Comparison of multiple immunization schedules for Haemophilus influenzae type b-conjugate and tetanus toxoid vaccines following bone marrow transplantation

Joint consensus statement on the vaccination of adult and paediatric haematopoietic stem cell transplant recipients: Prepared on behalf of the British society of blood and marrow transplantation and cellular therapy (BSBMTCT), the Children's cancer and Leukaemia Group (CCLG), and British Infection Association (BIA)

Haematopoietic stem cell transplant (HSCT) recipients have deficiencies in their adaptive immunity against vaccine preventable diseases. National and International guidance recommends that HSCT recipients are considered 'never vaccinated' and offered a comprehensive course of revaccination. This position statement aims to draw upon the current evidence base and existing guidelines, and align this with national vaccine availability and licensing considerations in order to recommend a pragmatic and standardised re-vaccination schedule for adult and paediatric HSCT recipients in the UK.

Revisiting Role of Vaccinations in Donors, Transplant Recipients, Immunocompromised Hosts, Travelers, and Household Contacts of Stem Cell Transplant Recipients

Vaccination is an effective strategy to prevent infections in immunocompromised hematopoietic stem cell transplant recipients. Pretransplant vaccination of influenza, pneumococcus, Haemophilus influenza type b, diphtheria, tetanus, and hepatitis B, both in donors and transplant recipients, produces high antibody titers in patients compared with recipient vaccination only. Because transplant recipients are immunocompromised, live vaccines should be avoided with few exceptions. Transplant recipients should get inactive vaccinations when possible to prevent infection. This includes vaccination against influenza, pneumococcus, H. influenza type b, diphtheria, tetanus, pertussis, meningococcus, measles, mumps, rubella, polio, hepatitis A, human papillomavirus, and hepatitis B. Close contacts of transplant recipients can safely get vaccinations (inactive and few live vaccines) as per their need and schedule. Transplant recipients who wish to travel may need to get vaccinated against endemic diseases that are prevalent in such areas. There is paucity of data on the role of vaccinations for patients receiving novel immunotherapy such as bispecific antibodies and chimeric antigen receptor T cells despite data on prolonged B cell depletion and higher risk of opportunistic infections.

Vaccination of haemopoietic stem cell transplant recipients: guidelines of the 2017 European Conference on Infections in Leukaemia (ECIL 7)

Infection is a main concern after haemopoietic stem cell transplantation (HSCT) and a major cause of transplant-related mortality. Some of these infections are preventable by vaccination. Most HSCT recipients lose their immunity to various pathogens as soon as the first months after transplant, irrespective of the pre-transplant donor or recipient vaccinations. Vaccination with inactivated vaccines is safe after transplantation and is an effective way to reinstate protection from various pathogens (eg, influenza virus and Streptococcus pneumoniae), especially for pathogens whose risk of infection is increased by the transplant procedure. The response to vaccines in patients with transplants is usually lower than that in healthy individuals of the same age during the first months or years after transplant, but it improves over time to become close to normal 2-3 years after the procedure. However, because immunogenic vaccines have been found to induce a response in a substantial proportion of the patients as early as 3 months after transplant, we recommend to start crucial vaccinations with inactivated vaccines from 3 months after transplant, irrespectively of whether the patient has or has not developed graft-versus-host disease (GvHD) or received immunosuppressants. Patients with GvHD have higher risk of infection and are likely to benefit from vaccination. Another challenge is to provide HSCT recipients the same level of vaccine protection as healthy individuals of the same age in a given country. The use of live attenuated vaccines should be limited to specific situations because of the risk of vaccine-induced disease.

Infectious diseases in allogeneic haematopoietic stem cell transplantation: prevention and prophylaxis strategy guidelines 2016

Infectious complications after allogeneic haematopoietic stem cell transplantation (allo-HCT) remain a clinical challenge. This is a guideline provided by the AGIHO (Infectious Diseases Working Group) of the DGHO (German Society for Hematology and Medical Oncology). A core group of experts prepared a preliminary guideline, which was discussed, reviewed, and approved by the entire working group. The guideline provides clinical recommendations for the preventive management including prophylactic treatment of viral, bacterial, parasitic, and fungal diseases. The guideline focuses on antimicrobial agents but includes recommendations on the use of vaccinations. This is the updated version of the AGHIO guideline in the field of allogeneic haematopoietic stem cell transplantation utilizing methods according to evidence-based medicine criteria.

