Abstract
Objectives:
Mobile medical units (MMUs) provide health care services in the community to reach populations with geographic, financial, and other barriers to care. The US Department of Veterans Affairs (VA) Homeless Patient Aligned Care Team (HPACT) program deployed MMUs to 25 sites in fiscal year 2024 to increase access for veterans experiencing homelessness. We examined early implementation of MMUs in HPACT sites by describing implementation and operational issues, services provided, and characteristics of veterans who used MMUs.
Methods:
To examine the implementation of MMUs on veterans experiencing homelessness, we conducted a mixed-methods study using an online survey and health care administrative data. Measures included MMU implementation time, staffing type, services, safety measures, maintenance costs, and characteristics of veterans using and not using MMUs. We examined differences between veterans who used MMUs and those who did not.
Results:
Seventeen of 25 sites responded to the survey; MMU implementation occurred during a mean of 147 hours in 5 months. Most sites (15 of 17) visited housing sites and homeless shelters in community- and VA-supported programs to provide health screenings, education, and medication administration and prescribing. Operating costs varied widely for vehicle maintenance and gas and medical and telehealth equipment. Veterans who used MMUs (vs did not use MMUs) had more medical comorbidities (Elixhauser score of 3.4 vs 2.8), were more likely to have substance use disorder (49.9% vs 39.1%), and had higher baseline levels of health care use, especially emergency department visits (0.4 vs 0.3 visits per quarter).
Conclusions:
Evidence on the effects of MMUs on patient engagement with primary and mental health care and acute care use is needed to inform decisions to implement MMUs.
Keywords: homeless, veterans, mobile medical units, implementation
Some people in the United States experience geographic, social, or structural barriers to accessing health care.1-3 Mobile medical units (MMUs), also called mobile health clinics, are vehicles converted into spaces for providing medical treatment to people with barriers to accessing care in traditional settings. MMUs have increasingly been implemented by hospitals and nonprofit organizations during the past 2 decades.4 -6
Past evaluations of MMU programs have mainly focused on describing patient populations and the types of services provided. MMUs frequently provide primary care, urgent care, and preventive health services.4 -9 Patients obtaining MMU care often include those with substance use disorders or mental health issues and those living in low-income areas. MMUs have been used to provide both population-based public health screening10,11 and outreach for specific diseases, such as kidney disease,5,8 HIV, 12 stroke, 13 and substance use and psychiatric disorders.14 -16 Few studies have examined the implementation of MMU programs, including resources spent on planning and developing programs, resources required to operate MMUs, locations visited, and health care providers’ perceived benefits and challenges of MMUs.
The proliferation of MMUs has opened up a new specialty of street medicine, providing care to people experiencing homelessness. A systematic review of MMUs for people experiencing homelessness found that various types of MMUs provided primary care, substance abuse treatment, and other health care and social services. 17 The review concluded that further research is needed to determine the effectiveness of MMUs and to understand what differentiates people experiencing homelessness who do and do not use MMUs.
The US Department of Veterans Affairs (VA) health care system provides health care to eligible veterans and provides various supports to overcome barriers to care, including MMUs, to reach veterans in primarily rural areas. In the VA system, more than 60 VA medical centers provide more tailored care than general primary care to veterans experiencing homelessness through a patient-centered medical home model called Homeless Patient Aligned Care Teams (HPACT).18,19 HPACT consists of specialized medical care teams that are often embedded with other programs (eg, housing programs) to serve veterans experiencing homelessness. HPACT teams maintain small panels, provide interdisciplinary care, offer flexible scheduling, conduct community outreach, and provide services such as food assistance and transportation to improve access to and use of VA primary care for veterans experiencing homelessness. 20
To provide more accessible care to veterans experiencing homelessness outside of VA clinics and hospitals and enable more extensive outreach in the community, the national HPACT program began a new MMU program in October 2023 to provide services to veterans experiencing homelessness in outfitted vans and other large vehicles in community settings. MMU vehicles were rolled out to sites on a staggered basis through 2024 and planned for a total of 25 sites. The MMUs were intended to serve as an adjunct, not a substitute, to traditional clinic-based care.
