Underimmunization of the solid organ transplant population: An urgent problem with potential digital health solutions

Incomplete Immunity for Varicella and Measles in Pediatric Organ Transplant Candidates. Real World Experience From an Infectious Diseases Pre-Transplantation Clinic

BACKGROUND

Vaccinating pediatric solid organ transplant candidates against measles and varicella is crucial due to the risk of severe disease in immunosuppressed recipients and general avoidance of live virus vaccines post-transplantation. The world saw a resurgence of measles starting 2012 prompting the American Society of Transplantation in 2015 to release guidelines on recognition, prevention, and post-exposure prophylaxis of this disease in solid transplant recipients. This study aims to assess the extent of incomplete immunity to these viruses in candidates and the approach to immunity optimization during a period of heightened awareness.

METHODS

A cross-sectional study from 2012 to 2016 at Cleveland Clinic Children's included pediatric solid organ transplant candidates. Data on vaccination history, serology, and demographics were collected. Incomplete immunity was defined by incomplete vaccination or seronegativity.

RESULTS

Among 91 candidates, 54.9% had complete varicella vaccination. Serological varicella immunity among patients tested varied by age: < 7 years, 50.0% positive in patients with complete schedules, none in the incomplete; ≥ 7 years, 50.0% positive in patients with complete schedules, 65.5% in the incomplete. For measles, 69.2% had complete vaccination, with immunity varying by age among those tested: < 7 years, 84.6% positive in patients with complete schedules, 42.9% in the incomplete; ≥ 7 years, 81.0% with complete, 62.5% with incomplete. Only 31.1% of those who qualified for a varicella additional dose and 28% who qualified for an additional measles dose received it, respectively.

CONCLUSIONS

Incomplete immunity to varicella and measles was prevalent in pediatric solid organ transplant candidates at our center during the study period. Despite an increase in global measles activity, our efforts to optimize immunity through additional vaccine doses were only partially successful. Future research should focus on addressing strategies and understanding barriers to ensure timely vaccination for this vulnerable population prior to transplant, especially during periods of increased viral activity.

Vaccinations in Paediatric Solid Organ Transplant Candidates and Recipients

Solid organ transplant (SOT) candidates and recipients are a fragile population, in which the presence of a pre-transplant disease leading to organ insufficiency and the post-transplant immunosuppressive treatment expose them to an increased risk of infectious diseases. The best intervention to guarantee efficient prevention of infections, with optimal cost-benefit ratio, is represented by vaccination programs; however, the response to vaccines needs that the immune system maintains a good function. This is even more relevant at paediatric age, when specific immunological conditions make transplant candidates and recipients particularly vulnerable. Paediatric patients may be naïve to most infections and may have incomplete immunization status at the time of transplant listing due to their age. Moreover, the unaccomplished development of a mature immune system and the immunosuppressive regimen adopted after transplant might affect the efficacy of post-transplant vaccinations. Therefore, every effort should be made to obtain the widest vaccination coverage before the transplantation, whenever possible. This review reports the most relevant literature, providing information on the current approach to the vaccinations in paediatric SOT candidates and recipients.

Reasons for COVID-19 Vaccine Hesitancy Among Patients Listed for Solid Organ Transplants

BACKGROUND

Patients listed for solid organ transplants (LSOTP) are at high risk for severe COVID-19 outcomes. Despite national guidelines recommending COVID-19 vaccination for LSOTP, vaccine hesitancy and underuse are reported in this population; however, reasons for this finding have not been examined thoroughly.

METHODS

This single-center retrospective survey analysis aimed to characterize reasons for COVID-19 vaccine hesitancy among 110 heart, liver, and kidney patients LSOTP who had not received all the recommended vaccine doses at the time of the study. Survey questions also investigated experiences with influenza vaccination.

RESULTS

Fifty-four patients (49.1%) responded to the telephone survey. The most common reasons for vaccine hesitancy were perceived lack of research in vaccine development (31%), fear of vaccine-related side effects (22%), and belief that the vaccine was unnecessary (20%). Of the respondents, 35% reported changing their vaccine perception after being listed for a transplant, most commonly attributing this to a perception that the COVID-19 vaccine is not safe for transplant recipients (32%). Gender differences in hesitancy reasons were observed, with males more likely to delay vaccination until after transplantation, although this difference was not significant (P = .07). Despite these findings, 54% of all respondents reported receiving annual influenza vaccines consistently.

