Varicella vaccination in children with chronic renal failure. A report of the Southwest Pediatric Nephrology Study Group

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.

Long-term study showed that vaccination protected paediatric renal transplant recipients from life-threatening varicella zoster virus

AIM

Renal transplant patients are particularly susceptible to highly contagious diseases due to their reduced immunity. We studied transplant recipients to gauge their varicella zoster virus (VZV) serology status over time and the outcome of any VZV infections.

METHOD

This retrospective study comprised 85 children who underwent renal transplants in Gothenburg, Sweden, from 1986 to 2014, at a mean age of eight (1-18) years. The children's medical records were reviewed and 47 had the VZV infection pre-transplant and 38 had been vaccinated pre-transplant. Clinical outcomes were available for 85 children and serology results for 72.

RESULTS

At transplantation, the VZV seropositivity rate was 50% in the vaccination group and 94% in the infection group and the antibody titres were significantly lower in the vaccination group (p = 0.031). During the median follow-up period of five years post-transplant, 28% of the vaccinated children and 97% of the infection group remained seropositive and the varicella infection affected eight children: one in the infection group and seven in the vaccination group. The herpes zoster was observed in two children in the infection group.

CONCLUSION

This study demonstrated that VZV vaccination protected from symptomatic infections to a lesser extent than natural infection, but provided effective protection from life-threatening disease.

Vaccinations in children on immunosuppressive medications for renal disease

Renal diseases are often treated with immunosuppressive medications, placing patients at risk of infections, some of which are vaccine-preventable. However, in such patients vaccinations may be delayed or disregarded due to complications of the underlying disease process and challenges in its management. The decision to administer vaccines to immunosuppressed children is a risk-benefit balance as such children may have a qualitatively diminished immunological response or develop diseases caused by the vaccine pathogen. Vaccination may cause a flare-up of disease activity or provocation of graft rejection in renal transplant recipients. Moreover, it cannot be assumed that a given antibody level provides the same protection in immunosupressed children as in healthy ones. We have evaluated the safety and efficacy of licensed vaccines in children on immunosuppressive therapy and in renal transplant recipients. The limited evidence available suggests that vaccines are most effective if given early, ideally before the requirement for immunosuppressive therapy, which may require administration of accelerated vaccine courses. Once treatment with immunosuppressive drugs is started, inactivated vaccines are usually considered to be safe when the disease is quiescent, but supplemental doses may be required. In the majority of cases, live vaccines are to be avoided. All vaccines are generally contraindicated within 3-6 months of a renal transplant.

Travel vaccination recommendations and endemic infection risks in solid organ transplantation recipients

BACKGROUND

Solid organ transplant (SOT) recipients are often heavily immunosuppressed and consequently at risk of serious illness from vaccine preventable viral and bacterial infections or with endemic fungal and parasitic infections. We review the literature to provide guidance regarding the timing and appropriateness of vaccination and pathogen avoidance related to the immunological status of SOT recipients.

METHODS

A PUBMED search ([Vaccination OR vaccine] AND/OR ["specific vaccine"] AND/OR [immunology OR immune response OR cytokine OR T lymphocyte] AND transplant was performed. A review of the literature was performed in order to develop recommendations on vaccination for SOT recipients travelling to high-risk destinations.

RESULTS

Whilst immunological failure of vaccination in SOT is primarily the result of impaired B-cell responses, the role of T-cells in vaccine failure and success remains unknown. Vaccination should be initiated at least 4 weeks prior to SOT or more than 6 months post-SOT. Avoidance of live vaccination is generally recommended, although some live vaccines may be considered in the specific situations (e.g. yellow fever). The practicing physician requires a detailed understanding of region-specific endemic pathogen risks.

CONCLUSIONS

We provide a vaccination and endemic pathogen guide for physicians and travel clinics involved in the care of SOT recipients. In addition, recommendations based on timing of anticipated immunological recovery and available evidence regarding vaccine immunogenicity in SOT recipients are provided to help guide pre-travel consultations.

Zoster vaccination is associated with a reduction of zoster in elderly patients with chronic kidney disease

Background

Growing epidemiological evidence demonstrates increased zoster risks in people with chronic kidney disease (CKD). Study objectives were to determine zoster vaccine effectiveness in individuals with CKD in pragmatic use.

