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

Measles vaccination in lung transplant candidates

Background

The incidence of measles is now increasing. Measles is especially dangerous for high-risk individuals, including lung transplant candidates with severe progressive bronchopulmonary disorders.

Objective

The objective of this study was to investigate how vaccine-induced immunity is developed in lung transplant candidates seronegative for measles. In order to study vaccine-induced measles immunity, the study subjects were divided in two groups. The main group consisted of 22 patients (11 males and 11 females) with severe bronchopulmonary disorders, aged 19 to 58. The control group was made up of healthcare providers who were matched with respect to age and gender to the patients in the main group. All study subjects were given a single dose of measles vaccine. Levels of anti-measles IgG antibodies (Ab) were measured by enzyme-linked immunosorbent assay (ELISA) using the VectoMeasles-IgG kit (Russia).

Results

One month after vaccination, both study groups showed a statistically significant increase in anti-measles IgG Ab compared to baseline levels. In the main group, vaccine-induced Ab levels were significantly lower than in the control group (0.41 [0.098; 1.75] IU/mL vs. 1.94 [0.96; 3.3] IU/mL; р<0.0001). The rates of seroconversion were 73% and 100% in the main and control groups, respectively. The majority of non-responders (83%) in the main group had restrictive pulmonary disease. One year after vaccination, anti-measles Ab were detected in 36% (5/14) of the patients in the main group.

Conclusion

Administration of a single dose of measles vaccine to seronegative lung transplant candidates with severe progressive bronchopulmonary disorders was safe and resulted in protective levels of antibodies in 73% of patients. One year after vaccination, anti-measles Ab were detected in 36% of the patients, which suggested that a single dose failed to induce a robust immune response in this patient population.

No Vaccine, No Organ? Ethics of Vaccine Mandates for Pediatric Transplant

Many transplant programs worldwide are likely to impose vaccine mandates for pediatric solid organ transplant candidates; some already do. Three potential benefits that advocates invoke to justify mandates are improved patient outcomes, efficient organ allocation, and contributions to community protection. We show that none of these benefits can justify mandates. The medical benefits of mandates are unlikely to outweigh the risks of denying life-saving care, mandates threaten trust and equity in organ allocation, and the impact on community protection is likely negligible, while the burden on unvaccinated children would be disproportionate. We also reject the claim that clinician burdens in dealing with vaccine refusers are good reasons for mandates, and point out, to the contrary, that the potential political backlash to mandates is a good reason for restraint. Rather, we argue that vaccine mandates for pediatric transplant candidates should be a last resort; they should only be considered after all evidence-based noncoercive measures have been exhausted, and after mandates for transplant professionals and staff are in place. Since there is little evidence that all such measures have been attempted, it is premature to consider vaccine mandates.

Post-Transplantation Seroprotection Rates in Liver, Lung, and Heart Transplant Recipients Vaccinated Pre-Transplantation against Hepatitis B Virus and Invasive Pneumococcal Disease

Vaccination before solid organ transplantation is recommended since post-transplantation immunosuppression is known to impair vaccine responses. However, little is known about post-transplantation seroprotection rates in organ transplant recipients vaccinated pre-transplantation. We aimed to investigate the proportion of transplant recipients vaccinated against hepatitis B virus (HBV) and invasive pneumococcal disease (IPD) pre-transplantation at the time of listing for transplantation with post-transplantation seroprotection. We included 136 solid organ transplant (SOT) recipients vaccinated at the time of listing for transplantation. We investigated post-transplantation antibody concentrations against HBV and IPD. Established antibody thresholds were used to define seroprotection. The proportions of SOT recipients with post-transplantation seroprotection were 27.9% (n = 38) and 42.6% (n = 58) against HBV and IPD, respectively. Compared to completing HBV vaccination pre-transplantation, completing post-transplantation vaccination (adjusted odds ratio (aOR): 7.8, 95% CI: 2.5-24.5, p < 0.001) and incomplete vaccination (aOR: 6.3, 95% CI: 1.2-32.6, p = 0.028) were associated with non-response against HBV, after adjustment for confounders. Importantly, patients with seroprotection at the time of listing had lower odds of non-response against HBV (aOR: 0.04, 95% CI: 0.0-0.1, p < 0.001) and IPD (aOR: 0.3, 95% CI: 0.1-0.7, p = 0.007) compared to those without seroprotection. SOT recipients vaccinated pre-transplantation had low post-transplantation seroprotection rates against HBV and IPD. However, SOT recipients with seroprotection at the time of listing had lower odds of non-response, suggesting early vaccination should be a priority.