In this study, we examined the early implementation of MMUs for veterans experiencing homelessness by using a mixed-methods design based on a survey of MMUs and patient-level administrative data at HPACT sites that implemented the new MMU program. We described the types of services provided by MMUs and identified key implementation issues. We also compared the characteristics of veterans experiencing homelessness treated in MMUs versus other veterans experiencing homelessness in the same VA medical centers. The results may inform continued implementation of VA MMU programs at other HPACT sites and may provide a roadmap for MMU programs outside the VA system to understand the resources needed for planning and development, staffing, operations, services provided, and the characteristics of patients served.
Methods
Study Cohort and Data Sources
Twenty-five VA medical centers agreed to participate in the MMU program and either provided MMU services or planned MMU services in the first year of the program. With support from the VA Homeless Programs, the MMU program launched nationally in fiscal year 2024, 21 although the timing in which VA medical centers received MMUs on site varied widely. Each VA medical center implemented its MMU following on-site vehicle delivery and deployed it for use according to local needs and arrangements. All MMU vehicles were equipped with basic medical equipment, and VA medical centers could supply and pay for any additional equipment they wanted. The VA Homeless Programs Office determined that this project was a quality improvement project that did not require institutional review board assessment. As a quality improvement, nonresearch activity, this project did not require ethics approval.
For the purposes of evaluating the MMU program, all 25 sites were asked to respond to a survey to share their experience in implementing and providing MMU services; however, 5 sites had not received their MMU or provided any services through their MMU at the time of the survey. The patients in this analysis included all patients identified as experiencing homelessness through the VA Homeless Registry in MMU sites that provided MMU care in fiscal year 2024 (N = 20).
Data sources included the MMU survey and VA administrative data on patient demographic characteristics from the VA Observational Medical Outcomes Partnership files. 22 We obtained data on VA health care use from the VA Corporate Data Warehouse Inpatient and Outpatient files (unpublished) from the baseline year prior to MMU implementation in fiscal year 2023.
Survey Methods
We fielded a voluntary online survey via REDCap to all 25 sites that agreed to participate in the MMU program during July–September 2024 and requested only 1 response per site. The survey was distributed through an email listserv to all sites, and respondents in any role could respond. We conducted follow-up 3 times on the listserv for several weeks to increase the response rate. While respondents remained anonymous, the survey asked participants to identify their role in MMU operations and their VA facility. The survey included open- and closed-ended questions on time spent planning and developing their programs, staffing MMUs, disseminating services, conducting safety measures (5-point Likert-type scale ranging from very unsafe to very safe), and tracking vehicle maintenance costs. The survey also included an open-ended question on other implementation issues encountered. We summarized quantifiable survey responses (eg, number of hours and days, number of full-time–equivalent employees, costs) with the mean and SD of all nonmissing responses, and we summarized categorical responses as frequencies. We summarized open-ended responses based on major themes.
Administrative Data Methods
We identified MMU encounters and patients who used MMUs by the designated MMU program code in VA outpatient records in fiscal year 2024 (October 1, 2023–September 30, 2024). In 20 sites that provided MMU services in fiscal year 2024, we identified all patients experiencing homelessness as those with a prior diagnosis of homelessness in VA use records or use of homeless program services in fiscal year 2023. 22 We collected data on the following baseline demographic characteristics of patients: age, sex, race and ethnicity, marital status, VA enrollment priority group (based on service-connected disability rating and VA means test), and rurality. We also collected data on chronic medical and mental health conditions and substance use disorders. We calculated an Elixhauser comorbidity score based on all diagnosis codes from VA inpatient and outpatient encounter records from the baseline year (fiscal year 2023). 23 Finally, we examined patients’ VA inpatient and outpatient care categorized by type of care and total VA costs of care in the baseline year.
