Sustainability of humoral responses to varicella vaccine in pediatric transplant recipients following a pretransplantation immunization strategy

Vaccination in adult liver transplantation candidates and recipients

In patients with chronic liver disease and liver transplant recipients, cirrhosis-associated immune dysfunction syndrome and immunosuppressant drug regimens required to prevent graft rejection lead to a high risk of severe infections, associated with acute liver decompensation, graft loss and increased mortality. In addition to maintain their global health status, vaccination represents a major preventive measure against specific infectious risks of particular concern in this population, such as invasive pneumococcal diseases, influenza or viral hepatitis A and B. However, immunization in this setting raises several issues: i) recommended vaccination schedules rely on sparse immunogenicity data without clinical efficacy and effectiveness trials designed for this specific population; ii) dynamics of immunosuppression makes timing of immunization challenging; iii) live attenuated vaccines are contraindicated after transplantation; and iv) vaccines tolerance is poorly known in cirrhotic patients. This review outlines the rational for vaccination in adult liver transplant candidates and recipients and available data regarding immunization in this specific population.

Measles, mumps, rubella (vaccine) and varicella vaccines in pediatric liver transplant: An initial analysis of post-transplant immunity

Varicella and measles infection represents a significant source of morbidity and mortality for pediatric LT recipients. We evaluated the prevalence and correlates of post-transplant immunity in pediatric LT recipients previously immunized against measles (n = 72) and varicella (n = 67). Sixteen of seventy-two (22%) patients were measles non-immune, and 42/67 (63%) were varicella non-immune after LT. Median time from LT to titers for measles and varicella was 4.0 and 3.3 years, respectively. In the measles cohort, non-immune patients received fewer pretransplant vaccine doses (P = 0.026) and were younger at both time of vaccination (P = 0.006) and LT (P = 0.004) compared with immune patients. Upon multivariable analysis, weight > 10 kg at LT (OR 5.91, 95% CI 1.27-27.41) and technical variant graft (OR 0.07, 95% CI 0.01-0.37) were independently, significantly associated with measles immunity. In the varicella cohort, non-immune patients received fewer pretransplant vaccine doses (P = 0.028), were younger at transplant (P = 0.022), and had less time lapse between their last vaccine and transplant (P = 0.012) compared with immune patients. Upon multivariate analysis, time > 1 year from last vaccine to LT was independently, significantly associated with varicella immunity (OR 3.78, CI 1.30-11.01). This study demonstrates that non-immunity to measles and varicella is a prevalent problem after liver transplantation in children and identifies 3 unique risk factors for non-immunity in this high-risk population.

Varicella zoster virus in solid organ transplantation: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the American Society of Transplantation Infectious Diseases Community of Practice review the diagnosis, prevention, and management of varicella zoster virus (VZV) in the pre- and post-transplant period. Primary varicella is an uncommon complication post-solid-organ transplant (SOT), except among pediatric transplant patients and those seronegative for VZV. As the majority of SOT recipients are seropositive for VZV, herpes zoster (HZ) occurs frequently following SOT, particularly among recipients who are older (≥65 years of age) and those receiving more intensive immunosuppression. Transplant providers should aware of the increased risk for HZ-related complications such as dissemination, organ-specific involvement, and post-herpetic neuralgia. Treatment for localized zoster is primarily given as oral regimens, but those with more complicated presentations or those at risk for dissemination should be treated initially with IV therapy. Available antiviral prophylaxis regimens and vaccination strategies for varicella and HZ among these immunosuppressed patients remain a mainstay for prevention in the pre-and post-transplant periods. Finally, we discuss important approaches to addressing post-exposure prophylaxis and infection control practices for those SOT patients with documented VZV infections.

Vaccines in pediatric transplant recipients-Past, present, and future

Infections significantly impact outcomes for solid organ and hematopoietic stem cell transplantation in children. Vaccine-preventable diseases contribute to morbidity and mortality in both early and late posttransplant time periods. Several infectious diseases and transplantation societies have published recommendations and guidelines that address immunization in adult and pediatric transplant recipients. In many cases, pediatric-specific studies are limited in size or quality, leading to recommendations being based on adult data or mixed adult-pediatric studies. We therefore review the current state of evidence for selected immunizations in pediatric transplant recipients and highlight areas for future investigation. Specific attention is given to studies that enrolled only children.

Vaccination titres pre- and post-transplant in paediatric renal transplant recipients and the impact of immunosuppressive therapy

BACKGROUND

Avoidance of vaccine-preventable infections in paediatric renal allograft recipients is of utmost importance. However, the development and maintenance of protective vaccination titres may be impaired in this patient population owing to their need for immunosuppressive medication.

METHODS

In the framework of the Cooperative European Paediatric Renal Transplant Initiative (CERTAIN), we therefore performed a multi-centre, multi-national study and analysed vaccination titres pre- and post-transplant in 155 patients with serial titre measurements in comparison with published data in healthy children.

RESULTS

The percentage of patients with positive vaccination titres before renal transplantation (RTx) was low, especially for diphtheria (38.5%, control 75%) and pertussis (21.3%, control 96.3%). As few as 58.1% of patients had a hepatitis B antibody (HBsAb) titre >100 IU/L before RTx. 38.1% of patients showed a vaccination titre loss post-transplant. Patients with an HBsAb titre between 10 and 100 IU/L before RTx experienced a significantly (p < 0.05) more frequent hepatitis B vaccination titre loss post-transplant than patients with an HBsAb titre >100 IU/L. The revaccination rate post-transplant was low and revaccination failed to induce positive titres in a considerable number of patients (27.3 to 83.3%). Treatment with rituximab was associated with a significantly increased risk of a vaccination titre loss post-transplant (odds ratio 4.26, p = 0.033).

CONCLUSIONS

These data show a low percentage of patients with positive vaccination titres pre-transplant, a low revaccination rate post-transplant with limited antibody response, and a high rate of vaccination titre losses.

Prevention and treatment of infectious complications after solid organ transplantation in children

Effective prevention, diagnosis, and treatment of infectious diseases after transplantation are key factors contributing to the success of organ transplantation. Most transplant patients experience different kinds of infections during the first year after transplantation. Children are at particular risk of developing some types of infections by virtue of lack of immunity although they may be at risk for other types due the effect of immunosuppressive regimens necessary to prevent rejection. Direct consequences of infections result in syndromes such as mononucleosis, pneumonia, gastroenteritis, hepatitis, among other entities. Indirect consequences are mediated through cytokines, chemokines, and growth factors elaborated by the transplant recipient in response to microbial replication and invasion, which contribute to the net state of immunosuppression among other effects. This review summarizes the major infections that occur after pediatric organ transplantation, highlighting the current treatment and prevention strategies, based on the available data and/or consensus.