Table 3A.

Intervention outcomes: Randomised controlled trials.

Reference	Outcome(s)	Determinants of Uptake	Enablers and/or Barriers
[34]	There was a decrease in vaccination rate at the clinic site (24.8% in 2017–18 vs. 23.9% in 2018–19). There was a 115% increase in vaccination rate at the shelter/meal sites (N = 13 in 2017–18 vs. N = 28 in 2018–19). Vaccination refusal rate for people included in the intervention was 39.5%, and for people not included in the intervention was 51.9%.	Vaccine acceptance not correlated with gender, age, participation in the intervention, or positive history of vaccination.	Enablers: Multiple vaccination sites; provider collaboration Barriers: Delay in receipt of influenza vaccine from supplier, until after the start of the influenza seasonLack of regular feedback about vaccination rates to staff (slowing impetus to promote vaccination) Medical/social acuity levels of participants may have prevented nurses focusing on preventive care People who are homeless interact with healthcare providers on an irregular/limited basis; mistrust high Lack of confidence in vaccine; lack of consistent emphasis about importance of vaccination; lack of up-to-date information about vaccination Misinformation about vaccination/influenza is prevalent Single nurse unable to see all eligible patients
Brouqui et al., 2010	46.9% (N = 117/249) people received a pandemic flu vaccination, N = 26 received seasonal + pandemic flu vaccination.	Not reported.	Enablers: Participants had good knowledge about benefits of influenza vaccination; participants were “more afraid [of] the disease than … possible vaccine side effect[s]” Barriers: Nil reported
[54]	Patients experiencing homelessness or living in temporary accommodation were administered 120 vaccines in 2015–16, 55 vaccines in 2016–17, 78 vaccines in 2017–18, and 228 vaccines in 2018–19.	Not reported	Enablers: Use of student volunteersDelivered vaccinations at convenient locations (e.g. beneath a well-trafficked city bridge) Barriers:Need to cold-chain the vaccine (2 °C-8 °C)Need to use personal protective equipment (PPE) and screen patients for COVID-19 symptoms prior to entry
[35]	0 vaccinations in historical period, 23 vaccinations in pre-intervention period (vaccination program but no alert), 465 in intervention period (vaccination program and alert). This is equivalent to 0, 9, 184 vaccinations per 1,000 visits by homeless persons. During intervention period, 77.5% of visits where patient received the vaccine, had already received it or it was not indicated; 22.5% of visits where alert was activated but patient did not receive vaccine (e.g. because the vaccine was refused (40.8%) or no reason given). Vaccination rates declined over time, likely due to other vaccination programs operating in the region.	Not reported.	Enablers: Coincided with mass Hepatitis A/vaccination education campaign operated by local public health agency Barriers:Potential impacts on staff work load (e.g. alert fatigue) May have disrupted patient flow/length of stay Delays with pharmacist needing to review vaccine orders
[36]	681 participants received 1/3 doses, 79.1% received 2/3 doses, 50.4% received 3/3 doses.	2 doses: more likely to be female, more likely to be involved in prostitution; 3 doses: more likely to be involved in prostitution. Completion not associated with men who have sex with men, intravenous drug use.	Enablers: Clinics scheduled for the late afternoon/evening to match the times most participants tended to present to sites Clinic times were arranged around the other activities taking place at each site, to avoid disruption Strong links with community workers with access to various hard-to-reach groups of homeless youth Barriers: Participants used clinic/outreach worker to seek assistance outside program scope (e.g. referrals, shelter, etc.) Reaching all eligible participants may take several years
[37]	122 patients, 74% of whom were homeless (N = 90), received a vaccine.	Not reported for people who are homeless.	Enablers: Stored vaccines in refrigerator in emergency department, allowing staff to dispense independent of pharmacy Actively involved all key stakeholders in emergency dept Paper supplies relevant to program in all triage rooms Emergency departments = accessible to patients Barriers: Involved an additional 5–10 min of time per patient
[38]	10,324 vaccines were administered, of which 1385 (13%) were administered to homeless people.	Not reported.	Enablers: Other than the emergency department where vaccines were delivered, patients had limited access to routine care Close coordination between public heath, health, and community agencies to enable outbreak management Barriers: Not reported