Immunization of children with secondary immunodeficiency

The main causes of secondary immunodeficiency at a pediatric age include infectious diseases (mainly HIV infection), malignancies, haematopoietic stem cell or solid organ transplantation and autoimmune diseases. Children with secondary immunodeficiency have an increased risk of severe infectious diseases that could be prevented by adequate vaccination coverage, but vaccines administration can be associated with reduced immune response and an increased risk of adverse reactions. The immunogenicity of inactivated and recombinant vaccines is comparable to that of healthy children at the moment of vaccination, but it undergoes a progressive decline over time, and in the absence of a booster, the patients remain at risk of developing vaccine-preventable infections. However, the administration of live attenuated viral vaccines is controversial because of the risk of the activation of vaccine viruses. A specific immunization program should be administered according to the clinical and immunological status of each of these conditions to ensure a sustained immune response without any risks to the patients' health.

Evaluation of pretransplant influenza vaccination in hematopoietic SCT: a randomized prospective study

Pretransplant influenza vaccination of the donor or allogeneic hematopoietic SCT (HSCT) candidate was evaluated in a randomized study. One hundred and twenty-two HSCT recipients and their donors were assigned to three randomization groups: no pretransplant vaccination (n=38), donor pretransplant vaccination (n=44) or recipient pretransplant vaccination (n=40). Specific IgG was assessed by both hemagglutinin inhibition (HI) and, in 57 patients, by an indirect influenza-specific ELISA at specified times after HSCT. Vaccinated donors had seroprotective HI titers for Ags H1 and H3 (P<0.001) compared with the other groups at the time of donation. The titers against H1 (P=0.028) and H3 (P<0.001) were highest in the pretransplant recipient vaccination group until day 180 after transplantation. A significant difference was found in the specific Ig levels against pandemic H1N1 at 6 months after SCT (P=0.02). The mean IgG levels against pandemic H1N1 and generic H1N1 and H3N2 were highest in the pretransplant recipient vaccination group. We conclude that pretransplant recipient vaccination improved the influenza-specific seroprotection rates.

Species-specific and cross-reactive IgG1 antibody binding to viral capsid protein 1 (VP1) antigens of human rhinovirus species A, B and C

Background

Human rhinoviruses (HRV) are associated with upper and lower respiratory illnesses, including severe infections causing hospitalization in both children and adults. Although the clinical significance of HRV infections is now well established, no detailed investigation of the immune response against HRV has been performed. The purpose of this study was to assess the IgG1 antibody response to the three known HRV species, HRV-A, -B and -C in healthy subjects.

Methods

Recombinant polypeptides of viral capsid protein 1 (VP1) from two genotypes of HRV-A, -B and -C were expressed as glutathione S-transferase (GST) fusion proteins and purified by affinity and then size exclusion chromatography. The presence of secondary structures similar to the natural antigens was verified by circular dichroism analysis. Total and species-specific IgG1 measurements were quantitated by immunoassays and immunoabsorption using sera from 63 healthy adults.

Results

Most adult sera reacted with the HRV VP1 antigens, at high titres. As expected, strong cross-reactivity between HRV genotypes of the same species was found. A high degree of cross-reactivity between different HRV species was also evident, particularly between HRV-A and HRV-C. Immunoabsorption studies revealed HRV-C specific titres were markedly and significantly lower than the HRV-A and HRV-B specific titres (P<0.0001). A truncated construct of HRV-C VP1 showed greater specificity in detecting anti-HRV-C antibodies.

Conclusions

High titres of IgG1 antibody were bound by the VP1 capsid proteins of HRV-A, -B and -C, but for the majority of people, a large proportion of the antibody to HRV-C was cross-reactive, especially to HRV-A. The improved specificity found for the truncated HRV-C VP1 indicates species-specific and cross-reactive regions could be defined.

Immune responses to inhalant allergens

This overview describes the nature of the immune responses induced by the inhalation of allergens. There is a dichotomy in that B cells have multiple mechanisms that limit the amount of immunoglobulin E (IgE) antibody production, whereas T-cell responses are large even in nonallergic subjects. With the possible exception of responses to cat allergen, however, T cells from nonallergic subjects have limited effector function of helping IgG antibody, and in house-dust mite allergy, this declines with age. Regulation by interleukin 10 (IL-10)-producing cells and CD25⁺ T-regulatory cells has been proposed, but critically, there is limited evidence for this, and many studies show the highest IL-10 production by cells from allergic subjects. Recent studies have shown the importance of nonlymphoid chemokines thymic stromal lymphopoietin and IL-27, so studying responses in situ is critical. Most sources of allergens have 1 or 2 dominant allergens, and for house-dust mite, it has been shown that people have a predictable responsiveness to high-, mid-and poor-IgE-binding proteins regardless of the total size of their response. This allergen hierarchy can be used to design improved allergen preparations and to investigate how antiallergen responses are regulated.

