Interventions to Increase Completion of Hepatitis B Vaccination in People who Inject Drugs: A Systematic Review and Meta-analysis

Vaccination coverage among people who inject drugs: A systematic review

BACKGROUND

People who inject drugs may be at excess risk of acquiring vaccine-preventable diseases and negative associated health outcomes, but experience barriers to vaccination. We aimed to determine vaccination coverage among people who inject drugs globally.

METHODOLOGY

We conducted systematic searches of the peer-reviewed and grey literature, date limited from January 2008 to August 2023, focusing on diseases for which people who inject drugs are at elevated risk for and for which an adult vaccination dose is recommended (COVID-19, hepatitis A, hepatitis B, human papillomavirus, influenza, pneumococcal disease, tetanus). To summarise available data, we conducted a narrative synthesis.

RESULTS

We included 78 studies/reports comprising 117 estimates of vaccination coverage across 36 countries. Most estimates were obtained from high income countries (80%, n=94). We located estimates for hepatitis B vaccination in 33 countries, which included 18 countries with data on serological evidence of vaccine-derived hepatitis B immunity (range: 6-53%) and 22 countries with self-report data for vaccine uptake (<1-96%). Data for other vaccines were scarcer: reported hepatitis A vaccination coverage ranged 3-89% (five countries), COVID-19 ranged 4-84% (five countries), while we located estimates from fewer than five countries for influenza, tetanus, pneumococcal disease, and human papillomavirus.

CONCLUSION

Estimates were sparse but where available indicative of suboptimal vaccination coverage among people who inject drugs. Improving the consistency, timeliness, and geographic coverage of vaccine uptake data among this population is essential to inform efforts to increase uptake.

Dismantling Barriers to Hepatitis B and Delta Screening, Prevention, and Linkage to Care among the PWUD Community in Philadelphia

The prevalence of hepatitis B and delta viruses (HBV/HDV) among people who use drugs (PWUD) remains largely unknown. In the context of one Philadelphia-based harm reduction organization (HRO), this study aimed to assess HBV/HDV prevalence and facilitate linkage to care. Participants completed a demographic HBV/HDV risk factor survey and were screened for HBV and reflexively for HDV if positive for HBV surface antigen or isolated core antibody. Fisher's exact tests and regression were used to understand relationships between risks and HBV blood markers. Of the 498 participants, 126 (25.3%) did not have hepatitis B immunity, 52.6% had been vaccinated against HBV, and 17.9% had recovered from a past infection. Eleven (2.2%) participants tested positive for isolated HBV core antibody, 10 (2.0%) for HBV surface antigen, and one (0.2%) for HDV antibody. History of incarceration was associated with current HBV infection, while transactional sex and experience of homelessness were predictive of previous exposure. This study found high rates of current and past HBV infection, and a 10% HBV/HDV co-infection rate. Despite availability of vaccine, one quarter of participants remained vulnerable to infection. Findings demonstrate the need to improve low-threshold HBV/HDV screening, vaccination, and linkage to care among PWUD. The study also identified gaps in the HBV/HDV care cascade, including lack of point-of-care diagnostics and lack of support for HROs to provide HBV services.

How nurses contribute to the elimination of hepatitis B? A systematic review and meta-analysis

BACKGROUND

With approximately one-third of the global population exhibiting serological evidence of exposure, the hepatitis B virus remains a serious public health threat. Elimination of hepatitis B faces enormous challenges, from prevention to diagnosis, treatment, and long-term monitoring. Nurses are pivotal in optimising the hepatitis B care continuum; however, their contributions have been neglected.

OBJECTIVE

To identify the role of nurses in the elimination of hepatitis B and to synthesise the effectiveness of interventions with nursing roles in approaching the elimination target.

DESIGN

A systematic review and meta-analysis.

