Varicella-zoster immunization in pediatric liver transplant recipients: safe and immunogenic.

Varicella can have a severe course in immunosuppressed patients. Although prevention is fundamental, live-attenuated varicella-zoster (VZV) vaccine is not currently recommended in transplant recipients. Our aims were to (1) evaluate VZV immunity in pediatric liver transplant (LT) recipients; (2) immunize (two doses) seronegative patients post-LT; (3) monitor vaccine safety, (4) assess B and T cell vaccine responses. All patients followed at the Swiss National Pediatric LT Center were approached and 77/79 (97.5%) were enrolled (median age 7.8 years). Vaccine safety was monitored by standardized diary cards and phone calls. VZV-specific serology and CD4(+) T cells were assessed before and after immunization. Thirty-nine patients (51.1%) were seronegative including 14 children immunized pre-LT. Thirty-six of 39 seronegative patients were immunized post-LT (median 3.0 years post LT). Local (54.8%) and systemic (64.5%) reactions were mild and transient. The frequency of VZV-specific CD4(+) T cells and antibody titers increased significantly (respectively from 0.085% to 0.16%, p = 0.04 and 21.0 to 1134.5 IU/L, p < 0.001). All children reached seroprotective titers and 31/32 (97%) patients assessed remained seroprotected at follow-up (median 1.7 years). No breakthrough disease was reported during follow-up (median 4.1 years). Thereby, VZV vaccine appears to be safe, immunogenic and provide protection against disease in pediatric LT patients.

Pneumococcal vaccines for children: a global public health priority.

Pneumococcal conjugated vaccines have been recommended in children for over a decade in many countries worldwide. Here we review the development of pneumococcal vaccines with a focus on the two types currently available for children and their safety record. We discuss also the effect of vaccines, including the 13-valent pneumococcal conjugate vaccine, on invasive pneumococcal diseases in children, particularly bacteraemia, pneumonia and meningitis, as well as on mucosal disease and carriage. In regions where immunization was implemented in young children, the number of invasive pneumococcal diseases decreased significantly, not only in the target age group, but also in younger and much older subjects. Challenges and future perspectives regarding the development of new 'universal' vaccines, which could bypass the current problem of serotype-specific protection in a context of serotype replacement, are also discussed.