Clinical practice implications of immunizations after pediatric bone marrow transplant: a literature review

The number of pediatric bone marrow transplants is increasing for malignant and nonmalignant diseases. The number of survivors is also increasing, and their long-term health and protection from infection is increasingly important. To prevent infections, it is standard practice to re-immunize pediatric patients after bone marrow transplant (BMT) using the Centers for Disease Control and Prevention immunization guidelines; however, surveys in the United States and other parts of the world indicate that many BMT patients do not receive all the recommended immunizations. A literature review was conducted to identify research based on evidence for immunization following BMT and to recognize barriers to the process. Also, the immunization clinical guidelines from 2000 and 2011 for patients following BMT were compared and an updated clinical protocol and immunization schedule was developed to reflect the current evidence, encourage a change in practice, and discourage fragmented care.

Immunization in special populations

In summary, immunizations in special populations require understanding the underlying disease and how it might affect the immune system's ability to mount an antibody response to vaccines or predispose certain patient populations to developing certain serious infections. There is still a great need for research on the optimal timing of vaccines after transplants, how to assess protection and development of a protective antibody response after immunization, and whether certain groups (eg, HIV) need to be revaccinated after a certain amount of time if their antibody levels decline. In addition, there are limited data on efficacy of the newer vaccines in these special patient populations, which also requires further investigation.

Foresight in medicine: current challenges with Haemophilus influenzae type b conjugate vaccines

An effective vaccine to prevent invasive infections caused by Haemophilus influenzae type b (Hib) bacteria has been available for more than 20 years. Hib conjugate vaccine is safe, efficacious and easy to use, and its cost-benefit ratio is high both in industrialized as well as in developing countries. In spite of this, WHO estimates that every year approximately 8 million children contract life-threatening Haemophilus infections, especially meningitis or severe pneumonia. If we want to take seriously the Millenium Development Goal of reducing the mortality of under 5-year-old children by two-thirds before the year 2015, an effective means to contribute to this would be more efficient use of Hib vaccines.

Vaccinations in children treated with standard-dose cancer therapy or hematopoietic stem cell transplantation

Most children with cancer are immunocompromised during therapy and for a variable period after completion of therapy. They are at an increased risk of infections, including vaccine-preventable infections. There is a reduction in immunity to vaccine-preventable diseases after completion of standard-dose chemotherapy and after hematopoietic stem cell transplant. It is important to protect these children against vaccine-preventable diseases by reimmunization.

Vaccination responses and lymphocyte subsets after autologous stem cell transplantation

Twenty autologous stem cell transplant recipients were vaccinated with three doses of Diphtheria-Tetanus-Poliomyelitis vaccine and conjugated Haemophilus influenzae type b (Hib) vaccine. Pneumococcal vaccination consisted of two doses of conjugated vaccine followed by a single dose of polysaccharide vaccine, at 6, 8 and 14 months after transplantation, respectively. Mean anti-tetanus, anti-Hib and anti-pneumococcal IgG antibodies significantly increased after each vaccination. Response rates after the full vaccination schedule were 94%, 78% and 61% for Hib, conjugated 7-valent pneumococcal vaccine and non-conjugated 23-valent pneumococcal vaccine, respectively. Three months after transplantation, CD16(+)CD56(+) NK cells were in the normal range and remained so. The total number of T lymphocytes at 3 months was and remained in the normal range. The mean CD4/CD8 ratio was 0.43 at 3 months post aSCT and, while gradually increasing, remained subnormal. The mean number of CD19(+) B lymphocytes significantly increased during the study period. Patients with CD19 counts <0.10 x 10(9)L(-1) required at least two Hib vaccinations to show a response, while the majority of patients with CD19 counts > or = 0.20 x 10(9)L(-1) showed a response to Hib after one vaccination only. Thus, a minimum threshold level of CD19(+) cells appears to be required for adequate responses to vaccination.