SETTING(S)

Thirteen databases (EMBASE, MEDLINE via OvidSP, Ovid Emcare, Ovid Nursing Database, British Nursing Index, APA PsycINFO, Cochrane Central Register of Controlled Trials, CINAHL, Scopus, Web of Science Core Collection, China National Knowledge Internet, SinoMed, and Wanfang Data) were searched from their inception to 6 December 2022.

METHODS

Interventional studies examining the contribution of nursing roles towards elimination targets were included. Content analysis was used to extract and map the nursing roles based on the nursing interventions classification system. Random-effects meta-analyses were conducted to examine the effectiveness of the intervention in improving hepatitis B screening, detection, and vaccination rates.

RESULTS

The synthesis from 16 studies identified 13 nursing roles that primarily involved (1) health education and counselling for informed patient decision-making regarding hepatitis B prevention, vaccination, screening, and disease monitoring; (2) case management and health promotion to advocate elimination services at multiple levels and enable equitable access among marginalised communities; and (3) running specialist clinics to lead advanced practices in prescribing and carrying diagnostic tests, formulating evidence-based individualised care plans, and coordinating care throughout the disease process. Interventions with these roles achieved pooled hepatitis B screening and detection rates of 64 % (95 % confidence interval [CI] = 0.44, 0.84) and 2 % (95 % CI = 0.00, 0.05), respectively, increased the odds of hepatitis B virus vaccination by 2.61 times (95 % CI = 1.60, 4.28), improved immunity rate, and enhanced patient adherence to antiviral treatment and monitoring of liver comorbidities. However, their effects on hepatitis B virus DNA-negative conversion rates and hepatocellular carcinoma incidence were not significant.

CONCLUSIONS

Nurses play multifaceted roles in advocating hepatitis B screening and vaccination, initiating outreach efforts in marginalised communities, and leading advanced practices that effectively contribute to the elimination of hepatitis B. Policymakers should consider how nurses may help the achievement of the elimination target.

REGISTRATION

PROSPERO (CRD42022380719) registered on December 12, 2022.

TWEETABLE ABSTRACT

Nurses raised awareness, initiated outreach efforts, addressed inequalities, and led advanced practices-effectively contributing to eliminating hepatitis B.

Opiate maintenance patients' attitudes and self-reported adherence to protective measures against SARS-CoV-2 infections

Background

During the COVID-19 pandemic we assessed to which extent patients in opioid maintenance treatment (OMT) adhere to official recommendations regarding preventive intervention strategies against COVID-19.

Methods

Patients enrolled in two OMT clinics in Germany were interviewed applying a standardized questionnaire, which covered socio-demographic information, recent psychotropic substance use, recent social activities, the history of SARS-CoV-2 infection, attitudes toward official protection recommendations, and levels of adherence to these suggestions. Current mental and medical diagnoses were retrieved from medical files. In subjects without known infection and without vaccination, blood samples were tested for the identification of anti-SARS-CoV-2-S-antibodies. Interviews were performed between the end of May and the end of September 2021.

Results

Patients' (n = 155) average age was 47 years; 74% were males. In addition to the opiate dependence, in nearly 80% of cases another medical disorder was recorded. The range of medical factors that predispose for severe COVID-19 outcomes were present in 39% of patients; 18% of the sample refused to be vaccinated. Nearly all patients reported having carried out a range of activities outside their residence during the week prior to the interviews, including visits of treatment facilities (86.5%; 95% confidence interval [80.2%; 91.0%]) or meeting with friends (64.5% [65.7-71.6%]). Despite the fact that only about 47.1% [39.2%; 55%] felt well informed about measures against infection, adherence to COVID-19 countermeasures was generally high: 83.9% [77.3; 88.8%] claimed to have worn face masks always/nearly always; social distancing was performed always/nearly always by 58.7% [50.8%; 66.2%]; and hand hygiene was conducted by 64.5% [56.7%; 71.6%] of participants. None out of n = 25 tests from unvaccinated subjects was positive for anti-SARS-CoV-2-S-antibodies. Psychiatric comorbidity and educational degree were not statistically significantly associated with attitudes and compliance, except that patients with lower education felt relatively worse informed.

