People who inject drugs (PWID) face an increased risk of certain infectious diseases, including vaccine-preventable diseases such as hepatitis A, hepatitis B, tetanus, and pneumococcal pneumonia (Centers for Disease Control and Prevention, 1998; Hind, 1990; Nelson et al., 2011; Yin et al., 2020). PWID have been disproportionately affected by hepatitis A outbreaks in the United States (Foster et al., 2018) and have an increased risk of severe illness from COVID-19 (Baillargeon et al., 2020). Despite recommendations for hepatitis A and hepatitis B vaccination for PWID and annual recommendations for influenza vaccination, susceptibility to these vaccine-preventable diseases remains unacceptably high (Carey et al., 2005; Figgatt et al., 2020; Frew et al., 2021; Koepke et al., 2019; Lum et al., 2008).

PWID experience barriers to accessing health care in traditional clinical settings. In addition to cost and transportation barriers (Miller-Lloyd et al., 2020), some PWID are reluctant to seek care because of previous negative experiences with health care providers (Allen et al., 2020; Frost et al., 2021; Summers et al., 2018). Lessons learned from hepatitis A outbreaks show that working with trusted communicators and bringing vaccine to locations where people already receive services are key strategies to effective vaccination efforts (Montgomery et al., 2021; Snyder et al., 2019; Wooten, 2019). For these reasons, syringe services programs (SSPs) are ideally situated to offer vaccinations to PWID.

SSPs are programs that provide access to and disposal of sterile syringes and injection equipment in addition to other services to reduce infection, injuries, and overdoses related to using drugs. Comprehensive SSPs are an important strategy for reducing infections related to injection drug use such as HIV and hepatitis C virus (HCV) (Des Jarlais et al., 2020; Thakarar et al., 2020). SSPs can serve as an important source for primary care services for PWID (Burr et al., 2014; Heinzerling et al., 2006) and can play an important role during viral hepatitis outbreaks (Bialek et al., 2005; Stevenson et al., 2001). With the partial removal of a ban on federal funding for SSPs in 2016, the number of SSPs has grown (Bixler et al., 2018; Des Jarlais et al., 2020). However, funding for SSPs can be tenuous (Jones, 2019), and staffing capacity and resources for offering clinical services, such as venipuncture for HCV testing or medications for opioid use disorder, are variable (Behrends et al., 2018). Federal funding can be used to support SSPs but not for the purchase of needles or syringes (Adams, 2020). The capacity for offering vaccinations and the opportunities for scaling up vaccination services in SSPs are not well understood. Our aim was to describe barriers and opportunities for SSPs to offer vaccinations to PWID and to assess the resources needed to overcome those barriers.

During June–August 2021, the Centers for Disease Control and Prevention (CDC) partnered with a national advocacy and capacity building organization to conduct a multistate, cross-sectional survey of SSPs in the United States. An invitation to SSP directors or their designee to participate was disseminated to SSPs through the national organization’s email listservs and CDC’s health department partners. Participants were eligible if they were 18 years of age or older, could read English, and had been working at the SSP for at least 6 months. One response was allowed per SSP. Participants were provided a $40 e-gift card for participation. We used purposive sampling, a nonprobability sampling method, to ensure that at least one SSP was included from all ten Department of Health and Human Services (HHS) regions (Department of Health and Human Services, 2022) by conducting additional outreach efforts to SSPs in HHS regions with low (0–1) responses.

The survey included questions about SSP characteristics, client demographics, existing vaccination resources, resource needs, and staff perspectives on client vaccination barriers (Supplemental File). SSP providers were asked whether they currently offer vaccinations on site. SSPs with on-site vaccinations were asked additional questions about current vaccination practices. SSPs without on-site vaccinations were asked about resources needed to start vaccination services. CDC determined this study to be public health evaluation not requiring institutional review board review. All participants provided written consent.

Descriptive analyses on SSP characteristics, existing vaccination resources, resource needs, and client vaccination barriers were performed for SSPs with and without on-site vaccinations. Median and interquartile range (IQR) were calculated for continuous variables and frequency and percentage for categorical variables. The difference in percentage between SSPs with on-site vaccinations and without was tested with Pearson’s chi-square test, and the difference in median was tested with nonparametric test for location (Wilcoxon two-sample test). All tests were two-sided, and a p-value of ≤ 0.05 was considered statistically significant. Missing responses were excluded from analysis. Statistical analysis was conducted using SAS software version 9.4 (SAS Institute Inc.).