Development of T cell-mediated immunity after autologous stem cell transplantation: prolonged impairment of antigen-stimulated production of gamma-interferon

The conditioning regimens for autologous SCT (auto-SCT) lead to impairment of the immune system and concomitant increase in susceptibility to infections. We studied the recovery of cellular immunity by in vitro analysis of T-cell proliferation and cytokine production profiles during the first 15 months after auto-SCT in patients with multiple myeloma and non-Hodgkin's lymphoma. PBMC were collected at 6, 9 and 15 months after transplantation and stimulated with a combination of CD2 and CD28 monoclonal antibodies, with PHA or with tetanus toxoid as recall antigen. A multiplex enzyme linked immunoassay was used to determine levels of Th1 cytokines IL-2, IFN-gamma and tumour-necrosis factor-alpha (TNF-alpha), Th2 cytokines IL-4, IL-5 and IL-13, the regulatory cytokine IL-10 and the proinflammatory cytokines IL-1alpha, IL-1beta, IL-6 and the chemokine IL-8. T-cell proliferation progressively increased from 6 to 15 months after auto-SCT. Overall, cytokine production increased after auto-SCT. Production of Th2 cytokines IL-5 and IL-13 was superior to production of Th1 cytokines IFN-gamma and TNF-alpha. We hypothesize that prolonged impairment of IFN-gamma production might contribute to the relatively high incidence of viral infections after auto-SCT.

Revaccination with measles, tetanus, poliovirus, Haemophilus influenzae type B, meningococcus C, and pneumococcus vaccines in children after hematopoietic stem cell transplantation

BACKGROUND

There is a decrease in antibody levels after hematopoietic stem cell transplant (HSCT), and such patients may be at increased risk of acquiring vaccine-preventable infection. A simple and validated revaccination schedule is required. The aim of this study was to evaluate the immunogenicity of a revaccination schedule for pediatric HSCT recipients.

METHODS

Thirty-eight children (age, 1-18 years) who had undergone autologous or allogeneic HSCT for malignant diseases were recruited. All children received vaccinations in accordance with a predefined schedule. Antibody concentrations were measured before and 2-4 weeks after vaccination against tetanus; Haemophilus influenzae type b (Hib); meningococcus C; measles; poliovirus serotypes 1, 2, and 3; and 9 pneumococcus serotypes.

RESULTS

Before vaccination, protective antibody levels were found for tetanus in 95% of patients (geometric mean concentration [GMC], 0.07 IU/mL; 95% CI, 0.05-0.1 IU/mL), for Hib in 63% (GMC, 0.34 microg/mL; 95% CI, 0.21-0.57 microg/mL), for measles in 60% (GMC, 102 mIU/mL; 95% CI, 41-253 mIU/mL), for meningococcus C in 11% (geometric mean titer [GMT], 1:4; 95% CI, 1:2-1:8.4), for all 3 poliovirus serotypes in 29%, and for all 9 pneumococcal serotypes in 0%. Vaccination resulted in a significant increase (P < or = .05) in antibody levels to each vaccine antigen studied, with 100% of patients achieving protection against tetanus (GMC, 2.2 IU/mL; 95% CI, 1.8-2.7 IU/mL), 100% achieving protection against Hib (GMC, 8.4 microg/mL; 95% CI, 7.6-9.3 microg/mL), 100% achieving protection against measles (GMC, 2435 mIU/mL; 95% CI, 1724-3439 mIU/mL), 100% achieving protection against meningococcus C (GMT, 1:5706; 95% CI, 1:3510-1:9272), 92% achieving protection against the 3 poliovirus serotypes, and > or = 80% achieving protection against each of the heptavalent pneumococcal conjugate vaccine-associated serotypes. No factors relevant to age, underlying disease, or treatment type were found to significantly influence responses.

CONCLUSION

Revaccination of pediatric HSCT recipients in accordance with this revaccination schedule provides a high level of protection against these vaccine-preventable diseases.