Conclusion

Self-reported adherence to recommended non-therapeutic intervention strategies and vaccination rates were similar to the German general population. Provision of more health-related information tailored to OMT patients appears necessary.

Preliminary Efficacy of a Theory-Informed Intervention to Increase COVID-19 Testing Uptake Among People Who Inject Drugs in San Diego County: Findings From a Pilot Randomized Controlled Trial

BACKGROUND

People who inject drugs (PWID) have low rates of COVID-19 testing yet are vulnerable to severe disease. In partnership with a mobile syringe service program (SSP) in San Diego County, CA, we developed the evidence-, community-, and Social Cognitive Theory-informed "LinkUP" intervention (tailored education, motivational interviewing, problem-solving, and planning) to increase COVID-19 testing uptake among PWID.

PURPOSE

To assess preliminary efficacy of LinkUP in increasing PWID COVID-19 testing in a pilot randomized controlled trial (RCT).

METHODS

We referred participants (PWID, ≥18 years old, San Diego County residents who had not recently undergone voluntary COVID-19 testing) to mobile SSP sites that had been randomized (by week) to offer the active LinkUP intervention or didactic attention-control conditions delivered by trained peer counselors. Following either condition, counselors offered on-site rapid COVID-19 antigen testing. Analyses estimated preliminary intervention efficacy and explored potential moderation.

RESULTS

Among 150 participants, median age was 40.5 years, 33.3% identified as Hispanic/Latinx, 64.7% were male, 73.3% were experiencing homelessness, and 44.7% had prior mandatory COVID-19 testing. The LinkUP intervention was significantly associated with higher COVID-19 testing uptake (p < .0001). Homelessness moderated intervention effects; LinkUP increased COVID-19 testing uptake more among participants experiencing homelessness (adjusted risk ratio [aRR]: 1.80; 95% CI: 1.56-2.09; p < .0001) than those not experiencing homelessness (aRR: 1.20; 95% CI: 1.01-1.43; p = .04).

CONCLUSIONS

Findings from this pilot RCT support the preliminary efficacy of the "LinkUP" intervention to increase COVID-19 testing among PWID and underscore the importance of academic-community partnerships and prevention service delivery through SSPs and other community-based organizations serving vulnerable populations.

Associations between the prevalence of chronic hepatitis B among people who inject drugs and country-level characteristics: An ecological analysis

INTRODUCTION

Globally, hepatitis B virus (HBV) is a leading cause of liver disease. People who inject drugs (PWID) are at greater risk than the general population of contracting HBV. This risk could depend on societal factors in different countries. We investigated the associations between country-level chronic HBV prevalence in PWID with national indicators of development and prevalence of HIV and hepatitis C virus (HCV).

METHODS

We used global systematic review data on chronic HBV prevalence (hepatitis B surface antigen-positive) among PWID and country-level sociodemographic characteristics from online databases. National random-effects meta-analysis estimates of HBV prevalence were the outcome in linear regression models testing for associations with country-level characteristics.

RESULTS

The study included 131,710 PWID from 304 estimates in 55 countries: the pooled HBV prevalence among PWID in the countries analysed was 4.5% (95% CI 3.9-5.1), the highest regional pooled prevalence was in East and Southeast Asia (17.6% [13.3-22.3]), and the lowest was in Western Europe (1.7% [1.4-2.1]). In multivariable models, no indicators of development were associated with HBV prevalence, but there was evidence of positive associations between HBV prevalence in the general population and among PWID, and evidence of HIV and HCV prevalence in PWID being associated with HBV prevalence in PWID: multivariable coefficients 0.03 (95% CI 0.01-0.04); p < 0.001, and 0.01 (95% CI 0.00-0.03); p = 0.01, respectively.