Methods

A population-based cohort study was undertaken in a 5% random sample of US Medicare from 2007 to 2009 involving 766 330 eligible individuals aged ≥65 years who were (29 785) and were not (736 545) exposed to the zoster vaccine. Incidence rates for zoster in vaccinated and unvaccinated individuals and hazard ratios for zoster comparing vaccinated with unvaccinated were determined for individuals with CKD. Time-updated Cox proportional hazards models were used, adjusting for relevant confounders.

Results

CKD was present in 183 762 (24%) of individuals (15% of vaccinees). Adjusted vaccine effectiveness [95% confidence intervals (CIs)] in individuals with CKD was 0.49 (0.36–0.65). The adjusted vaccine effectiveness in participants with both CKD and diabetes mellitus was 0.46 (95% CI 0.09–0.68). Vaccine effectiveness estimates were similar to those previously reported for the general population [vaccine effectiveness 0.48 (95% CI 0.39–0.56)].

Conclusions

Zoster vaccine is effective against incident zoster in older individuals with CKD. Extra efforts are warranted to increase vaccine uptake in individuals with CKD given the known low uptake in these higher risk individuals.

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.

Vaccines for post-exposure prophylaxis against varicella (chickenpox) in children and adults

BACKGROUND

The prevention of varicella (chickenpox) using live attenuated varicella vaccines has been demonstrated both in randomised controlled trials (RCTs) and in population-based immunisation programmes in countries such as the United States and Australia. Many countries do not routinely immunise children against varicella and exposures continue to occur. Although the disease is often mild, complications such as secondary bacterial infection, pneumonitis and encephalitis occur in about 1% of cases, usually leading to hospitalisation. The use of varicella vaccine in persons who have recently been exposed to the varicella zoster virus has been studied as a form of post-exposure prophylaxis (PEP).

OBJECTIVES

To assess the efficacy and safety of vaccines for use as PEP for the prevention of varicella in children and adults.

SEARCH METHODS

We searched CENTRAL (2014, Issue 1), MEDLINE (1966 to March week 1, 2014), EMBASE (January 1990 to March 2014) and LILACS (1982 to March 2014). We searched for unpublished trials registered on the clinicaltrials.gov and WHO ICTRP websites.

SELECTION CRITERIA

RCTs and quasi-RCTs of varicella vaccine for PEP compared with placebo or no intervention. The outcome measures were efficacy in prevention of clinical cases and/or laboratory-confirmed clinical cases and adverse events following vaccination.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and analysed data using Review Manager software.

MAIN RESULTS

We identified three trials involving 110 healthy children who were siblings of household contacts. The included trials varied in study quality, vaccine used, length of follow-up and outcomes measured and, as such, were not suitable for meta-analysis. We identified high or unclear risk of bias in two of the three included studies. Overall, 13 out of 56 vaccine recipients (23%) developed varicella compared with 42 out of 54 placebo (or no vaccine) recipients (78%). Of the vaccine recipients who developed varicella, the majority only had mild disease (with fewer than 50 skin lesions). In the three trials, most participants received PEP within three days following exposure; too few participants were vaccinated four to five days post-exposure to ascertain the efficacy of vaccine given more than three days after exposure. No included trial reported on adverse events following immunisation.

AUTHORS' CONCLUSIONS

These small trials suggest varicella vaccine administered within three days to children following household contact with a varicella case reduces infection rates and severity of cases. We identified no RCTs for adolescents or adults. Safety was not adequately addressed.

Clinical and molecular aspects of the live attenuated Oka varicella vaccine

VZV is a ubiquitous member of the Herpesviridae family that causes varicella (chicken pox) and herpes zoster (shingles). Both manifestations can cause great morbidity and mortality and are therefore of significant economic burden. The introduction of varicella vaccination as part of childhood immunization programs has resulted in a remarkable decline in varicella incidence, and associated hospitalizations and deaths, particularly in the USA. The vaccine preparation, vOka, is a live attenuated virus produced by serial passage of a wild-type clinical isolate termed pOka in human and guinea pig cell lines. Although vOka is clinically attenuated, it can cause mild varicella, establish latency, and reactivate to cause herpes zoster. Sequence analysis has shown that vOka differs from pOka by at least 42 loci; however, not all genomes possess the novel vOka change at all positions, creating a heterogeneous population of genetically distinct haplotypes. This, together with the extreme cell-associated nature of VZV replication in cell culture and the lack of an animal model, in which the complete VZV life cycle can be replicated, has limited studies into the molecular basis for vOka attenuation. Comparative studies of vOka with pOka replication in T cells, dorsal root ganglia, and skin indicate that attenuation likely involves multiple mutations within ORF 62 and several other genes. This article presents an overview of the clinical aspects of the vaccine and current progress on understanding the molecular mechanisms that account for the clinical phenotype of reduced virulence.