CONCLUSION

Despite their risk, patients LSOTP show significant hesitancy toward COVID-19 vaccines owing to perceived safety and necessity issues. The results of this study can inform targeted educational efforts to address and rectify misconceptions and concerns about COVID-19 vaccination among patients LSOTP. Future studies focused on larger, more diverse cohorts are needed to expand our understanding of and address vaccination hesitancy among this vulnerable patient population.

Vaccine-Preventable Illness Leads to Adverse Outcomes in Liver Transplant Recipients

BACKGROUND

Liver transplant recipients (LTR) and patients with chronic liver disease (CLD) are at an increased risk of infections.

AIMS

The objective of our study was to assess the incidence, and impact of vaccine preventable illness (VPI) on outcomes in LTR.

METHODS

National Inpatient Sample (NIS) 2016-2020 was used to identify adults (age > 18) hospitalized LTR using ICD-10 codes. Data were collected on patient demographics, hospital characteristics, etiology of liver disease, hepatic decompensations and outcomes. Patients were stratified into two groups based on the presence or absence of VPI. Multivariate logistic regression analysis was performed to identify the association between VPI and outcomes.

RESULTS

Out of 170,650 hospitalized LTR, 13.5% of the patients had VPI. The most common VPI was noted to be influenza (10.7%), followed by pneumococcal infection (2.7%). Incidence of mortality (6.9% vs. 1.6%, p < 0.001), ICU admissions (14.3% vs. 3.4%, p < 0.001), and acute kidney injury (AKI) (43.7% vs 37.35%, p < 0.001) was higher in the VPI group.

CONCLUSION

More than 13% of the LT hospitalizations had concomitant VPI. VPI in LTR was associated with worse outcomes. Our data suggests the need to identify factors associated with reduced vaccination rates and identify strategies to improve vaccination rates and responses in these patients.

Safety and immunogenicity of the live-attenuated varicella vaccine in pediatric solid organ transplant recipients: A systematic review and meta-analysis

This study aimed to synthesize the available evidence on the immunogenicity, safety, and effectiveness of live-attenuated varicella vaccine in solid organ transplant recipients. Medline and EMBASE were searched using predefined search terms to identify relevant studies. The included articles reported varicella vaccine administration in the posttransplant period in children and adults. A pooled proportion of transplant recipients who seroconverted and who developed vaccine-strain varicella and varicella disease was generated. Eighteen articles (14 observational studies and 4 case reports) were included, reporting on 711 transplant recipients who received the varicella vaccine. The pooled proportion was 88.2% (95% confidence interval 78.0%-96.0%, 13 studies) for vaccinees who seroconverted, 0% (0%-1.2%, 13 studies) for vaccine-strain varicella, and 0.8% (0%-4.9%, 9 studies) for varicella disease. Most studies followed clinical guidelines for administering live-attenuated vaccines, with criteria that could include being at least 1 year posttransplant, 2 months postrejection episode, and on low-dose immunosuppressive medications. Varicella vaccination in transplant recipients was overall safe in the included studies, with few cases of vaccine-strain-induced varicella or vaccine failure, and although it was immunogenic, the proportion of recipients who seroconverted was lower than that seen in the general population. Our data support varicella vaccination in select pediatric solid organ transplant recipients.

Vaccination in Kidney Transplant Candidates

Background

Kidney transplant (KT) candidates have historically low immunization rates against recommended vaccines. A retrospective single-center study of contemporary KT candidates was conducted to assess vaccination rates and vaccine uptake.

Methods

All KT candidates ≥18 y evaluated between January 1, 2020, and December 31, 2020, were retrospectively reviewed for history of prior vaccination against tetanus, diphtheria, and pertussis; 13-valent pneumococcal conjugate vaccine; 23-valent pneumococcal polysaccharide vaccine; and recombinant zoster vaccine. Positive hepatitis A IgG total, hepatitis B surface antibody, measles, mumps, rubella, and varicella IgG were assessed as surrogate markers of immunity. Vaccine uptake among vaccine-eligible candidates was also assessed.