DISCUSSION AND CONCLUSIONS

HBV prevalence among PWID was associated with HIV and HCV prevalence among PWID and background HBV prevalence in the general population, highlighting the need for improving harm reduction in PWID and implementation of HBV vaccination, especially where HBV is endemic.

COVID-19 vaccine attitudes and facilitators among people in Australia who inject drugs

INTRODUCTION

We aimed to describe COVID-19 vaccination attitudes and identify potential facilitators for vaccine uptake among people who inject drugs.

METHODS

People who inject drugs were recruited from all eight Australian capital cities (N = 884; 65% male, mean age 44 years) and interviewed face-to-face or via telephone in June-July 2021. COVID-19 and broader vaccination attitudes were used to model latent classes. Correlates of class membership were assessed through multinomial logistic regression. Probability of endorsing potential vaccination facilitators were reported by class.

RESULTS

Three classes of participants were identified: 'vaccine acceptant' (39%), 'vaccine hesitant' (34%) and 'vaccine resistant' (27%). Those in the hesitant and resistant groups were younger, more likely to be unstably housed and less likely to have received the current season influenza vaccine than the acceptant group. In addition, hesitant participants were less likely to report a chronic medical condition than acceptant participants. Compared to vaccine acceptant and hesitant participants, vaccine-resistant participants were more likely to predominantly inject methamphetamine and to inject drugs more frequently in the past month. Both vaccine-hesitant and resistant participants endorsed financial incentives for vaccination and hesitant participants also endorsed facilitators related to vaccine trust.

DISCUSSION AND CONCLUSION

People who inject drugs who are unstably housed or predominantly inject methamphetamine are subgroups that require targeted interventions to increase COVID-19 vaccination uptake. Vaccine-hesitant people may benefit from interventions that build trust in vaccine safety and utility. Financial incentives may improve vaccine uptake among both hesitant and resistant people.

Strategies to increase the intention to get vaccinated against COVID-19: Findings from a nationally representative survey of US adults, October 2020 to October 2021

OBJECTIVES

We examined COVID-19 vaccination status, intention, and hesitancy and the effects of five strategies to increase the willingness of unvaccinated adults (≥18 years) to get a COVID vaccine.

METHODS

Online surveys were conducted between October 1-17, 2020 (N = 14,946), December 4-16, 2020 (N = 15,229), April 8-22, 2021 (N = 14,557), June 17-July 6, 2021 (N = 30,857), and September 3-October 4, 2021 (N = 33,088) with an internet-based, non-probability opt-in sample of U.S. adults matching demographic quotas. Respondents were asked about current COVID-19 vaccination status, intention and hesitancy to get vaccinated, and reasons for vaccine hesitancy. Unvaccinated respondents were assigned to treatment groups to test the effect of five strategies (endorsements, changing social restrictions, financial incentives, vaccine requirements for certain activities, and vaccine requirements for work). Chi-square tests of independence were performed to detect differences in the response distributions.

RESULTS

Willingness to be vaccinated (defined as being vaccinated or planning to be) increased over time from 47.6 % in October 2020 to 81.1 % in October 2021. By October 2021, across most demographic groups, over 75 % of survey respondents had been or planned to be vaccinated. In terms of strategies: (1) endorsements had no positive effect, (2) relaxing the need for masks and social distancing increased Intention to Get Vaccinated (IGV) by 6.4 % (p < 0.01), (3) offering financial incentives increased the IGV between 12.3 and 18.9 % (p <.001), (4) vaccine requirements for attending sporting events or traveling increased IGV by 7.8 % and 9.1 %, respectively (p = 0.02), and vaccine requirement for work increased IGV by 35.4 %. The leading causes (not mutually exclusive) for hesitancy were concerns regarding vaccine safety (52.5 %) or side effects (51.6 %), trust in the government's motives (41.0 %), and concerns about vaccine effectiveness (37.6 %).