Varicella encephalitis and pneumonia in a patient with end stage renal failure

We describe a patient with end stage renal failure (ESRF) on hemodialysis who was admitted to our department for primary varicella infection complicated by varicella pneumonia and encephalitis. Varicella infections results in serious morbidity and mortality in ESRF dialysis and transplant patients. Evidence published thus far suggests that live attenuated varicella vaccines are effective and safe in ESRF and renal transplant patients. Worldwide a few countries have instituted guidelines for the varicella immunisation in ESRF patients. However, in the Asia Pacific Region, it has not been widely given due to the lack of national consensus guidelines. Our case depicts that primary varicella infection can occur at any time in immunosupressed patients and thus suffer serious consequences from it. With increasing burden of chronic kidney disease, Renal Physicians and Family Physicians in the Asia Pacific Region should meet and study the epidemiological data in each individual country and decide on the consensus guidelines on how the varicella vaccination can be targeted for those at risk.

Vaccination of the immunocompromised child

The development of vaccination is a major achievement in modern medicine. However, children treated with immunosuppression may not at all, or only in part, receive routine immunization due to uncertainty of its risks and effect. There is a substantial lack of pediatric studies concerning the efficacy and safety of vaccination in this patient group. Experience from similar adult groups and children with HIV infection can be used as a model for other disease categories. With increasing knowledge of the immunologic basis of vaccination and how immunosuppressive drugs interfere with the immune system, improved vaccines could be tailored, and adequate, individualized guidelines issued.

2013 IDSA clinical practice guideline for vaccination of the immunocompromised host

An international panel of experts prepared an evidenced-based guideline for vaccination of immunocompromised adults and children. These guidelines are intended for use by primary care and subspecialty providers who care for immunocompromised patients. Evidence was often limited. Areas that warrant future investigation are highlighted.

Immunizations in children with chronic kidney disease

Children with chronic kidney disease (CKD) are at increased risk for vaccine-preventable diseases. These patients may have a reduced response to and/or reduced duration of antibody after immunization and therefore monitoring of antibody levels or titers is indicated for some vaccines. In addition, pediatric CKD patients require immunizations not routinely provided to healthy children. Unfortunately, studies in pediatric CKD patients, including those on dialysis and awaiting kidney transplantation, have demonstrated sub-optimal immunization rates. In order to minimize the risk for vaccine-preventable disease in pediatric CKD patients, it is imperative that all who care for these patients remain abreast of the recommended childhood immunization schedule, as well as alterations to this schedule required for children with CKD, including end-stage kidney disease. This article reviews recent changes to the recommended childhood immunization schedule and alterations and additions to this schedule recommended for children with CKD. Where available, data on antibody response to immunizations in children with CKD are presented.

A comparison of herpes zoster incidence across the spectrum of chronic kidney disease, dialysis and transplantation

BACKGROUND

The effect of different renal replacement therapies on the risk of developing herpes zoster in renal failure patients is unknown. We aimed to investigate the incidence of herpes zoster attack among renal failure patients who were receiving different dialysis modalities, renal transplantation (RT), or not receiving any of the above mentioned therapies yet.

METHODS

A retrospective cohort study of the national health insurance register database was conducted. This observational cohort study involved 79,581 study controls, 15,802 chronic kidney disease patients, 3,694 hemodialysis (HD) patients, 317 peritoneal dialysis (PD) patients, and 159 RT patients.

RESULTS

The RT group had the worst risk of herpes zoster (hazard ratio, HR, 8.46; 95% CI 5.85-12.2), followed by PD (HR 3.61; 95% CI 2.49-4.83) and HD (HR 1.35; 95% CI 1.18-1.55), compared with the comparison group (p < 0.0001). The RT group had also the highest risk of developing herpes zoster with complications among all groups (adjusted HR 15.3). The HRs of the PD group were higher than the HRs of the HD group in terms of herpes zoster or its complications (p < 0.0001 and p = 0.0002, respectively).

CONCLUSIONS

This study suggests that different treatment modalities are associated with different risks of herpes zoster attacks in renal failure patients. PD patients had higher risks than the HD group in terms of herpes zoster or its complications.