Results

Among 150 KT candidates, the rate of prior vaccination against tetanus, diphtheria, and pertussis; 13-valent pneumococcal conjugate vaccine; 23-valent pneumococcal polysaccharide vaccine; and recombinant zoster vaccine (latter among patients ≥50 y) was found to be as low as 11%. Hepatitis A IgG total, hepatitis B surface antibody, measles, mumps, rubella, and varicella IgG seropositivity rates were 30%, 66%, 88%, 78%, 90%, and 96%, respectively. Only 7 (5%) of 150 patients had complete immunization or seropositivity. Five (3%) of 143 vaccine-eligible patients declined vaccination. Hepatitis A vaccine declination was relatively common with 15 (16%) of 94 vaccine-eligible patients declining it.

Conclusions

KT candidates have low baseline rates of prior immunization/seropositivity against most recommended vaccines. Overall vaccine uptake among eligible candidates was high.

Immunization of Solid Organ Transplant Candidates and Recipients: A 2022 Update

Immunizations are a relatively safe and cost-effective intervention to prevent morbidity and mortality associated with vaccine preventable infection (VPIs). As such, immunizations are a critical part of the care of pre and posttransplant patients and should be prioritized. New tools are needed to continue to disseminate and implement the most up-to-date vaccine recommendations for the SOT population. These tools will help both primary care providers and multi-disciplinary transplant team members taking care of transplant patients to stay abreast of evidence-based best practices regarding the immunization of the SOT patient.

Vaccine-Preventable Infections Among Solid Organ Transplant Recipients in Switzerland

Importance

Vaccine responses are decreased in solid organ transplant (SOT) recipients, and given the complexity of implementation, vaccination programs may be suboptimal. The actual burden of vaccine-preventable infections (VPIs) among SOT recipients remains unclear.

Objectives

To assess the incidence rate of VPIs among SOT recipients and to evaluate whether SOT recipients are at increased risk for specific VPIs compared with the general population.

Design, Setting, and Participants

This nationwide cohort study used data from the Swiss Transplant Cohort Study on VPIs in individuals who underwent SOT from May 2008 to June 2019 (follow-up until December 2019) and data from the Swiss Federal Office of Public Health on notifiable VPIs in the general population in the same period. Data were analyzed from January 2021 to June 2022.

Exposures

Solid organ transplant.

Main Outcomes and Measures

The main outcomes were the incidence rate of the following VPIs in SOT recipients: hepatitis A and B, diphtheria, Haemophilus influenzae infection, influenza, measles, mumps, pertussis, pneumococcal disease, poliomyelitis, meningococcal disease, rubella, tetanus, tick-borne encephalitis, and varicella zoster virus infection. Age-adjusted standardized incidence ratios were used to assess whether VPIs occurred more frequently in SOT recipients compared with the general population. For SOT recipients, factors associated with occurrence of VPIs were explored and the associated morbidity and mortality assessed.

Results

Of 4967 SOT recipients enrolled (median age, 54 years [IQR, 42-62 years]; 3191 [64.2%] male), 593 (11.9%) experienced at least 1 VPI. The overall VPI incidence rate was higher in the population that underwent SOT (30.57 per 1000 person-years [PY]; 95% CI, 28.24-33.10 per 1000 PY) compared with the general population (0.71 per 1000 PY). The standardized age-adjusted incidence ratio for notifiable VPIs in SOT recipients was higher compared with the general population (27.84; 95% CI, 25.00-31.00). In SOT recipients, influenza and varicella zoster virus infection accounted for most VPI episodes (16.55 per 1000 PY [95% CI, 14.85-18.46 per 1000 PY] and 12.83 per 1000 PY [95% CI, 11.40-14.44 per 1000 PY], respectively). A total of 198 of 575 VPI episodes in the population that underwent SOT (34.4%) led to hospital admission, and the occurrence of a VPI was associated with an increased risk for death and/or graft loss (hazard ratio, 2.44; 95% CI, 1.50-3.99; P = .002). In multivariable analysis, age 65 years or older at the time of transplant (incidence rate ratio [IRR], 1.29; 95% CI, 1.02-1.62) and receipt of a lung (IRR, 1.77; 95% CI, 1.38-2.26) or a heart (IRR, 1.40; 95% CI, 1.05-1.88) transplant were associated with an increased risk of VPI occurrence.