We summarized the mean value or percentage of patients with a given characteristic for patients with any MMU care or without any MMU care and conducted the Pearson χ2 test for categorical variables and analysis of variance test for continuous variables to determine differences between groups and significance at the P < .05 level.
Results
MMU Implementation and Operations
The overall MMU survey response rate was 68% (17 of 25 sites), although several respondents did not respond to every question. The 16 respondents who answered the question on their role at the MMU indicated such roles as primary care provider, social worker, nurse manager, mental health specialty programs director, homeless primary care program coordinator, and physician. MMU sites reported a mean time spent planning and developing their MMU launch of 147 total hours, or a mean (SD) of 7 (6) hours per week during a 21 (16)-week period. MMUs operated a mean (SD) of 1.2 (0.8) days per week and 4.1 (2.5) hours per operating day. The most common MMU locations were VA-funded Grant and Per Diem sites (community housing sites for veterans experiencing homelessness; n = 11), homeless shelters (n = 11), and US Department of Housing and Urban Development–VA Supportive Housing program sites (n = 10) (Figure 1). MMUs were mostly staffed by primary care providers, social workers, and registered nurses; multiple provider types delivered MMU care together (Table 1). Few peer support specialists, licensed practical nurses/licensed vocational nurses, pharmacists, medical support assistants, and psychiatrists staffed MMUs.
Figure 1.
Locations visited by VA mobile medical units (MMUs) (n = 17 sites) for veterans experiencing homelessness, fiscal year 2024. Other includes community engagement events, American Legion posts, Stand Down events, and transportation centers. Abbreviations: HUD-VASH, US Department of Housing and Urban Development–VA Supportive Housing; VA, US Department of Veterans Affairs.
Table 1.
Type of health care providers and staff at VA mobile medical units (MMUs) for veterans experiencing homelessness, fiscal year 2024 (n = 16 sites) a
| Provider/staff position | No. (%) of MMUs with provider/staff position | Mean no. (SD) [range] of full-time equivalents |
|---|---|---|
| Primary care provider | 13 (81) | 0.1 (1.0) [0.4-0.7] |
| Social worker | 11 (69) | 0.1 (1.0) [0.5-0.9] |
| Registered nurse | 10 (63) | 0.5 (1.0) [0.2-0.9] |
| Licensed practical/vocational nurse | 4 (25) | 0.1 (1.0) [0.4-0.8] |
| Peer support specialist | 4 (25) | 0.1 (1.0) [0.3-0.5] |
| Pharmacist | 3 (19) | 0.1 (1.0) [0.4-0.4] |
| Medical support assistant | 3 (19) | 0.5 (1.0) [0.2-0.8] |
| Psychiatrist | 1 (6) | 0.1 (0.0) [0.0-0.1] |
Abbreviation: VA, US Department of Veterans Affairs.
One site did not respond to this question.
MMU sites used various methods to notify veterans of MMU services and schedules, relying primarily on homeless program referrals (n = 13), HPACT teams (n = 12), community partners (n = 10), and word of mouth (n = 9). Among MMU services provided, the most common were health screenings (n = 14), health education (n = 14), medication administration and prescribing (n = 12), and vaccinations (n = 9) (Figure 2). Few MMUs provided housing services (n = 5) or care for mental health/substance use disorders (n = 6).
Figure 2.
Services provided by VA mobile medical units (MMUs) (n = 17 sites), fiscal year 2024. Abbreviation: VA, US Department of Veterans Affairs.
Site Safety and Operating Costs of MMUs
Most MMUs had safety measures in place to protect staff. Common safety measures included safety training; requiring staff to work in pairs, use personal digital safety protection devices (eg, SoloProtect), and have cell phones; and using secure boxes for controlled substances and supplies. Less common safety measures included participation in the VA Emergency Alerting and Accountability System, driver/roadside emergency training, vehicle tracking, protocols for aggressive patients, and working with a suicide prevention coordinator in the event of suicidal patients. With these safeguards in place, 6 survey respondents indicated they felt very safe, 7 felt moderately safe, 3 were neutral, and 1 felt moderately unsafe.