[39]	Vaccine accepted by 37/93 = 39.8% of eligible patients.	No differences in ethnicity/other demographic characteristics; patients with 3 + comorbidities more likely to accept; women and those who had previously declined other vaccines less-likely to accept. Primary reasons for declining were lack of insurance, or refusal of all vaccines.	Enablers: Partnering with a local pharmacy Barriers: Participants’ lack of insurance coverage Patient-held beliefs about vaccine necessity/risks Lack of on-site medical freezer Lack of an efficient way to determine vaccine costs and participant insurance coverage First vaccine given at second appointment: there was a need to wait for 5 + doses, or pay $20 shipping fee
[5]	N = 295 people received a vaccine at the crisis centres.	Not reported.	Enablers: 52% were worried about getting influenza 13% considered getting the vaccine convenient 9% had the vaccine recommended by their doctor Barriers: Not specified
[40]	N = 60 (100%) homeless individuals at the shelter received vaccination; this was an increase from 28 vaccinations the previous year. An additional 26 people filled vouchers for vaccination at a local health department.	Not specified.	Enablers: Not specified Barriers: People reported fears and misperceptions of vaccines 32.0% said they did not feel they needed a vaccine 34.0% said they do not like to receive shots 23.0% said they believed the flu vaccine is unsafe 21.0% said they had a previous bad experience with vaccines 38.0% said they were concerned about side-effects 47.0% said they identified ‘other’ barriers to vaccination (e.g. concerns the government was ‘tracking them’) 59.0% said they did not have the money for a vaccine 53.0% said they did not have relevant health insurance 53.0% said they did not have transportation 24.0% said they had problems with mobility 40.0% said they did not know where to get a vaccine
[41]	Of the 533 participants, 528 (98%) received 1x dose of vaccine. After serology, 471 people required vaccination. Of these, 361 (77%) returned for a second dose, and 293 (63%) returned for a third dose.	People who completed three doses more likely to be > 25 years of age, to engage in unprotected anal sex, and to use solvents.	Enablers: Not reported Barriers: Not reported
[47]	Approximately 49% of eligible clients enrolled in the program. Hepatitis A: 108 people commenced the vaccination schedule; 73% (N = 73/100) of people eligible after serology completed the schedule. Hepatitis B: 102 people commenced the vaccination schedule; 75% (N = 69/92) of people eligible after serology completed the schedule.	Not reported.	Enablers: Vaccination was incorporated into routine care The clinic site was considered ‘convenient’ The clinic was already accepted and used by target group Clinic staff/participants were well-known to each otherCounselling (part of pre- and post-serological testing) Barriers: Not reported
[49]	Tetanus, diphtheria: offered to all participants not up-to-date; 93% accepted the vaccination. Hepatitis B: of those eligible for vaccination, 9% had coverage on admission, 63% had coverage on follow-up or completion.	Not reported.	Enablers: Not reported Barriers: Completing the full series of hepatitis B vaccination was difficult because of the 6-month time period required; 13% refused because it required multiple visits Almost all who initially consented received 2 doses of hepatitis B vaccine, but 41% had left the facility before reaching the 6 months required for the 3rd dose; accelerated schedules are ‘highly desirable’ One quarter of people lacked documentation about previous vaccination outside of the clinic site 1.3% of participants had ‘emotional instability’ and could not be effectively counselled about vaccination People often only seek healthcare in ‘emergencies’; routine healthcare may not be a priority Very few participants qualified for financial assistance
[50]	1515 homeless people were vaccinated actively; 41.0% (N = 627) were vaccinated actively and passively. Vaccination coverage was approximately 83.0% (N = 1515/1800) of homeless population. 1,197 social workers and volunteers who work with the homeless were also vaccinated. The Hepatitis A outbreak in Rotterdam was “terminated”.	Not reported.	Enablers: Not reported Barriers: Not reported
[51]	209 people received a vaccination.	Not reported.	Enablers: Not reported Barriers: Female participants were reluctant to receive clinic services beyond mandatory intake physical and screening
[53]	Standard course: 54 patients received a first dose (of those, 52 were eligible for further doses), 23 received a second dose, and 3 received a third dose. Accelerated course: 90 patients received a first dose (of those, 86 were eligible for further doses) , 64 received a second dose, and 35 received a third dose. People receiving the accelerated course were significantly more likely to complete the course (P < 0.0001).	Vaccine acceptance not correlated with age or gender.	Enablers: Accelerated dose requires no change to clinical practice, other than the timing of administration No need for costly postal/telephone reminders Barriers: Not reported