CONCLUSIONS

These findings suggest that multiple strategies may be effective and needed to increase COVID-19 vaccination among hesitant adults during the pandemic.

Use of financial incentives to increase adult vaccination coverage: A narrative review of lessons learned from COVID-19 and other adult vaccination efforts

To encourage COVID-19 vaccination, governments have offered a wide range of incentives to their populations ranging from cash to cows. Often these programs were rolled out at scale before assessing potential effectiveness. To inform future policy, we conducted a narrative review to understand the evidence base informing these programs and the extent to which they are effective. While we found evidence on cash transfers increasing both the coverage and intention to be vaccinated for COVID-19 and other adult vaccines, improvements in coverage were limited. With mixed evidence, lottery programs did not appear to have a consistent meaningful impact on vaccination for COVID-19, and no evidence was identified on the positive effects of other non-cash incentives for COVID-19 or other adult vaccines. We conclude that the impact of cash transfers in incentivizing adult vaccination is marginal and their effectiveness in addressing vaccine hesitancy remains inconclusive.

Analysis of S gene characteristic sequences and changes in properties of protein expression in HBV ASCs with low-level HBsAg

Objective

We detected the serum HBsAg immune complex (HBsAg-CIC) and sequenced the HBV S gene in these patients to reveal the association between sustained low-level expression of HBsAg and mutated S gene sequence characteristics, protein function changes, and HBsAg immune complex formation.

Methods

A total of 204 samples were collected and divided into high-level (n = 60, HBsAg level >10 IU/ml) and low-level (n = 144, HBsAg level ≤ 10 IU/ml) HBsAg groups. The clinical and epidemiological data of the two groups were statistically compared. According to different serological patterns and genotypes, the HBsAg-CIC results of the high-level and low-level HBsAg groups were divided into different subgroups, and then the HBsAg-CIC positive rates among different subgroups were compared. We sequenced the S gene of HBV from the two groups and identified the relevant mutations in the MHR of the S gene. In addition, we compared the changes in HBsAg protein properties and functions after hot spot mutation in the MHR of the S gene.

Results

Comparing the positive rates of HBsAg-CIC under different serological patterns and genotypes in the two groups, the HBsAg-CIC positive rate was higher in the low-level HBsAg group. Moreover, there was weak correlation between HBsAg-CIC and HBsAg or HBV DNA in both groups (r = 0.32, 0.27, 0.41, 0.48; P < 0.05). Sequencing of S gene in the two groups, showed that the hot-spot mutations were T126A, M133L/T/S, and F134L/T/I in MHR of S gene of genotype B, and hot-spot mutations were Q101R and I126S/T in MHR of S gene of genotype C. Additionally, the positive rate of MHR mutation in the S gene from HBsAg-CIC positive patients was higher in the low-level HBsAg group.

Conclusion

The host immune process of clearing HBV seems to have multiple site mutations in MHR, which changes the physicochemical properties and functions of HBsAg and intensifies the formation of HBsAg-CIC, thus avoiding the effective recognition of HBsAg by the host and resulting in immune tolerance between the host and HBV, which may be one of the formation mechanisms of sustained low-level expression of HBsAg in the serum of HBV-infected persons.

Supporting syringe services programs in the initiation and scale-up of vaccine administration: findings from in-depth interviews

Background

Vaccine-hesitant persons who inject drugs are at increased risk for several vaccine-preventable diseases. However, vaccination rates among this population remain low. While syringe services programs (SSPs) are places where persons who inject drugs feel comfortable accessing services, few offer vaccination services. This study describes facilitators and barriers to vaccination at SSPs.

Methods

We used convenience sampling to conduct semi-structured, qualitative in-depth interviews with 21 SSPs in the USA from June to August 2021. Interview questions asked SSPs about their perceptions, priorities, barriers, facilitators, and the effects of partnerships and policies on vaccine administration. We used deductive thematic analysis to identify the main themes.