Varicella vaccination in children with inflammatory bowel disease receiving immunosuppressive therapy

Children with inflammatory bowel disease (IBD) are often receiving chronic immunosuppressive therapy to stay in clinical remission; however, these therapies also put patients at risk for infections. Therefore, it is important to immunize children to minimize vaccine-preventable infections. However, there is a paucity of data on immune response to vaccines in patients with IBD. Current guidelines recommend that patients with IBD receive inactivated vaccines but suggest against immunizing immunosuppressed patients having IBD with live vaccines such as varicella. Unfortunately, the recommendation to not vaccinate with varicella was not based on any data. We present a case series of children with IBD receiving immunosuppressive therapy who tolerated and had a good immune response to varicella vaccine. We also review the literature and demonstrate that studies in other immunocompromised populations suggest that varicella vaccine is generally well tolerated and immunogenic. We also argue that it is important to weigh the benefits against risks with individual patients having IBD to decide whether varicella vaccination should be considered. Additional studies evaluating the safety and immunogenicity of varicella vaccine in patients with IBD are needed.

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

Varicella infections pose serious challenges for organ transplant recipients. To determine the safety and immunogenicity of the OMVV and determine the maintenance of OMVV responses in transplanted subjects at varying periods of immunosuppression within the first two yr following transplantation. Eligible subjects given a two-dose OMVV pretransplantation were monitored for AE. Antibody levels were assessed at baseline, six wk post-OMVV, pretransplantation and up to 24 months post-transplantation. Seroprotection was defined as >or=5 gpEU. Twenty-one seronegative children were vaccinated. Following 42 doses, no vaccine-related serious AE occurred. Mab_titer were 17.8 (5.7-910.2) and 183.5 EU (18.8-8116.4) at six and 12 wk, respectively (p < 0.0001). Fourteen (66.7%) participants were transplanted at a median of 16 months (1.5-56) following OMVV and had Mab_titer of 27.2 EU (9.0-236.2) just prior to transplantation. Of 11 who had post-transplantation serology, seroprotection was sustained at three, six and 12 months post-transplantation in 10/11, 12/12 and 8/10 subjects. In five of six subjects with two-yr follow-up, antibody levels remained seroprotective. No breakthrough varicella infections occurred. The receipt of OMVV prior to transplantation induced humoral responses which persisted in the early months following transplantation and up to two yr post-transplantation and was not associated with any serious adverse consequences.

Vaccines for post-exposure prophylaxis against varicella (chickenpox) in children and adults

BACKGROUND

Live attenuated varicella vaccines for the prevention of varicella (chickenpox) has been demonstrated both in randomised controlled trials (RCTs) and in population-based immunisation programmes in countries such as the United States. However, many countries do not routinely immunise children against varicella, and exposures continue to occur. Although the disease is often mild, complications such as secondary bacterial infection, pneumonitis and encephalitis occur in about 1% of cases, usually leading to hospitalisation. The use of varicella vaccine in persons who have recently been exposed to the varicella zoster virus has been studied as a form of post-exposure prophylaxis (PEP).

OBJECTIVES

To assess the efficacy and safety of vaccines for use as PEP for the prevention of varicella in children and adults.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2008, Issue 1); MEDLINE (1966 to February 2008); and EMBASE (January 1990 to February 2008).

SELECTION CRITERIA

RCTs and quasi-RCTs of varicella vaccine for PEP compared with placebo or no intervention. The outcome measures were efficacy in prevention of clinical cases and/or laboratory-confirmed clinical cases and adverse effects following vaccination.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted and analysed data using Review Manager software.

MAIN RESULTS

Three studies involving 110 healthy children who were siblings of household contacts were identified as suitable for inclusion. The studies varied in quality, study design, vaccine used, and outcomes measured and, as such, were not suitable for meta-analysis. Overall, 13 out of 56 vaccine recipients (18%) developed varicella compared with 42 out of 54 placebo (or no vaccine) recipients (78%). Of the vaccine recipients who developed varicella, the majority only had mild disease (with less than 50 skin lesions). In the three studies, most subjects received PEP within three days following exposure; too few subjects were vaccinated four to five days post exposure to ascertain the efficacy of vaccine given more than three days after exposure. No included studies reported on adverse events following immunisation.

AUTHORS' CONCLUSIONS

These small trials suggest varicella vaccine administered within three days to children following household contact with a varicella case reduces infection rates and severity of cases. No RCTs for adolescents or adults were identified. However safety was not adequately addressed.