Seven sites did not report costs of MMU operations and equipment during the past 6 months, and the 10 sites that did report costs varied widely in costs. Sites reported a mean (SD) [range] of costs for the following: vehicle maintenance was $3360 ($8183) [$200-$25 000], gas was $724 ($1435) [$70-$5000] per month, medical equipment was $16 206 ($42 021) [$0-$127 374], and telehealth equipment was $173 ($349) [$0-$1057]. Other operating costs reported by sites included costs for dedicated medical supplies, trash cans, towing for repairs, tables, recreational vehicle hosing, septic tank management, and WiFi routers; these costs were a mean (SD) [range] of $1084 ($771) [$60-$2000]. Because MMU vehicles were already equipped with basic medical equipment, only a few sites paid for additional equipment and tracked these costs.
Site Benefits and Challenges of MMUs
Overall, survey respondents expressed positive experiences with the MMU program, specifically its effect on expanding outreach, improving collaboration, building relationships, and receiving interest from veterans not otherwise engaged with the VA. One medical director commented that MMUs are “absolutely needed to fully support the outreach arm of HPACT,” and a social work supervisor observed that the MMU program “has generated broad interest and attention to the great work [they] already do in the homeless program and are in the process of developing.”
However, sites noted operational difficulties related to running and maintaining MMUs. Several sites mentioned that the process of launching their MMU was slower and more extensive than anticipated, with some vehicles immediately needing maintenance that prevented them from deploying right away. One site called the MMU rollout a “bit of a disaster” because of ongoing mechanical issues, and another site remarked that their MMU was in the shop more often than on the road.
Staffing was a frequent concern, namely, the need for dedicated staff and administrative or facilities operations support to relieve clinicians from the logistics of maintaining MMU vehicles. One respondent commented that “it should not be underestimated how much time it takes our HPACT [registered nurse] to ensure the MMU remains operational, which takes away time to manage our panel.” Several sites shared that they were in the process of developing standard operating procedures so that MMU providers and staff and program partners were formally informed and aware of their responsibilities toward the MMU. Another site mentioned having to “get creative on how to provide services with the staff [they] have, especially now with all the budgetary concerns and no new positions being approved.”
Sites also commented on the lack of transparency concerning vehicle maintenance and operational costs. Many sites wanted to better understand how equipment needs for the MMUs are funded. One site mentioned that the vehicle’s air conditioner was loud and made it difficult to hear patients and that they were still waiting for an automated external defibrillator and keychain horns for staff safety. A few sites mentioned unstable WiFi connectivity and that equipment provided on MMUs was sometimes inadequate.
Despite these reported issues, respondents were overall enthusiastic and said that the MMU initiative was a welcome addition to the VA’s homeless program. As an HPACT coordinator commented, the MMU is “just starting to scratch the surface of what [they] can do,” and many sites expressed optimism for the initiative as it matures.
Characteristics of MMU Patients at MMU Sites
A total of 414 veterans experiencing homelessness visited an MMU in the first year of implementation. They had a mean (SD) of 1.5 (1.2) MMU visits at 20 sites that provided MMU services. Veterans experiencing homelessness who used any MMU services had a mean (SD) age of 61.3 (12.6) years; veterans experiencing homelessness who did not use any MMU services had a mean (SD) age of 54.6 (15.5) years (Table 2). One-fifth (20.6%) of MMU patients were assigned to HPACT primary care, slightly more than half of MMU patients (55.0%) were assigned to a general PACT, and nearly three-quarters (73.6%) of non-MMU patients were assigned to a general PACT. Almost one-quarter (24.4%) of MMU patients, compared with one-fifth (19.7%) of non-MMU patients, were not assigned to any primary care team. A significantly larger proportion of MMU patients than non-MMU patients were male, Black, not currently married, eligible for VA care through the means test or Medicaid eligibility, and living in urban areas (P < .001). Compared with non-MMU patients, MMU patients had significantly higher overall comorbidity and higher rates of most substance use disorder conditions, arthritis, chronic obstructive pulmonary disease, diabetes, headache, hepatitis C, hypertension, ischemic heart disease, prostatic hyperplasia, pneumonia, and renal failure (P < .001) (Table 2).
