Adult immunization coverage remains low in the US, particularly for people who use drugs (PWUD), a population that experiences a disproportionate burden of vaccine-preventable diseases. The extent of and characteristics associated with vaccine confidence (VC) held by PWUD is poorly understood. As VC strongly correlates with vaccine uptake, this cross-sectional study identifies mutable factors associated with VC and quantifies its relationship to immunization status within a highly vulnerable, underimmunized population of PWUD. Using a community-engaged research strategy with select partner organizations hosting syringe exchange programs in Atlanta, Los Angeles, and Las Vegas, USA, we surveyed participants ages 18-69 years served by these organizations from 2019 to 2020. Survey measures included sociodemographics, health behavior including immunization receipt, and vaccine confidence in adult vaccinations using a modified Emory Vaccine Confidence Index (EVCI). The findings reflect relatively low VC among the 1,127 recruited participants, with 56% expressing low VC (EVCI 0-12), 35% medium (EVCI 13-20) and 10% high (EVCI 21-24). EVCI varied by city, with lowest confidence in Atlanta and highest in Las Vegas. VC was associated with past receipt of specific vaccines, including hepatitis A, MMR, Tdap, and influenza. VC varied by specific sociodemographic correlates such as housing insecurity (reduced confidence) and receipt of public benefits or disability (increased confidence). This study identified correlates associated with VC based on site and sociodemographic characteristics for this priority population, highlighting the need for specific interventions to raise VC among PWUD, especially among those experiencing housing insecurity and without public benefits.
Keywords: Vaccine confidence; cross-sectional survey; hidden populations; people who use drugs; population survey; vaccine access; vaccine attitudes; vaccine equity; vaccine trust; vulnerable populations.