BACKGROUND: People experiencing homelessness (PEH) are underrepresented in public health and clinical research. Study methods that can improve participation by this group are needed. METHODS: In late 2022, the Centers for Disease Control and Prevention conducted an mpox serological survey using venipuncture among PEH in San Francisco, California. Blood collection by a minimally invasive device was offered if venipuncture was not possible or preferred. Participants who had a successful blood draw using the device were asked about device acceptability. RESULTS: Of the 209 successful blood collections, 137 (66%) were among participants who underwent venipuncture and 72 (34%) were among participants who used the device. Use of the device increased overall blood collection participation by 53%. Participants reported high acceptability and preference for the device over venipuncture. CONCLUSIONS: Minimally invasive blood collection devices may increase participation and representation of PEH in serosurveys.

Homelessness increases the risk of acquiring an infectious disease. We conducted a systematic review of the literature to identify quantitative data related to infectious diseases and homelessness. We searched Google Scholar, PubMed, and SCOPUS for quantitative literature published from January 2003 through December 2022 in English from the United States and Canada. We excluded literature on vaccine-preventable diseases and HIV because these diseases were recently reviewed. Of the 250 articles that met inclusion criteria, more than half were on hepatitis C virus or Mycobacterium tuberculosis. Other articles were on COVID-19, respiratory syncytial virus, Staphylococcus aureus, group A Streptococcus, mpox (formerly monkeypox), 5 sexually transmitted infections, and gastrointestinal or vectorborne pathogens. Most studies showed higher prevalence, incidence, or measures of risk for infectious diseases among people experiencing homelessness as compared with people who are housed or the general population. Although having increased published data that quantify the infectious disease risks of homelessness is encouraging, many pathogens that are known to affect people globally who are not housed have not been evaluated in the United States or Canada. Future studies should focus on additional pathogens and factors leading to a disproportionately high incidence and prevalence of infectious diseases among people experiencing homelessness.

Public health problems cannot be addressed without timely and accurate data. However, data that provide insight into populations that may be at disproportionate risk for disease, including people experiencing homelessness, are insufficiently captured. Although the associations between homelessness and disease have been well documented,1-6 data on housing status are not universally or consistently collected in routine public health data.7 Improving collection of data on housing status in public health data collection efforts is necessary to address health disparities among people experiencing homelessness and advance health equity research and practice. | Collecting data related to homelessness and disease is complicated for several reasons, but one of the most salient reasons is that defining homelessness is challenging. Several federal agencies use their own definitions to identify people who might be eligible for assistance programs, creating confusion about which definition should be used for public health purposes. In addition, definitions of homelessness at federal agencies have changed over time, further complicating the collection of homelessness data. The US Department of Housing and Urban Development (HUD) defines homelessness as lacking a fixed, regular, and adequate nighttime residence8; this definition includes both people with a primary nighttime residence of a public or private place not meant for human habitation (eg, cars, parks, public spaces, abandoned buildings) and people residing in temporary shelters (eg, emergency homeless shelter, transitional housing). The US Department of Education (DOE) uses a broader lens, defining homelessness to include school-aged children whose housing situation meets the HUD criteria for homelessness while also including those who share housing with other people by doubling up or couch surfing; those who live in motels, hotels, or trailer parks; and those who are abandoned at hospitals.9

Mpox has affected many communities in the United States (U.S.), including people experiencing homelessness (PEH). Mpox vaccination has been an important tool to disrupt transmission and protect communities at risk of infection. To better understand mpox vaccine knowledge and attitudes, we surveyed 273 PEH and people accessing homeless service sites in San Francisco. Among 64 participants previously offered mpox vaccination, 38 (59 %) had received the vaccine. Among 209 participants not previously offered mpox vaccination, 108 (52 %) reported they would receive the vaccine. Vaccine acceptance was higher among transgender female participants and among male participants who reported male sex partner preference (MSM). Half of participants who declined vaccination identified that perception of personal risk and vaccine education may increase their likelihood of receiving an mpox vaccine. Leveraging trusted information sources to provide risk communication and vaccine education may increase vaccine uptake among PEH.

Monkeypox (mpox) is a disease caused by an Orthopoxvirus. The 2022 multinational outbreak, which began in May 2022, has spread primarily by close skin-to-skin contact, including through sexual contact. Persons experiencing homelessness have been disproportionately affected by severe mpox (1). However, mpox prevalence and transmission pathways among persons experiencing homelessness are not known, and persons experiencing homelessness have not been specifically recommended to receive mpox vaccine during the 2022 outbreak (2,3). During October 25-November 3, 2022, a CDC field team conducted an orthopoxvirus seroprevalence survey among persons accessing homeless services or staying in encampments, shelters, or permanent supportive housing in San Francisco, California that had noted at least one case of mpox or served populations at risk. During field team visits to 16 unique sites, 209 participants completed a 15-minute survey and provided a blood specimen. Among 80 participants aged <50 years who did not report smallpox or mpox vaccination or previous mpox infection, two (2.5%) had detectable antiorthopoxvirus immunoglobulin (Ig) G antibody. Among 73 participants who did not report mpox vaccination or previous mpox infection and who were tested for IgM, one (1.4%) had detectable antiorthopoxvirus IgM. Together, these results suggest that three possible undetected mpox infections occurred among a sample of persons experiencing homelessness, highlighting the need to ensure that community outreach and prevention interventions, such as vaccination, are accessible to this population.