Table 2.
Characteristics of veterans experiencing homelessness in mobile medical unit (MMU) sites (N = 20), fiscal year 2023 a
| Characteristic | Non-MMU patients b (n = 137 860) | MMU patients c (n = 1414) | P value d |
|---|---|---|---|
| Age, mean (SD), y | 54.6 (15.5) | 61.3 (12.6) | <.001 |
| Patient Aligned Care Teams assignment, % | <.001 | ||
| Homeless Patient Aligned Care Teams (HPACT) | 6.7 | 20.6 | |
| Patient Aligned Care Teams (PACT) | 73.6 | 55.0 | |
| No PACT/HPACT | 19.7 | 24.4 | |
| Sex, % | <.001 | ||
| Female | 13.3 | 5.9 | |
| Male | 86.2 | 93.9 | |
| Race and ethnicity, % | <.001 | ||
| Black | 38.6 | 43.3 | |
| Hispanic | 7.6 | 5.5 | |
| White | 43.6 | 40.3 | |
| Other race | 3.0 | 3.6 | |
| Unknown or missing | 7.6 | 8.0 | |
| Marital status, % | <.001 | ||
| Divorced/separated/widowed | 44.7 | 49.4 | |
| Married | 22.0 | 15.1 | |
| Single | 31.7 | 34.1 | |
| Priority group, % | <.001 | ||
| 1: 50% to 100% service connected | 37.4 | 19.4 | |
| 2: 30% to 40% service connected | 5.9 | 3.5 | |
| 3: 10% to 20% service connected | 11.1 | 10.9 | |
| 4: Aid and attendance/catastrophic disease | 3.6 | 5.0 | |
| 5: Means test/Medicaid eligible | 26.8 | 34.1 | |
| 6: World War I/Mexican Border/Gulf War veteran, 0% service connected | 0.9 | 0.9 | |
| 7-8: Not service connected, above means test | 8.3 | 7.6 | |
| Missing | 5.9 | 18.6 | |
| Rurality, % | <.001 | ||
| Urban | 86.0 | 89.9 | |
| Rural/highly rural | 14.0 | 10.1 | |
| Elixhauser comorbidity score, mean (SD) e | 2.8 (2.6) | 3.4 (2.8) | <.001 |
| Any substance use disorder condition, % | 39.1 | 49.9 | <.001 |
| Any mental health condition, % | 56.7 | 48.5 | <.001 |
| Dual substance use disorder/mental health, % | 29.5 | 32.9 | .01 |
| Substance use disorder conditions, % | |||
| Alcohol | 24.6 | 31.5 | <.001 |
| Opioid | 5.8 | 7.9 | .002 |
| Cannabis | 13.0 | 15.1 | .03 |
| Cocaine | 9.2 | 18.4 | <.001 |
| Sedative/hypnotic | 1.0 | 0.8 | .57 |
| Stimulant | 7.5 | 12.4 | <.001 |
| Nicotine | 17.2 | 26.1 | <.001 |
| Other psychoactive | 6.4 | 9.2 | <.001 |
| Mental health conditions, % | |||
| Serious mental illness | 14.8 | 15.9 | .28 |
| Dementia | 1.5 | 1.4 | .76 |
| Anxiety | 27.6 | 21.9 | <.001 |
| Bipolar/manic | 8.3 | 6.8 | .07 |
| Major depression | 15.1 | 15.9 | .43 |
| Other mood disorder | 7.0 | 7.7 | .36 |
| Attention deficit hyperactivity disorder | 3.5 | 1.6 | <.001 |
| Posttraumatic stress disorder | 32.9 | 24.1 | <.001 |
| Schizophrenia/related | 8.1 | 10.3 | .01 |