Varicella vaccination of immunocompromised children

BACKGROUND

Exposure of immunocompromised children to varicella often requires postexposure prophylaxis. Exposures requiring this management are often not recognized. Varicella can be a severe disease when it occurs in immunocompromised children, in spite of antiviral therapy. Varicella exposure and varicella in these children can also disrupt scheduled therapy for their underlying illness. Both postexposure prophylaxis and treatment of varicella are likely to be expensive and use significant medical resources. Numerous trials have been undertaken to vaccinate children who are immunocompromised by a variety of conditions and therapies that depress their immune function.

METHODS

Clinical trials of varicella vaccine administration to immunocompromised children that were reported since 1975 were identified in the Ovid medical database. Reports were selected for analysis and discussion on the basis of their completeness and the utility of their conclusions.

RESULTS

Vaccination before immune compromise is discussed as a strategy for some settings. The obstacles, potential opportunities, and success in varicella vaccination for immunocompromised children are separately analyzed for (1) children with leukemia and other malignancies, (2) human immunodeficiency virus-infected children, and (3) children with hematopoietic stem cell or solid-organ transplantation.

CONCLUSIONS

Vaccination before immune compromise is often successful, and the vaccine-induced response is usually partially or fully protective. In many treatment settings, it is possible to safely vaccinate once the level of immune suppression has been reduced. Targets for future research are outlined. A consensus conference should be undertaken to develop guidelines for the use of varicella vaccine in immunocompromised children.

Avaliação da suscetibilidade à varicela no paciente pediátrico portador de insuficiência renal crônica

OBJETIVO: Avaliar a suscetibilidade natural à varicela de crianças e adolescentes portadores de insuficiência renal crônica (IRC). MÉTODOS: Estudo transversal de 83 pacientes com idade acima de 18 meses e inferior a 18 anos, durante 2000 e 2001, com ritmo de filtração glomerular (RFG) abaixo de 70mL/min/1,73m², portando cartão vacinal preconizado pela Fundação Nacional de Saúde e que não receberam nenhuma dose da vacina específica. Do total, três pacientes (3/83) foram excluídos, por terem recebido doses da vacina por meio de órgãos não governamentais. A sorologia foi realizada pelo método Enzyme-Linked Immuno Sorbent Assay, considerando-se títulos sorológicos protetores acima de 100mUA/mL. RESULTADOS: Os pacientes renais crônicos tinham idade mediana de 11 anos, 66% eram masculinos, 60% procedentes do próprio município de São Paulo, com RFG médio de 33,6mL/min/1,73m². O diagnóstico clínico de varicela por profissional médico ocorreu em 39 pacientes; destes, 10% se mostraram soronegativos. Dos 80 pacientes restantes, 21 (26%) apresentaram títulos não protetores para varicela. A prevalência de suscetibilidade em menores de seis anos foi 7,93 (IC95%=3,29-19,12) vezes superior à de maiores de seis anos. CONCLUSÕES: Houve diminuição da suscetibilidade à varicela com a idade. Pacientes abaixo de seis anos foram cerca de oito vezes mais suscetíveis à varicela que os renais crônicos com idade mais avançada e duas vezes mais suscetíveis do que a população pediátrica brasileira de mesma idade.

Demand for evaluation of vaccination antibody titers in children considered for renal transplantation

Vaccinations are recommended for achieving protection against vaccine-preventable infections in solid-organ transplant recipients. In order to evaluate the protection at the time of renal transplantation, the antibody titers against measles, mumps, rubella, varicella, hepatitis B, diphtheria, and tetanus were determined in 35 children one month prior to transplantation. Only 26% of patients on dialysis listed for transplantation showed protective antibodies against all tested pathogens. Particularly, low protection was found for hepatitis B. Children younger than four yr showed significantly lower protective antibody titers compared with older children for almost all vaccines. Children who completed vaccination in the last six months to six yr prior to renal transplantation showed higher rates of protective antibody titers against all pathogens compared with children who had vaccination more than six yr before transplantation. Preventive strategies in children with chronic renal failure include repeated measurements of serum antibodies and appropriate revaccination if titers decline. Our results underline the demand for continuous surveillance of specific antibody titers against vaccine-preventable diseases in the risk group of renal transplant recipients.