A randomized study on donor immunization with tetanus–diphtheria, Haemophilus influenzae type b and inactivated poliovirus vaccines to improve the recipient responses to the same vaccines after allogeneic bone marrow transplantation

The HLA-identical sibling donors of 111 bone marrow transplantation (BMT) recipients were randomised to receive or not to receive tetanus-diphtheria (T-d), Haemophilus influenzae type b (Hib), and inactivated poliovirus (IPV) vaccines 2-10 weeks before BM harvest. Fifty-three (DV+ group) recipients received the graft from a vaccinated donor and 58 (DV- group) from an unvaccinated donor. All recipients were vaccinated with the T-d, Hib and IPV vaccines at 3, 6 and 12 months after BMT. Diphtheria and Hib antibody concentrations were consistently higher in the DV+ than in the DV- group from 6 months post transplantation onwards. The differences were significant at 6 and 13 months for diphtheria and at 12 months for Hib antibody concentrations. Tetanus, PV1, PV2 and PV3 antibody levels were similar in both groups. Patients transplanted from donors with high tetanus, diphtheria and Hib antibody concentrations had higher respective antibody concentrations after BMT than those transplanted from donors with low antibody concentrations. Especially patients whose donors have low-specific antibody concentrations may benefit from donor vaccination with protein and conjugate vaccines.

Immunization issues before and after solid organ transplantation in children

Solid-organ transplant recipients are at risk from various infectious diseases, many of which can be prevented by immunizations that could reduce morbidity and mortality. However, it is not uncommon for children requiring transplantation to have received inadequate or no immunizations pre-transplant. Every effort should be made to immunize transplant candidates early in the course of their disease according to recommended schedules prior to transplantation. It is also important to immunize their household contacts and healthcare workers. In this review, we summarize the major immunization issues for children undergoing transplantation, the data currently available on immunization safety and efficacy, and suggest immunization practices to reduce vaccine-preventable disease. There is a real need for a standardized approach to the administration and evaluation of immunizations in this group of patients.

Rituximab for steroid-refractory chronic graft-versus-host disease

B cells may be implicated in the pathophysiology of chronic graft-versus-host disease (GVHD), as evidenced by antibody production against sex-mismatched, Y chromosome-encoded minor HLA antigens in association with chronic GVHD. We therefore designed a phase 1/2 study of anti-B-cell therapy with rituximab in steroid-refractory chronic GVHD. Twenty-one patients were treated with 38 cycles of rituximab. Rituximab was tolerated well, and toxicity was limited to infectious events. The clinical response rate was 70%, including 2 patients with complete responses. Responses were limited to patients with cutaneous and musculoskeletal manifestations of chronic GVHD and were durable through 1 year after therapy. The median dose of prednisone among treated subjects fell from 40 mg/day to 10 mg/day, 1 year after rituximab therapy (P < .001). A chronic GVHD symptom score improved in the majority of treated patients. Antibody titers against Y chromosome-encoded minor HLA antigens fell and remained low, whereas titers against infectious antigens (EBV, tetanus) remained stable or rose during the treatment period. We conclude that specific anti-B-cell therapy with rituximab may be beneficial for patients with steroidrefractory chronic GVHD. This trial was registered at www.clinicaltrials.gov as #NCT00136396.

Reimmunization after hematopoietic stem cell transplantation

Hematopoietic stem cell transplant recipients lose immune memory of exposure to infectious agents and vaccines accumulated through a lifetime, and therefore need to be revaccinated. Reimmunization protocols vary greatly among hematopoietic stem cell transplant centers. Diphtheria and tetanus toxoids, pertussis vaccine, Haemophilus influenza type B conjugate, 23-valent pneumococcal polysaccharide, inactivated influenza and polio vaccine and live attenuated measles-mumps-rubella vaccine are the currently recommended vaccines to be included in a vaccination program after hematopoietic stem cell transplant. Other variables, such as stem cell source, new adjuvants, T-cell depleted transplants, nonmyeloablative conditioning and donor immunization have recently been introduced and a constant update of current recommendations are needed. Studies recently published, the use of other vaccines and the perspectives for different vaccination protocols are discussed in this review.

Protective antibody responses to pneumococcal conjugate vaccine after autologous hematopoietic stem cell transplantation

Patients undergoing autologous hematopoietic stem cell transplantation (autoHCT) are at increased risk for infection with Streptococcus pneumoniae and have impaired antibody responses to pneumococcal polysaccharide vaccines. We performed this study to examine the ability of autoHCT patients to respond to a heptavalent pneumococcal conjugate vaccine (PCV7) given after transplantation and to determine whether there was a potential benefit of immunizing these patients before stem cell collection. Sixty-one patients scheduled for autoHCT were randomized to receive either PCV7 or no vaccine before stem cell collection. After stem cell reinfusion, all study patients were immunized with PCV7 at 3, 6, and 12 months. Pneumococcal immunoglobulin G antibody concentrations were measured at the time of each immunization and 1 month after the 12-month dose. Serotype-specific pneumococcal antibody concentrations were significantly higher in patients immunized with PCV7 before stem cell collection compared with patients not immunized before their stem cells were collected for 6 of 7 serotypes at 3 months, 6 of 7 serotypes at 6 months, 4 of 7 serotypes at 12 months, and 3 of 7 serotypes at 13 months. After the 3-dose series of PCV7 after autoHCT, >60% of study patients had protective concentrations of antibody to all 7 vaccine serotypes regardless of immunization before stem cell collection. Pneumococcal conjugate vaccine is immunogenic in autoHCT patients and may be an effective strategy to prevent invasive disease after transplantation.