Results

Eight (n = 8) SSPs offered vaccinations, and thirteen (n = 13) did not offer vaccinations. Most SSPs believed offering vaccination services was important, although addressing SSP participants’ immediate needs often took precedence. Staffing, physical space, and logistical issues were the most common barriers to vaccine administration reported by SSPs, followed by SSP participant-related barriers. Facilitators of vaccine administration included access to a tracking system, partnering with agencies or other organizations providing vaccines, and having a licensed vaccination provider on-site. Partnerships provided SSPs opportunities to expand capacity but could also restrict how SSPs operate. Recommended policy changes to facilitate vaccine administration included subsidizing the cost of vaccinations and addressing restrictions around who could administer vaccinations.

Conclusions

Increasing the availability of vaccination services at SSPs requires addressing the varying capacity needs of SSPs, such as tracking systems, licensed vaccinators, and free or low-cost vaccination supplies. While these needs can be met through partnerships and supportive policies, both must consider and reflect cultural competence around the lived experiences of persons who inject drugs.

COVID-19 Vaccine Acceptability and Financial Incentives among Unhoused People in Los Angeles County: a Three-Stage Field Survey

Unhoused people have higher COVID-19 mortality and lower vaccine uptake than housed community members. Understanding vaccine hesitancy among unhoused people is key for developing programs that address their unique needs. A three-round, rapid, field-based survey was conducted to describe attitudes toward COVID-19 vaccination. Round 1 assessed vaccine brand preference, round 2 assessed intention to accept a financial incentive for vaccination, and round 3 measured vaccine uptake and assessed reasons for vaccine readiness during implementation of a financial incentive program. A total of 5177 individuals were approached at COVID-19 vaccination events for unhoused people in Los Angeles County from May through November 2021. Analyses included 4949 individuals: 3636 (73.5%) unsheltered and 1313 (26.5%) sheltered. Per self-report, 2008 (40.6%) were already vaccinated, 1732 (35%) wanted to get vaccinated, 359 (7.3%) were not yet ready, and 850 (17.2%) did not want to get vaccinated. Brand preference was evenly split among participants (Moderna 31.0%, J&J 35.5%, either 33.5%, p = 0.74). Interest in a financial incentive differed between those who were not yet ready and those who did not want to get vaccinated (43.2% vs. 16.2%, p < 0.01). After implementing a financial incentive program, 97.4% of participants who indicated interest in vaccination were vaccinated that day; the financial incentive was the most cited reason for vaccine readiness (n = 731, 56%). This study demonstrated the utility of an iterative, field-based assessment for program implementation during the rapidly evolving pandemic. Personal engagement, a variety of brand choices, and financial incentives could be important for improving vaccine uptake among unhoused people.

How Vaccine Ambivalence Can Lead People Who Inject Drugs to Decline COVID-19 Vaccination and Ways This Can Be Addressed: Qualitative Study

BACKGROUND

People who inject drugs are disproportionately impacted by SARS-CoV-2 and COVID-19, yet they do not frequently accept vaccination against SARS-CoV-2 when offered.

OBJECTIVE

This study aimed to explore why people who inject drugs decline free vaccines against SARS-CoV-2 and how barriers to vaccination can potentially be addressed.

METHODS

We conducted semistructured qualitative interviews with 17 unvaccinated adult persons who inject drugs during August and September 2021 at a New York City syringe service program, where approximately three-fourth of participants identified as Latino (55%) or African American (22%). Interviews lasted roughly 20 minutes. The interview guide examined reasons for declining vaccination, participants' understanding of COVID-19 risks, and how messages could be developed to encourage vaccine uptake among people who inject drugs.

RESULTS

Participants acknowledged that they faced increased risk from SARS-CoV-2 owing to their injection drug use but feared that long-term substance use may have weakened their health, making them especially vulnerable to side effects. Fears of possible side effects, compounded by widespread medical mistrust and questions about the overall value of vaccination contributed to marked ambivalence among our sample. The desire to protect children and older family members emerged as key potential facilitators of vaccination.