| Medical conditions, % | |||
| Acid-related diseases | 16.0 | 16.5 | .62 |
| All cancers | 7.1 | 7.8 | .34 |
| Arthritis | 12.1 | 16.3 | <.001 |
| Asthma | 4.4 | 4.5 | .93 |
| Chronic obstructive pulmonary disease | 10.0 | 16.5 | <.001 |
| Congestive heart failure | 6.0 | 6.1 | .86 |
| Diabetes | 19.0 | 24.2 | <.001 |
| Headache | 11.3 | 8.8 | .01 |
| Hepatitis C | 3.4 | 6.7 | <.001 |
| Hypertension | 38.4 | 51.0 | <.001 |
| Ischemic heart disease | 8.3 | 10.5 | .01 |
| Lower back pain | 28.7 | 27.7 | .45 |
| Peripheral vascular disease | 4.5 | 5.8 | .04 |
| Pneumonia | 2.1 | 3.5 | .001 |
| Prostatic hyperplasia | 9.0 | 13.9 | <.001 |
| Renal failure | 6.6 | 8.9 | .00 |
| Stroke | 5.0 | 6.2 | .08 |
| No. of VA inpatient stays per quarter, mean (SD) | |||
| Medical/surgical | 0.05 (0.3) | 0.08 (0.4) | <.001 |
| Psychiatric | 0.03 (0.2) | 0.04 (0.2) | .001 |
| Observation | 0.02 (0.2) | 0.04 (0.3) | <.001 |
| No. of VA outpatient visits per quarter, mean (SD) | |||
| Primary care | 0.9 (1.5) | 1.0 (1.6) | .03 |
| Mental health | 3.6 (7.5)) | 4.6 (8.4) | <.001 |
| Homeless | 1.2 (3.0) | 2.3 (4.3) | <.001 |
| Mental health intensive case management | 0.1 (1.0) | 0.1 (1.5) | .07 |
| Justice programs | 0.1 (0.7) | 0.1 (0.6) | .05 |
| Specialty care | 0.7 (2.0) | 0.8 (2.5) | .004 |
| Emergency department | 0.3 (0.8) | 0.4 (1.3) | <.001 |
| VA health care costs per quarter, mean (SD), $ | 8539 (29 414) | 12 285 (28 817) | <.001 |
| No prior VA care, % | 12.3 | 2.6 | <.001 |
Abbreviation: VA, US Department of Veterans Affairs.
Data source: VA Corporate Data Warehouse (unpublished data).
Patients in the VA Homeless Registry who did not have any MMU encounters.
Patients had at least 1 MMU encounter; some patients with MMU encounters were not in the VA Homeless Registry.
Using the Pearson χ2 test for categorical variables and analysis of variance for continuous variables, with P < .05 considered significant.
The Elixhauser comorbidity index ranged from 0 to 22. 23
Before implementation of MMUs, MMU patients had higher mean numbers of visits and inpatient stays per quarter of all types of inpatient care, mental health care, specialty care, and emergency department care than non-MMU patients (all P < .01). The proportion of MMU patients who did not have any prior VA use was higher than among non-MMU patients. The mean (SD) costs per quarter prior to MMU implementation were $12 285 ($28 817) for MMU patients and $8539 ($29 414) for non-MMU patients.
