H1N1 Vaccination in Pediatric Renal Transplant Patients

Kinetics of antibody response to influenza vaccination in renal transplant recipients

Annual vaccination is routinely used in organ transplant recipients for immunization against seasonal influenza. However, detailed analysis of the kinetics of vaccine-induced immune responses in this population is lacking. In this study, we investigated the kinetics of vaccine strains-specific antibody responses to trivalent influenza vaccine in a group of renal transplant recipients and a control group. First, we found that the geometric mean hemagglutination inhibition titer against all 3 vaccine strains in the transplant cohort was significantly low when compared to control subjects. Next, whereas the control group sera showed significantly higher HA-specific IgG and isotype IgG1 antibodies at all four time points, a similar increase in the transplant group was delayed until day 28. Interestingly, within the transplant group, subjects receiving belatacept/MMF/prednisone-based regimen had significantly lower levels of total IgG and HA-specific IgG when compared to tacrolimus/MMF/prednisone-based regimen. Even though IgG-ASC response in both cohorts peaked at day 7 post-vaccination, the frequency of IgG-ASC was significantly low in the transplant group. Taken together, our studies show delayed kinetics and lower levels of influenza vaccine-specific antibody responses in renal transplant recipients and, more importantly, indicate the need to probe and improve current vaccination strategies in renal transplant recipients.

Immunogenicity of the meningococcal polysaccharide conjugate vaccine in pediatric kidney transplant patients

BACKGROUND

Immunosuppressed kidney transplant patients may have suboptimal response to vaccinations. The aim of this study was to determine antibody response to a quadrivalent meningococcal conjugate vaccine (MenACWY-D) in adolescents with a kidney transplant.

METHODS

This was a prospective, single-center, cohort study. Adolescent patients (11-22 years old) with a functioning kidney transplant for at least 3 months and no previous meningococcal vaccination were eligible for enrollment. Antibody levels to all serogroups were measured before vaccination (baseline) and at 4 weeks and 1, 2 and 3 years after vaccination. Seropositivity was defined as a titer ≥ 1:8 at baseline, and seroconversion as a fourfold or greater increase in antibody titer from baseline at 4 weeks post-vaccination. Geometric mean titers (GMTs) were calculated at each time point and compared to published GMTs from vaccinated healthy adolescents.

RESULTS

Nineteen patients were enrolled. No patient had seroprotective titers against all four serogroups at baseline. At 4 weeks post-vaccination 41% of patients seroconverted to all four serogroups, with seroconversion rates of 88, 53, 71 and 94% for serogroups A, C, W and Y, respectively. GMTs were significantly lower in adolescents with a kidney transplant than in healthy adolescents at 1 month (p = 0.02) and 3 years (p = 0.04) post-vaccination. There were no significant adverse events, episodes of rejection or death in any patient.

CONCLUSIONS

Adolescents with a kidney transplant may not respond adequately to MenACWY-D and may experience more rapid declines in antibody titers than healthy adolescents. Further study is needed to determine if alternative dosing schedules can improve antibody response in this population.

Vaccine administration in children with chronic kidney disease

Pediatric patients with severe chronic kidney disease (CKD) on conservative treatment, on dialysis, and those with renal transplantation are at a higher risk for infectious diseases as the result of impaired immune responses against infectious agents. Infections in these patients can have drastic consequences for disease morbidity and mortality. Immunization is a crucial preventive strategy for disease management in this pediatric population. However, vaccination coverage among children with CKD remains low due to safety concerns and doubts about vaccine immunogenicity and efficacy. In this study, we reviewed why children with CKD are at higher risk of infections, the importance of vaccinations among these children, barriers to vaccinations, and recommend the best vaccination schedules. Overall, vaccines have acceptable immunogenicity, efficacy, and safety profiles in children with CKD. However, in some cases, the protective antibody levels induced by vaccines and the benefits and risks of booster vaccine doses must be individually managed. Furthermore, close contacts and household members of these children should complete age-appropriate vaccination schedules to increase the child's indirect protection.

Immunogenicity of pandemic influenza A H1N1/2009 adjuvanted vaccine in pediatric solid organ transplant recipients

The aim of this study was to assess the immunogenicity of a vaccine against this virus in a prospective cohort of transplanted pediatric patients without previous influenza infection who received one dose of MF59®-adjuvanted pandemic H1N1/2009 vaccine. Seventeen patients who were being regularly followed up at the Outpatient Clinic of the Children's Transplant Unit (liver and kidney transplantation) in Hospital Universitari Vall d'Hebron (Barcelona) were included. Seroconversion was demonstrated in 15 of 17 (88.2%) vaccinated children. There were no rejection episodes or major adverse events. The MF59(®) -adjuvanted pandemic H1N1/2009 vaccine was safe and elicited an adequate response.

Respiratory viral infections in pediatric solid organ and hematopoietic stem cell transplantation

Respiratory viruses are common in children, including pediatric recipients of both solid organ transplantation and hematopoietic stem cell transplantation. The prevalence and risk factors in each of these groups are reviewed. Furthermore, associated morbidity and mortality in pediatric transplant recipients with respiratory viral infections are addressed. The literature on specific prevention and treatment options for respiratory syncytial virus, adenovirus, influenza, and other respiratory viruses in pediatric solid organ and hematopoietic stem cell transplant recipients is reported.

Safety of pandemic H1N1 vaccines in children and adolescents

During the 2009 influenza A (H1N1) pandemic several pandemic H1N1 vaccines were licensed using fast track procedures, with relatively limited data on the safety in children and adolescents. Different extensive safety monitoring efforts were put in place to ensure timely detection of adverse events following immunization. These combined efforts have generated large amounts of data on the safety of the different pandemic H1N1 vaccines, also in children and adolescents. In this overview we shortly summarize the safety experience with seasonal influenza vaccines as a background and focus on the clinical and post marketing safety data of the pandemic H1N1 vaccines in children. We identified 25 different clinical studies including 10,505 children and adolescents, both healthy and with underlying medical conditions, between the ages of 6 months and 23 years. In addition, large monitoring efforts have resulted in large amounts of data, with almost 13,000 individual case reports in children and adolescents to the WHO. However, the diversity in methods and data presentation in clinical study publications and publications of spontaneous reports hampered the analysis of safety of the different vaccines. As a result, relatively little has been learned on the comparative safety of these pandemic H1N1 vaccines - particularly in children. It should be a collective effort to give added value to the enormous work going into the individual studies by adhering to available guidelines for the collection, analysis, and presentation of vaccine safety data in clinical studies and to guidance for the clinical investigation of medicinal products in the pediatric population. Importantly the pandemic has brought us the beginning of an infrastructure for collaborative vaccine safety studies in the EU, USA and globally.