.

BACKGROUND: Illicitly manufactured fentanyl (IMF) increases overdose mortality, but its role in infectious disease transmission is unknown. We examined whether IMF use predicts hepatitis C virus (HCV) and human immunodeficiency virus (HIV) incidence among a cohort of people who inject drugs (PWID) in San Diego, California and Tijuana, Mexico. METHODS: PWID were recruited during 2020-2022, undergoing semi-annual interviewer-administered surveys and HIV and HCV serological rapid tests through 2024. Cox regression was conducted to examine predictors of seroconversion considering self-reported IMF use as a 6-month lagged, time-dependent covariate. RESULTS: Of 398 PWID at baseline, 67% resided in San Diego, 70% were male, median age was 43 years, 42% reported receptive needle sharing, and 25% reported using IMF. HCV incidence was 14.26 per 100 person-years (95% confidence interval [CI]: 11.49-17.02), and HIV incidence was 1.29 (95% CI: .49-2.10). IMF was associated with HCV seroconversion, with a univariable hazard ratio (HR) of 1.64 (95% CI: 1.09-2.40), and multivariable HR of 1.57 (95% CI: 1.03-2.40). The direction of the relationship with HIV was similar, albeit not significant (HR 2.39; 95% CI: .66-8.64). CONCLUSIONS: We document a novel association between IMF and HCV seroconversion among PWID in Tijuana-San Diego. Few HIV seroconversions (n = 10) precluded our ability to assess if a similar relationship held for HIV. IMF's short half-life may destabilize PWID-increasing the need for repeat dosing and sharing smoking materials and syringes. New preventive care approaches may reduce HCV transmission in the fentanyl era.

COVID-19 vaccine uptake among people who inject drugs in Tijuana Mexico.

Background: SARS-CoV-2 prevalence is elevated among people who inject drugs (PWID). In Tijuana, Mexico, COVID-19 vaccines became available to the general population in June 2021, but uptake among PWID was <10%. We studied COVID-19 vaccine uptake among PWID in Tijuana following implementation of a pop-up vaccination clinic. Methods: Beginning in October, 2020, PWID in Tijuana aged ≥18 years were enrolled into a longitudinal cohort study. At baseline and semi-annually, participants underwent interviewer-administered interviews on health behaviors and COVID-19 exposures through April 5, 2022. From June 21-September 20, 2021, staff referred PWID to a temporary COVID-19 vaccine pop-up clinic that was coincidentally established near the study office. Participants attending the clinic completed a short interview on barriers to vaccination and were offered facilitated access to free Janssen® COVID-19 vaccine. All participants were reimbursed $5 for this interview, regardless of whether or not they chose to be vaccinated. Poisson regression was used to evaluate the effect of the pop-up clinic on COVID-19 vaccination uptake, controlling forpotential confounders. Results: Of 344 participants, 136 (39.5%) reported having received at least one COVID-19 vaccine dose during the 10 months follow-up period, of whom 113 (83.1%) received vaccine at the pop-up clinic and 23 (16.9%) elsewhere. One third of those receiving COVID-19 vaccine during the pop-up clinic were previously vaccine hesitant. Attending the pop-up clinic was independently associated with higher rates of COVID-19 vaccination Adjusted Rate Ratio (AdjRR: 9.15; 95% CI: 5.68-14.74). Conclusions: We observed a significant increase in COVID-19 vaccine uptake associated with attending a temporary pop-up vaccine clinic in Tijuana suggesting that efforts to improve vaccination in this vulnerable population should include convenient locations and staff who have experience working with substance using populations. Since COVID-19 vaccination rates remain sub-optimal, sustained interventions to increase uptake are needed.