Discussion
To our knowledge, this study is the first to examine the implementation of a national MMU program in the VA focused on veterans experiencing homelessness across 20 diverse sites. Sites reported needing an average of 5 months to develop their MMU programs before launching services. Sites also reported high operating costs for vehicle maintenance and gas as well as medical and telehealth equipment, although costs varied widely among sites. Most MMUs visited housing sites for veterans experiencing homelessness in community- and VA-supported programs and homeless shelters. Most MMUs provided health screenings, health education, and medication administration and prescribing, and few MMUs provided specialized care for mental health and substance use disorders or housing services. Many HPACT teams do not include psychiatrists or psychologists or have limited full-time–equivalent employees, so there may be challenges with staffing MMUs with specialty mental health providers. However, MMUs may facilitate referrals to specialty mental health care provided in clinics or through telehealth for patients with unmet needs.
Several MMU providers and staff expressed the benefits of reaching patients experiencing homelessness in the community through MMUs, consistent with the reported experiences of MMU programs outside the VA. 17 However, the long-term sustainability of MMUs at some sites is unclear because several respondents cited issues with MMU staffing, limited services provided by MMUs, and mechanical problems with MMU operation. Thus, some sites may need additional support, and ongoing information sharing of best practices among sites may be useful.
This study is also the first, to our knowledge, to compare a general population of veterans experiencing homelessness and their demographic characteristics and health care use with that of veterans experiencing homelessness who used MMU services. We found evidence that MMUs reached veterans at a higher risk of experiencing homelessness with higher comorbidity, higher rates of substance use disorder and certain medical conditions, and higher baseline use of health care when compared with other veterans experiencing homelessness who did not use MMUs. The reasons why some veterans experiencing homelessness obtained MMU care rather than traditional clinic-based care are unknown. Future work is needed to examine whether veterans experiencing homelessness with less established health care provider relationships were more likely to use MMUs than those with established health care provider relationships. In addition, in comparison with veterans experiencing homelessness who did not use MMUs, those who used MMUs were more likely to have no prior use of VA services; as such, it appears that MMUs were successful at reaching new veterans experiencing homelessness. It is unknown whether MMUs will be effective at providing more timely ambulatory care and referrals to other VA services than traditional clinic-based care. Many MMU patients had high baseline levels of emergency department and inpatient care, so opportunities may exist for MMUs to address time-sensitive health issues before patients seek costly emergency or acute care.
MMUs have the potential to reach patients who have barriers to accessing clinic-based care, especially those not assigned to a VA primary care team in HPACT or regular PACT. Prior MMU programs cited building trust in health care providers as a potential benefit of MMUs. 24 Therefore, the potential of MMUs to care for veterans experiencing homelessness remains to be seen in the continuity of veterans’ care and referral of veterans to appropriate care outside of MMUs.
Based on our findings and the fact that only 20 of 55 HPACT sites implemented an MMU program in the first year, we speculate that some sites were hesitant to use MMUs because of unknown costs of maintenance and operations, concerns about support staff availability, and the logistics of deploying and using MMUs. However, with more information available from this study and as the sites gain more experience with MMUs, other sites may be more willing to participate.
Limitations
This study had several limitations. First, it relied on a self-report survey of designated staff at participating MMU sites, and we could not independently verify the accuracy of responses. Second, we did not measure MMU care for sites that had not yet adopted the designated program code. As such, we may have undercounted patients who used MMUs. Third, operating costs were reported by sites, so we could not verify the completeness of costs reported.
Conclusion
MMUs represent an important way to reach patients with barriers to accessing clinic-based care. More evidence on the effects of MMUs on patients’ engagement with primary care and mental health care and use of acute care is needed for health systems such as the VA to decide to implement MMUs. Veterans are disproportionately represented among people experiencing homelessness, so MMUs may be a vital tool to help end homelessness among veterans.
Footnotes
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Funding for this work was provided by the US Department of Veterans Affairs (VA) National Center on Homelessness Among Veterans and the VA Office of Mental Health and Suicide Prevention. The funding organizations had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication.
Disclaimer: The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of the VA, the US government, or any universities.
ORCID iD: Jean Yoon, PhD, MHS 
https://orcid.org/0000-0001-8565-2881
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