Overview of vaccination in chronic kidney disease

Infections are a major cause of death in end-stage renal disease (ESRD) patients, second only to cardiovascular disease, and also contribute to significant morbidity in patients with earlier stages of chronic kidney disease (CKD). Vaccines are a strategy to attempt to reduce morbidity related to infections. Patients with CKD and ESRD may not respond as well to vaccines as patients without kidney failure, but adequate seroresponse with standard or augmented regimens for vaccinations against influenza, hepatitis B, pneumococcus, and varicella have been documented. Influenza, in particular, seems to provide adequate protection with standard dosing regimens. Despite somewhat reduced effectiveness of certain vaccines in patients with CKD, there is emerging evidence of benefit to vaccination in these populations. However, vaccination rates are relatively low. Given the accumulating evidence of benefit, continuing quality improvement programs focused on increasing vaccination rates in patients with all levels of CKD are needed.

Seroprevalence of antibodies against varicella-zoster virus and response to the varicella vaccine in pediatric renal transplant patients

The severity of varicella-zoster virus (VZV) in immunocompromised children, especially in those receiving renal transplants, is well known. However, the use of live attenuated virus vaccine in this population is controversial. This study aimed to: (i) assess the immunization status of pediatric renal transplant recipients at our center; (ii) determine the anti-VZV antibody titers in such patients; (iii) evaluate the response to VZV vaccine in seronegative children and in those who present low antibody titers (defined as <500 mAU/mL). Vaccinated children were monitored for adverse effects for 8 wk after vaccination. Fifty patients with a mean age of 13.7 yr (range, 3-17 yr) were enrolled. In 49, blood samples were collected and antibodies were screened using ELISA. Seropositivity to VZV was found in 43 (88%), and antibody titers were >/=500 mAU/mL in 37 (75.5%). Of the 12 children who were eligible for vaccination and had antibody titers <500 mAU/mL, one developed varicella before vaccination, two did not meet the inclusion criteria, and three parents refused the vaccination. In the six vaccinated children, there were no adverse reactions to the vaccine, and four (66.6%) responded with anti-VZV titers >/=500 mAU/mL 6-8 wk after vaccination. In conclusion, after renal transplantation, varicella vaccine is safe with a 66% rate of conversion to high antibody titers.

Immunization in children with chronic renal failure: a practical approach

The prevention of systemic viral and bacterial infections by effective vaccination represents an essential task of pediatric nephrologists caring for children with chronic renal failure (CRF) undergoing renal transplantation (RTPL) with life-long immunosuppression. This review addresses three issues: risk of vaccine-preventable diseases, safety, immunogenicity, and clinical efficacy of available vaccines, and implementation of immunization guidelines. Infections (including vaccine-preventable infections) represent the leading cause of morbidity and mortality in children on dialysis and after RTPL. Vaccination in children with CRF and after RTPL is safe and does not cause reactivation of an immune-related renal disease or rejection after RTPL. Children with CRF generally produce protective serum antibodies to primary vaccinations with killed or component vaccines and live virus vaccines; some children on dialysis and after RTPL may not respond optimally, requiring repeated vaccination. Proof of vaccine efficacy is absence of disease, which can only be confirmed in large cohort studies. A few observational studies provide evidence that vaccination has contributed significantly, at least in the western hemisphere, to the low prevalence of vaccine-preventable diseases among children with CRF. Close cooperation between the local pediatrician/practitioner and the pediatric nephrologist is essential for successful implementation of the vaccination schedule.

A review of the varicella vaccine in immunocompromised individuals

BACKGROUND

Individuals with underlying cell-mediated immunodeficiency disorders are at high risk of developing severe, life-threatening illness associated with varicella-zoster virus infection. A live-attenuated varicella vaccine is recommended for routine childhood immunisation in some countries. In healthy children, the vaccine is efficacious and safe but because immunocompromised individuals may be unable to limit replication of live-attenuated vaccine viruses, the varicella vaccine is not recommended for them and there are few exceptions.

OBJECTIVES

The purpose of this paper is to review the published studies addressing the use of the varicella vaccine in people with cell-mediated immunodeficiency disorders.

METHODS

A computerised search on the PubMed database was used to collect the relevant papers published up to March 2003.

RESULTS

The varicella vaccine has been extensively studied in susceptible children with acute lymphoblastic leukaemia in remission, but studies involving individuals with other immunodeficiency disorders are scarce. Some of the current recommendations are based on very few and small studies with short follow-up. Immunocompromised individuals should be given the varicella vaccine only with complete knowledge of their clinical and immunological conditions and after considering the risks of natural infection and vaccination.