The changing landscape of infections in the lung transplant recipient

PURPOSE OF REVIEW

Infections in lung transplant recipients remain a major challenge and can affect lung allograft function and cause significant morbidity and mortality. New strategies for the prevention and treatment of infection in lung transplantation have emerged and are reviewed.

RECENT FINDINGS

For important vaccine preventable infections (VPIs), guidance has been updated for at risk solid organ transplant (SOT) recipients. However, data on the efficacy of newer vaccines in lung transplant, including the respiratory syncytial virus (RSV) vaccine, are limited. Studies demonstrate improved vaccination rate with Infectious Diseases consultation during pretransplant evaluation. Two new antiviral agents for the treatment and prevention of cytomegalovirus (CMV) in SOT, letermovir and maribavir, are being incorporated into clinical care. CMV-specific cell-mediated immune function assays are more widely available. Antibiotics for the management of multidrug resistant pathogens and Burkholderia cepacia complex have been described in case series and case reports in lung transplant.

SUMMARY

Although new vaccines and novel therapies for preventing and treating infections are available, larger studies evaluating efficacy in lung transplant recipients are needed.

Characteristics of Anti-Measles Immunity in Lung Transplant Candidates

Measles has not yet been eradicated; therefore, its outbreaks are still reported throughout the world. Like any infection, measles is dangerous for immunocompromised patients. Levels of anti-measles IgG antibodies were measured in 157 patients aged 17 to 72, who were placed on the lung transplant waiting list. Measurements were undertaken by enzyme-linked immunosorbent assay (ELISA) using the VectoMeasles-IgG kit (Russia). The proportion of patients seronegative for measles was 19% (30/157). Correlation was detected between patients' age and their levels of anti-measles antibodies, with higher proportions of patients having undetectable titers (25.5-28.9%) or low antibody levels (38.3-44.4%) in the young age groups (17-29 and 30-39 years old). There were no differences between male and female patients in levels of anti-measles antibodies or in the proportion of seronegative individuals. Analyses of antibody levels with regard to type of disease revealed the highest rate of seronegative results in cystic fibrosis patients (34.4%, 11/32). Overall, 19% of lung transplant candidates, mostly young people and cystic fibrosis patients, did not have protective immunity against measles.

Mycophenolate Interruption Restores Anti-SARS-CoV-2 Vaccine Immunogenicity in Unresponsive Liver Transplant Recipients

BACKGROUND & AIMS

The fourth dose of anti-SARS-CoV-2 vaccine slightly improved the humoral response among previously seronegative liver transplant (LT) recipients. Mycophenolate (MMF) treatment worsens the vaccination response. This study aimed to evaluate whether temporary MMF interruption might improve the immunogenicity of the fourth anti-SARS-CoV-2 BNT16b2 vaccine dose in nonresponsive LT recipients.

METHODS

LT recipients negative for anti-spike glycoprotein-specific immunoglobulin G receptor-binding domain (s-RBD) antibodies after the third vaccine dose were enrolled. Anti-SARS-CoV-2 spike-specific T-cell responses were measured before and 2 months following the fourth vaccine dose, and anti-SARS-CoV-2 s-RBD antibodies also 6 months thereafter. MMF was suspended two weeks before and after vaccination.

RESULTS

Five LT recipients were enrolled. After a mean of 78 days after vaccination, all patients tested positive for anti-SARS-CoV-2 s-RBD antibodies. The mean antibody titer was 8944 UI/mL. The positive antibody response was maintained during a mean of 193 days of follow-up. Three patients developed a positive T-cell response. Two patients (one positive for T-cell response) developed a self-limited SARS-CoV-2 infection.

CONCLUSIONS

Suspending MMF prior to the fourth dose of the anti-SARS-CoV-2 mRNA vaccine seems feasible and safe. This procedure could restore vaccine-induced immunogenicity in a large portion of previously nonresponsive LT recipients.