Conclusions and Relevance

In this study, 11.9% of SOT recipients experienced VPIs, and the incidence rate was higher than in the general population. There was significant morbidity and mortality associated with these infections in the population that underwent SOT, which highlights the need for optimizing immunization strategies.

Approaches to pretransplant vaccination

PURPOSE OF REVIEW

The aim of this study was to summarize new data and perspectives in pretransplant vaccination, with a particular focus on COVID-19 vaccination and vaccination requirements.

RECENT FINDINGS

Pretransplant vaccination produces superior markers of immunity and is expected to have greater clinical benefit, compared with posttransplant vaccination. As such, efforts are underway to identify and characterize barriers to pretransplant vaccination, with a particular focus on COVID-19 vaccine hesitancy. Unfortunately, vaccine hesitancy is common in transplant patients, often motivated by individual side effect and safety concerns. COVID-19 vaccination requirements have been implemented in some centres, informed by ethical principles, including beneficence, utility and justice.

SUMMARY

Barriers to pretransplant vaccination can be understood in three categories: hard stops, including issues of vaccine availability, eligibility, safety and feasibility; soft stops, including issues of convenience, prioritization and care coordination; and volitional stops related to vaccine hesitancy and refusal. All of these barriers present opportunities for improvement based on recent data.

Organ transplant and Covid-19 vaccination: Considering the ethics of denying transplant to unvaccinated patients

Recently, a number of organ transplant centers in the United States have proposed to only allow patients who have received the Covid-19 vaccination to be active on their transplant waiting list. This raises numerous ethical issues. This analysis utilizes current empirical data and the guidelines on the ethics of organ allocation published by the Organ Procurement and Transplant Network to guide our ethical reasoning. We conclude that it would be permissible to mandate Covid-19 vaccination as a condition of being listed for an organ transplant at a transplant center and offer recommendations for how to do so.

Early humoral immune response to two doses of severe acute respiratory syndrome coronavirus 2 vaccine in a diverse group of solid organ transplant candidates and recipients

Response to two doses of a nucleoside-modified messenger ribonucleic acid (mRNA) vaccine was evaluated in a large solid-organ transplant program. mRNA COVID-19 vaccine was administered to transplant candidates and recipients who met study inclusion criteria. Qualitative anti-SARS-CoV-2 Spike Total Immunoglobulin (Ig) and IgG-specific assays, and a semi-quantitative test for anti-SARS-CoV-2 Spike protein IgG were measured in 241 (17.2%) transplant candidates and 1,163 (82.8%) transplant recipients; 55.2% of whom were non-Hispanic White and 44.8% identified as another race. Transplant recipients were a median (IQR) of 3.2 (1.1, 6.8) years from transplantation. Response differed by transplant status: 96.0% vs 43.2% by the anti-SARS-CoV-2 Total Ig (candidates vs recipients, respectively), 93.5% vs 11.6% by the anti-SARS-CoV-2 IgG assay, and 91.9% vs 30.1% by anti-spike titers after two doses of vaccine. Multivariable analysis revealed candidates had higher likelihood of response vs recipients (odds ratio [OR], 14.6; 95 %CI 2.19, 98.11; p = 0.02). A slightly lower response was demonstrated in older patients (OR 0.96; 95 %CI 0.94, 0.99; p = 0.002), patients taking antimetabolites (OR, 0.21; 95% CI 0.08, 0.51; p = 0.001). Vaccination prior to transplantation should be encouraged. This article is protected by copyright. All rights reserved.

The influence of selected factors on the immunogenicity of preventive vaccinations against hepatitis A, B and influenza in solid organ transplant recipients undergoing immunosuppressive therapy - a review

INTRODUCTION

Immunization is the most effective form of the primary prevention of infectious diseases. Knowledge on the efficacy and immunogenicity of vaccinations in the group of organ transplant patients taking chronic immunosuppressive treatment remains incomplete.