In total, 105 SSPs participated in the survey. Overall, 46 SSPs (43.8%) reported having on-site vaccinations and 59 (56.2%) reported not having on-site vaccinations. Respondents worked at SSPs from 34 states in all 10 HHS regions (region 1, n = 8; region 2, n = 11; region 3, n = 13; region 4, n = 19; region 5, n = 16, region 6, n = 5; region 7, n = 2; region 8, n = 10; region 9, n = 10, region 10, n = 11).

In this descriptive survey of SSPs in the United States, we identified specific barriers and opportunities to increase vaccination services at SSPs. CDC recommends using an integrated approach to offer services to address infectious disease, behavioral, and mental health needs of PWID (Centers for Disease Control and Prevention, 2012). Previous studies have demonstrated that offering vaccinations at SSPs is feasible and acceptable (Altice et al., 2005; Stancliff et al., 2000), including during the COVID-19 pandemic (Heidari et al., 2022). Hepatitis B vaccination programs at SSPs can be cost-saving to health care systems (Hu et al., 2008). Offering integrated clinical services at SSPs allows PWID to access services in a supportive, convenient, and judgement-free environment (Carnes et al., 2021; Frost et al., 2021). In our survey, most SSPs agreed on the need for offering vaccinations to PWID. However, most SSPs that participated in our survey do not currently offer on-site vaccination services. This presents an important opportunity to improve protection against vaccine preventable diseases among PWID if current barriers can be appropriately addressed. SSPs regularly operate with constrained funding, which has been further constrained by COVID-19 (Wenger et al., 2021). Resource needs in our survey included vaccination tracking systems, supplies, vaccines, and storage equipment and were overall greater among SSPs without on-site vaccinations. Resource needs were heterogeneous for SSPs with and without on-site vaccinations, with no consensus on a single most important need. However, SSPs reported a clear consensus on the need for more licensed vaccination staff as the single most important staffing need.

Several SSP characteristics were common among those offering on-site vaccinations. SSPs with on-site vaccinations were more likely to have a fixed site model, to be operated by a health department, and to be in a rural area. In contrast, SSPs without on-site vaccinations had a larger number of client visits and were more likely to offer mobile services or secondary delivery (providing clients with supplies to distribute to their peers) and to be operated by community-based organizations. Offering on-site vaccinations requires a minimum set of infrastructure and personnel, including licensed clinical staff, space for confidential conversations (e.g., exam rooms), and equipment to store vaccines. SSPs with existing infrastructure for clinical services are likely better resourced to offer vaccination services. Peer-delivery models are important for expanding access to sterile injection supplies but face larger challenges in offering vaccination services, which could be addressed by offering vaccination training to peers and providing equipment to maintain and monitor vaccine storage and handling requirements. To expand vaccination services for PWID who access SSPs, future efforts will need to meet the needs of larger SSPs operated by community-based organizations.

The need for more staff who are licensed to administer vaccines was the most consistent staffing need across SSPs with and without on-site vaccinations. The lack of licensed staff poses a critical barrier to expanding vaccination services to PWID in SSPs. During the COVID-19 pandemic and hepatitis A outbreaks, some public health jurisdictions expanded the types of providers who are permitted to administer vaccines (Montgomery et al., 2021; Tewarson et al., 2021). Outside of outbreak settings, expanding the number of personnel who are licensed to administer vaccines, such as community health workers, emergency medical technicians, phlebotomists, and students in health care professions, would improve vaccination access in SSPs. In addition to needing licensed vaccination staff, SSPs without on-site vaccinations had notably higher needs for staff training on preparing and administering vaccines, managing vaccine administration data, and storing and handling vaccines than SSPs with on-site vaccinations. CDC and partners have developed free vaccination training resources that can be used to fill this gap, provided that other barriers (e.g., staffing, funding) can be addressed (Centers for Disease Control and Prevention, 2019; Immunization Action Coalition, 2021). The most common training request for SSPs with on-site vaccinations was for motivational interviewing on how to address client vaccination questions. Requests for other staff training were less common, suggesting that motivational interviewing is missing in some trainings for licensed vaccination staff. Efforts to increase the number of licensed vaccinator staff should be accompanied by adequate training, including how to discuss vaccinations with clients.

