Vaccine acceptance, determinants, and attitudes toward vaccine among people experiencing homelessness: a systematic review and meta-analysis

BACKGROUND

COVID-19 has caused millions of deaths globally, with vulnerable populations such as people experiencing homelessness (PEH) at higher risk. This systematic review and meta-analysis aims to identify the prevalence and key factors contributing to vaccine acceptance experienced by PEH.

METHODS

The protocol of this study was registered in PROSPERO (CRD42023391659). We included studies that reported relevant information about vaccine acceptance or vaccine hesitant/refusal among PEH. Eight databases were systematically searched in January 2023. Meta-analysis was conducted for the prevalence of vaccine acceptance, vaccine uptake, and factors associated with vaccine acceptance. Attitudes toward vaccines were combined into bar charts.

RESULT

A total of 29 papers were included in this systematic review and 19 papers were included for meta-analysis. The pooled prevalence of COVID-19 vaccine acceptance among PEH was 66% (95%CI: 58%-73%). Our meta-regression showed vaccine acceptance was significantly increased over time. Moreover, subgroup meta-analysis showed that PEH were more likely to accept the COVID-19 vaccine after June 2021 (78%, 95%CI: 65%-86%) compared with earlier period (56%, 95%CI: 54%-59%). Subgroup meta-analysis also revealed that women and participants without underlying medical condition (chronic diseases) were significantly less likely to accept the COVID-19 vaccine, compared to men and those with medical conditions, respectively.

CONCLUSION

The study emphasizes the need for targeted public health interventions aimed at increasing vaccine acceptance among PEH, especially at the early stage of the pandemic, among females, those without underlying medical conditions, being Black (in Canada and the USA), and young people. These interventions should address the common concerns of vaccine safety, adverse effects, effectiveness, and distrust in health care systems. In addition to offering vaccinations in different areas convenient to them, education programs could be established to increase vaccine acceptance among PEH.

Strategies to improve vaccination rates in people who are homeless: A systematic review

People who are homeless experience higher rates of vaccine-preventable disease, including COVID-19, than the general population, and poorer associated health outcomes. However, delivering vaccinations to people who are homeless is complex, and there is a lack of evidence to inform practice in this area. The aim of this systematic review is to: (a) identify, (b) analyse the characteristics of, and (c) evaluate the outcomes of, strategies to improve vaccination rates in people who are homeless. Literature was retrieved from eight electronic databases. Studies undertaken in high-income countries, published in English, in a peer-reviewed journal, and in full-text were considered. No limits were placed on study design or date. A total of 1,508 articles were retrieved and, after the removal of duplicates, 637 were screened. Twenty-three articles, reporting on nineteen separate vaccination strategies for hepatitis A/B, influenza, herpes zoster, invasive pneumococcal disease, and diphtheria in people who are homeless, were selected for inclusion. All the strategies were effective at improving vaccination rates in, people who are homeless. Most strategies involved vaccination clinics and most were delivered, at least in part, by nurses. Other characteristics of successful strategies included: delivering vaccinations at convenient locations; using accelerated vaccination schedules (if available); vaccinating at the first appointment, regardless of whether a person's vaccination history or serological status were known (if clinically safe); operating for a longer duration; offering training to staff about working with people who are homeless; widely promoting clinics; considering education, reminders, incentives, and co-interventions; ensuring no out-of-pocket costs; and working collaboratively with stakeholders, including people who are homeless themselves. These findings will inform evidence-based vaccination strategies, including for COVID-19, in people who are homeless, and improve associated health outcomes in this at-risk, hard-to-reach group.

Homelessness and Hepatitis A-San Diego County, 2016-2018

BACKGROUND

Hepatitis A is a vaccine-preventable viral disease transmitted by the fecal-oral route. During 2016-2018, the County of San Diego investigated an outbreak of hepatitis A infections primarily among people experiencing homelessness (PEH) to identify risk factors and support control measures. At the time of the outbreak, homelessness was not recognized as an independent risk factor for the disease.