AREAS COVERED

The aim of this paper was to analyze factors influencing the post-vaccination response in patients undergoing chronic immunosuppressive therapy based on a literature review. Only publications that evaluated the immunogenicity of influenza, HAV and HBV vaccinations in patients on immunosuppressive therapy were reviewed.

EXPERT OPINION

The following methods are used to potentially increase the immunogenicity of vaccinations against HAV and HBV amongst post-transplantation patients: increasing the number of doses, increasing dose volumes, the method of administering as well as the addition of adjuvant. Immunogenicity is also impacted by the immunosuppression mechanism. Overall, vaccination has been concluded to be safe for post-transplantation patients and adverse events following immunization (AEFI) have typically been rated as mild or moderate. The instances of transplant rejections as observable in the long term have not been related to administered vaccinations. The data shows certain correlations of some factors with increased immunogenicity, however it is necessary to repeat the studies on a more representative group of patients.

A Smartphone App to Increase Immunizations in the Pediatric Solid Organ Transplant Population: Development and Initial Usability Study

Background

Vaccine-preventable infections result in significant morbidity, mortality, and costs in pediatric transplant recipients. However, at the time of transplant, less than 20% of children are up-to-date for age-appropriate immunizations that could prevent these diseases. Smartphone apps have the potential to increase immunization rates through their ability to provide vaccine education, send vaccine reminders, and facilitate communication between parents and a multidisciplinary medical group.

Objective

The aim of this study was to describe the development of a smartphone app, Immunize PediatricTransplant, to promote pretransplant immunization and to report on app functionality and usability when applied to the target population.

Methods

We used a mixed methods study design guided by the Mobile Health Agile Development and Evaluation Lifecycle. We first completed a formative research including semistructured interviews with transplant stakeholders (12 primary care physicians, 40 parents or guardians of transplant recipients, 11 transplant nurse coordinators, and 19 transplant subspecialists) to explore the acceptability of an immunization app to be used in the pretransplant period. Based on these findings, CANImmunize Inc developed the Immunize PediatricTransplant app. We next held 2 focus group discussions with 5-6 transplant stakeholders/group (n=11; 5 parents of transplant recipients, 2 primary care physicians, 2 transplant nurse coordinators, and 2 transplant subspecialists) to receive feedback on the app. After the app modifications were made, alpha testing was conducted on the functional prototype. We then implemented beta testing with 12 stakeholders (6 parents of transplant recipients, 2 primary care doctors, 2 transplant nurse coordinators, and 2 transplant subspecialists) to refine the app through an iterative process. Finally, the stakeholders completed the user version of the Mobile Application Rating Scale (uMARS) to assess the functionality and quality of the app.

Results

A new Android- and Apple-compatible app, Immunize PediatricTransplant, was developed to improve immunization delivery in the pretransplant period. The app contains information about vaccine use in the pretransplant period, houses a complete immunization record for each child, includes a communication tool for parents and care providers, and sends automated reminders to parents and care providers when immunizations are due. During usability testing, the stakeholders were able to enter a mock vaccine record containing 16 vaccines in an average of 8.1 minutes (SD 1.8) with 87% accuracy. The stakeholders rated engagement, functionality, aesthetics, and information quality of the app as 4.2/5, 4.5/5, 4.6/5, and 4.8/5, respectively. All participants reported that they would recommend this app to families and care teams with a child awaiting solid organ transplant.

Conclusions

Through a systematic, user-centered, agile, iterative approach, the Immunize PediatricTransplant app was developed to improve immunization delivery in the pretransplant period. The app tested well with end users. Further testing and agile development among patients awaiting transplant are needed to understand real-world acceptability and effectiveness in improving immunization rates in children awaiting transplant.

Live Vaccines in Pediatric Liver Transplant Recipients: "To Give or Not to Give"

Content available: Author Audio Recording.

Pre-transplant vaccination compliance in adult heart and lung transplant recipients

BACKGROUND

Vaccine preventable diseases can affect solid organ transplant recipients post-transplant. Therefore, the administration of vaccines and assessment of serologic response should be prioritized in the pre-transplant period.