Our survey highlights the important role of partnerships with health departments and health systems in offering vaccinations through SSPs. Few SSPs with on-site vaccinations received grants to cover vaccination costs, few were enrolled as 317 adult vaccine providers (the federal funding program to purchase vaccines for underinsured or uninsured adult populations), and few purchased vaccines directly from manufacturers. Health departments were the most common source of vaccines for SSPs with on-site vaccinations. Most SSPs without on-site vaccinations partnered to refer clients to nearby locations for vaccinations, often with health departments and health clinics; however, offering preventive services on-site rather than by referral improves convenience and can improve uptake of vaccine (Campbell et al., 2007; Des Jarlais et al., 2001; Frost et al., 2021; Hood et al., 2020). When staff or other resources are lacking, SSPs should consider bringing outside clinical staff and resources on site through partnerships with health departments and health systems.

SSP staff reported competing priorities as one of the most common client barriers to vaccinations. Offering vaccinations at SSPs will be unsuccessful if there is no client demand for vaccinations. This barrier can be at least partially addressed by simultaneously assessing and meeting individuals’ competing needs. This might require addressing active addiction or offering meals, modest incentives, transportation, or connections to housing and other social services (Allen et al., 2020; Carnes et al., 2021). Empowering SSPs to simultaneously address individuals’ competing needs cannot guarantee vaccination acceptance; however, existing evidence suggests that increases in vaccination acceptance are possible. Several studies, including two randomized controlled trials among PWID, have found that offering monetary incentives resulted in higher hepatitis B vaccination completion than regular outreach (Seal et al., 2003; Stitzer et al., 2010; Topp et al., 2013). Other strategies to maximize the convenience of vaccinations have been shown to improve vaccination rates. These include providing vaccinations on site rather than by referral and, for hepatitis B, offering screening and vaccination simultaneously (Bowman et al., 2014; Campbell et al., 2007; Des Jarlais et al., 2001; Hu et al., 2008). SSPs are established to meet the needs of PWID. To accomplish this, SSPs will need support to provide a comprehensive range of services, outside of vaccination services and supplies alone.

This report is subject to limitations. Accurately estimating the number and characteristics of SSPs operating in the United States is difficult because a comprehensive list of all SSPs in the United States does not exist. We included indirect recruitment channels (e.g., distribution to contacts of contacts) and were unable to determine the number of SSPs contacted or a response proportion. The North America Syringe Exchange Network (NASEN) is trusted in the field, and their network, while optional to join, is seen as the most accurate enumeration of programs. In June 2021, NASEN listed 367 SSPs located in the United States, which gives an estimated 28.6% (105/367) response. Because of nonresponse bias, it is unclear whether SSPs that participated resemble SSPs that did not, which might limit the generalizability of our findings. SSPs with more limited resources and staffing might have been less likely to respond to the survey, which would result in underestimation of resource and staffing needs in our survey responses. SSPs with an interest in vaccinations might have been more likely to participate in the survey, which would overestimate responses to questions about the importance of vaccinations. Demographic data collection is not standardized across SSPs (e.g., transgender status), which could limit data quality. We focused on vaccinations that are offered on site as opposed to through referral off site; however, there remains considerable variability in how and when vaccinations are offered on site that impact vaccination uptake. The survey was conducted during the COVID-19 pandemic after COVID-19 vaccine became available. This might have influenced existing resources, vaccine access, or perceptions of vaccinations. Respondents could have been responding to questions in the context of COVID-19 vaccine rather than vaccines generally. Lastly, client barriers to vaccination were assessed indirectly. Additional work is needed to determine client needs and barriers directly.

This cross-sectional, descriptive survey identified missed opportunities to reduce vaccine-preventable diseases among PWID by offering vaccination services at SSPs. Larger volume SSPs, those operated by community-based organizations, and those located in urban areas, have the greatest potential to benefit from an investment of resources. Critical staffing gaps, particularly for licensed vaccination staff will need to be addressed to expand vaccination services in SSPs. The diverse resource and staffing needs identified in the survey emphasize that solutions to address missed vaccination opportunities in SSPs will require a comprehensive approach. This can be achieved through greater investment of resources in SSPs, by strengthening SSP partnerships with nearby health departments and health systems, and by reexamining the types of providers who are licensed to administer vaccines.