Prevalence and factors associated with neck injection among people who inject drugs in San Francisco, California

Background: Groin and neck injections are generally a last resort for people who inject drugs (PWID) who do not have easy access to functioning veins. These alternative injection practices can lead to an increased likelihood of adverse health outcomes. There is still much we do not know about groin and neck injections among PWID in the US, as the literature to-date comes from studies primarily focused on groin injections outside the US. We assessed prevalence, predictors, and associated behaviors of neck injection through a survey fielded in San Francisco, California, US.Methods: The sample comes from a longitudinal observational study that used targeted sampling to recruit PWID in San Francisco. The current study sample includes 239 PWID who completed their 12-month survey between June 2019 and June 2020.Results: About a third of the sample reported injecting in their neck in the past 30 days, with the most common reason being lack of available veins. Age, past 6-month abscess / soft tissue infection, and past 30-day use of opioids mixed with cocaine were significantly associated with past 30-day neck injection in the final multivariate model. Past 30-day neck injection was also significantly associated with being injected by another person in the past 30 days.Conclusions: PWID at higher risk for vein deterioration were more likely to inject into their neck. Harm reduction strategies such as safer injection counseling, safe smoking supplies, use of "street doctors," and safe consumption sites may reduce instances of neck injection and/or associated health risks.