METHODS

This single-center, retrospective study included 349 adult heart or lung transplant candidates between December 1, 2017 and November 30, 2019. We describe vaccination or serologic status for hepatitis A, hepatitis B, tetanus, pneumococcal, influenza, and other recommended vaccinations among heart or lung transplant candidates.

RESULTS

Eighty-two heart transplant candidates (91%) and 77 lung transplant candidates (30%) received an ID consult prior to transplant. More patients completed the pneumococcal series (66.7% vs. 28.6%, P = .045) in the heart transplant group that received an ID consult. In the lung transplant group, patients with an ID consult demonstrated higher rates of immunity to hepatitis A (84.4% vs. 72.9%, P = .047), hepatitis B (75.3% vs. 56.9%, P = .005), and measles (71.4% vs. 52.5%, P = .005) compared to those without.

CONCLUSIONS

Our results demonstrate the value of consulting ID and administering vaccinations in the early evaluation phase, prior to transplant listing. Opportunities remain to better optimize vaccination rates prior to transplant in heart and lung transplant candidates.

Incidence of herpes zoster in adult solid organ transplant recipients: A meta-analysis and comprehensive review

BACKGROUND

Chronic immunosuppressive therapy in solid organ transplant (SOT) recipients can trigger latent varicella zoster virus reactivation even in those with stable graft function. The inactivated herpes zoster (HZ) vaccine can be effective in preventing post-transplant HZ, which can cause severe neuralgia or disseminated disease. This meta-analysis aims to assess the incidences of HZ across transplant organs in SOT recipients.

METHODS

We included 12 observational studies (6560 recipients) from a PubMed and EMBASE search of articles through October 2019 and collected data from single-center dating from January 2001 to December 2017 (3498 recipients). The pooled HZ incidence and its differences between subgroups were obtained from random-effect models and meta-analysis of variance tests using R package.

RESULTS

The overall pooled crude incidence was 9.1% (95% confidence interval [CI], 7.6%-10.8%). The pooled incidence was similar between sexes but significantly different between transplanted organs (P < .001). Heart transplants (HT) (n = 644) have the highest pooled incidence with 15.2% (95% CI, 12.7%-18.2%), followed by lung transplants (LTX) (n = 780) with 11.0% (8.3%-14.4%). Kidney transplants (n = 5435) have the lowest incidence of 6.7 (5.1%-8.8%). The meta-regression analysis revealed that HZ development had a relationship with past graft rejection (P = .024).

CONCLUSION

These data support the need for subunit HZ vaccination in SOT recipients with a high risk for HZ, especially HT and LTX recipients, without respect to the late post-transplant period.

Barriers to Pretransplant Immunization: A Qualitative Interview Study of Pediatric Solid Organ Transplant Stakeholders

OBJECTIVES

To describe the experiences and beliefs of pediatric transplant stakeholders regarding factors that contribute to low pretransplant immunization rates.

STUDY DESIGN

Semistructured interviews were conducted with transplant team members (hepatologists, cardiologists, nephrologists, transplant nurse coordinators, and transplant infectious diseases physicians), primary care physicians, and parents of heart, liver, and kidney transplant recipients at 3 geographically diverse large pediatric transplant centers in the US. Interviews were conducted between July 2017 and February 2020 until thematic saturation was reached within each stakeholder subgroup. Content analysis methodology was used to identify themes.

RESULTS

Stakeholders participated in 30- to 60-minute interviews (16 transplant subspecialists, 3 transplant infectious diseases physicians, 11 transplant nurse coordinators, 12 primary care physicians, and 40 parents). Five central themes emerged: (1) gaps in knowledge about timing and safety of pretransplant immunizations, (2) lack of communication, coordination, and follow-up between team members regarding immunizations, (3) lack of centralized immunization records, (4) subspecialty clinic functioning as the medical home for transplant candidates but unable to provide all needed immunizations, and (5) differences between organ type in prioritization and completion of pretransplant immunization.

CONCLUSIONS

There are multiple factors that contribute to low immunization rates among pediatric transplant candidates. New tools are needed to overcome these barriers and increase immunization rates in transplant candidates.