METHODS

We tested the association between homelessness and infection with hepatitis A virus (HAV) using a test-negative study design comparing patients with laboratory-confirmed hepatitis A with control subjects who tested negative for HAV infection. We assessed risk factors for severe hepatitis A disease outcomes, including hospitalization and death, using multivariable logistic regression. We measured the frequency of indications for hepatitis A vaccination according to Advisory Committee on Immunization Practices (ACIP) guidelines.

RESULTS

Among 589 outbreak-associated cases reported, 291 (49%) occurred among PEH. Compared with those who were not homeless, PEH had 3.3 (95% confidence interval [CI], 1.5-7.9) times higher odds of HAV infection, 2.5 (95% CI, 1.7-3.9) times higher odds of hospitalization, and 3.9 (95% CI, 1.1-16.9) times higher odds of death associated with hepatitis A. Among PEH, 212 (73%) patients recorded other ACIP indications for hepatitis A vaccination.

CONCLUSIONS

PEH were at higher risk of infection with HAV and of severe hepatitis A disease outcomes compared with those not experiencing homelessness. Approximately one-fourth of PEH had no other ACIP indication for hepatitis A vaccination. These findings support the recent ACIP recommendation to add homelessness as an indication for hepatitis A vaccination.

Adherence to hepatitis A and hepatitis B multi-dose vaccination schedules among adults in the United Kingdom: a retrospective cohort study

BACKGROUND

Timely and complete vaccination with multi-dose schedules is of public health importance, because an incomplete vaccination series may yield suboptimal disease protection. However, data on adherence of adults to multi-dose vaccines are limited. We sought to estimate adherence to multi-dose hepatitis vaccination schedules among adults in the United Kingdom (UK).

METHODS

This retrospective cohort study was conducted using anonymized electronic health record (EHR) data from the Clinical Practice Research Datalink (CPRD). Individuals aged 19 years and older at their first identified dose of hepatitis vaccine (2009-2016) were included if they had continuous EHR data for 12 months before the first identified hepatitis A dose or for 6 months before the first identified hepatitis B or combination hepatitis A/B dose. We estimated dose and series completion for each vaccine and adherence to recommended vaccination schedules, as well as adherence within additional prespecified time periods after the first vaccine dose, with sensitivity analyses restricted to adults who had available data for up to 24 months after the first dose. Median time to series completion was estimated using Kaplan-Meier methods.

RESULTS

Mean (SD) age at initiation was 42 (16) years for hepatitis A (n = 374,881), 40 (16) years for hepatitis B (n = 71,634), and 38 (15) years for hepatitis A/B (n = 10,335). Women comprised 52 to 55% of each vaccine cohort. Overall, 42,294 adults (11%) completed the two-dose hepatitis A vaccine series within the recommended 12 months; and 15,564 (22%) and 1076 (10%) completed the three-dose hepatitis B and hepatitis A/B series, respectively, within the recommended 6 months. These percentages rose to only 23, 35, and 33%, respectively, when the follow-up periods were extended to 36 months for hepatitis A and to 30 months for hepatitis B and A/B vaccines. Median times to series completion within recommended schedules were not reached in any cohort. Sensitivity analyses supported the primary findings for the full cohorts.

CONCLUSIONS

Adherence and series completion rates for hepatitis A and B vaccines in the UK are low. Identifying, understanding, and addressing barriers to series completion for multi-dose vaccines for adults in real-world settings are needed.

The financial crisis and the expected effects on vaccinations in Europe: a literature review

Starting in 2008 several European countries experienced a financial crisis. Historically, diseases whose prevention and treatment depend highly on the continuity of healthcare re-emerge during political and financial crises. Evidence suggests that the current financial crisis has had an impact on the health and welfare of Europeans and that population health status and morbidity as well as mortality patterns may change in the coming years. At the same time decisions about expenditure for health services may impact the ability of public health providers to respond. It is expected that the current crisis will further exacerbate socioeconomic and health inequalities and novel vulnerable groups will emerge in addition to existing ones. We review the available evidence and discuss how the current crisis may have an impact on vaccine-preventable diseases and influence vaccination coverage rates in Europe.