CONCLUSIONS

Community-developed messages are needed in outreach efforts to explain the importance of vaccination, including the far greater dangers of COVID-19 compared to possible unintended side effects. Messages that emphasize vaccines' ability to prevent inadvertently infecting loved ones, may help increase uptake. Community-focused messaging strategies, such as those used to increase HIV and hepatitis C virus testing and overdose prevention among people who inject drugs, may prove similarly effective.

Contingency Management and SARS-CoV-2 Testing Among People Who Inject Drugs

OBJECTIVES

People who inject drugs (PWID) are especially vulnerable to morbidity and mortality as a result of SARS-CoV-2 infection because of social and physical health vulnerabilities. Routine testing for SARS-CoV-2 is critical to reduce transmission. Contingency management-the provision of tangible rewards to reinforce positive behavior-can promote the use of health services among PWID. Evidence is scarce on the utility of contingency management to promote SARS-CoV-2 testing. The objective of this study was to evaluate the effectiveness of contingency management to increase testing among PWID.

METHODS

SARS-CoV-2 testing was implemented at 9 syringe exchange program sites in partnership with an Oregon-based nonprofit organization for 5 weeks without contingency management and for 6 weeks with contingency management (a $10 financial incentive for testing) from February 1 through mid-April 2021. We measured rates of testing among syringe exchange program clients before and after implementation of contingency management.

RESULTS

Before contingency management, SARS-CoV-2 testing occurred during approximately 131 of 1410 (9.3%) client encounters, and 123 of 997 (12.3%) unique clients were tested. During contingency management, testing occurred during approximately 571 of 1756 (32.5%) client encounters, and 407 of 1151 (35.4%) unique clients were tested. Rates of testing increased from 0.04 (SD, 0.04) before contingency management implementation to 0.25 (SD, 0.15) after implementation (t₈ = -3.88; P = .005; Cohen d = 1.46).

CONCLUSIONS

Contingency management facilitated uptake of SARS-CoV-2 testing among PWID. Contingency management may be an effective strategy for improving communicable disease testing beyond testing for SARS-CoV-2 and for improving vaccine uptake among PWID and warrants additional research.

Cash incentives, ethics, and COVID-19 vaccination

[Figure: see text].

Looking to the empirical literature on the potential for financial incentives to enhance adherence with COVID-19 vaccination

COVID-19 vaccination efforts are underway offering hope for saving lives and eliminating the pandemic. The most promising vaccines require two injections separated 3-4 weeks apart. To achieve heard immunity, 70-90% of the population or perhaps more must be inoculated. Anticipation of adherence challenges has generated commentaries on strategies to enhance adherence including financial incentives. A notable gap in these commentaries is any discussion of the scientific evidence regarding the efficacy of financial incentives for increasing vaccine adherence. This commentary addresses that gap. There is a body of controlled trials on incentivizing vaccine adherence, mostly to the hepatitis B virus (HBV) vaccine among injection drug users (IDUs). Prevalence of HBV infection is increasing as part of the opioid addiction crisis. The HBV vaccine entails a three-dose regimen (typically 0, 1, and 6 months) which has created adherence challenges among IDUs. Systematic literature reviews document significant benefit of financial incentives. For example, a 2019 meta-analysis (Tressler & Bhandari, 2019) examined 11 controlled trials examining HBV-vaccine adherence strategies, including financial incentives, accelerated dosing schedules, and case-management/enhanced services. Financial incentives were most effective resulting in a 7-fold increase in adherence to the vaccination regimen relative to no financial incentives (OR, 7.01; 95% CI, 2.88-17.06). Additional reviews provide further support for the efficacy of financial incentives for promoting adherence with vaccination (HBV & influenza). Overall, this literature suggests that financial incentives could be helpful in promoting the high levels of adherence to COVID-19 vaccines that experts project will be necessary for herd immunity.