Patients undergoing treatment for pancreatic adenocarcinoma can mount an effective immune response to vaccinations

BACKGROUND

Immunotherapy has been proposed as a novel treatment for pancreatic cancer. However, patients with pancreatic cancer have been observed to have depressed immune responses, suggesting that immunotherapy might have limited utility in this group of patients. We sought to determine whether patients undergoing postresection or primary medical treatment for pancreatic adenocarcinoma were immunocompetent.

METHODS

We enrolled patients with pancreatic adenocarcinoma scheduled for postresection or primary chemotherapy and/or radiation therapy. At the initiation of therapy, the patients had an anergy panel placed and baseline blood work performed. During the first week of treatment, patients received tetanus toxoid (TT), Haemophilus influenzae and Pneumococcus vaccines. Twelve weeks after vaccine administration, IgG titers against the 3 administered vaccines were done, and lymphocyte proliferation assays in response to TT were performed.

RESULTS

Eighteen patients were originally enrolled, and 14 patients completed all elements of the trial. Anergy panel responses were obtained for 15 patients who comprised the final study group; both pre- and postvaccination data were available for 14 patients. Nine of 15 patients demonstrated at least a 10-mm induration in response to mumps or Candida antigen (60% response rate, 95% confidence interval (CI) 32-84%). Thirteen of 14 patients demonstrated a > or =3-fold increase in IgG against one or more vaccines (93% response rate, 95% CI 66-100%). Nine of 14 patients (64% response rate, 95% CI 35-87%) demonstrated at least a 3-fold rise of lymphocyte proliferation against TT.

CONCLUSIONS

Patients with pancreatic cancer were capable of mounting effective cellular and humoral responses to standard vaccines. These data suggest that immunotherapy for pancreatic cancer may be feasible and merits further investigation.

Rationale for the development of immunotherapy regimens against enterococcal infections

Enterococci are the third most common pathogen isolated in bloodstream infections. Increasing resistance against multiple antimicrobial agents has left few treatment options for enterococcal infections, and alternative therapeutic approaches are needed. Although a variety of virulence factors have been described for Enterococcus faecalis, only aggregation substance (AS) and a teichoic acid-like capsular polysaccharide have been evaluated for their potential for vaccine development. Antibodies raised against purified capsular polysaccharide are highly opsonic and protect mice against bacteremia after active and passive immunization. Since E. faecalis expresses only a limited number of capsular serotypes, this antigen may be an attractive candidate for development of a conjugate vaccine.

Immunization of children after solid organ transplantation

The array of immunizations commonly used in childhood has risen in an attempt to prevent many of the potentially serious infections of infancy and childhood. In this article, the authors provide rational guidelines for vaccination of these children. The authors briefly review the susceptibilities caused by immunosuppression in these patients, discuss the problems with various immunizations, and make individual recommendations regarding the use of each vaccine. Most recommendations are based on inferences from populations that may not be directly comparable to the transplantation population (patients with HIV or cancer or patients who have undergone bone marrow transplant), from case reports, and from small series of patients. The best recommendations ultimately must await the results of controlled trials of immunization.

Recommendations for immunizations in stem cell transplantation

Investigations over the past decade have documented that there is a decline in immunity to vaccine preventable diseases in many SCT recipients. The majority of immunization studies conducted in SCT recipients to date support the use of multi-dose regimens for most protein and polysaccharide-conjugate vaccine antigens. The consensus immunization schedule recommended by ACIP/IDSA/ASBMT provides guidance for centers to utilize available vaccines in their SCT populations. With the exception of pneumococcal disease, a schedule beginning at 12 months after SCT is reasonable given the low incidence of disease in HSCT recipients for most of the recommended vaccines and improved immune reconstitution in most recipients by one year post transplant. SCT recipients respond poorly to unconjugated pneumococcal polysaccharide vaccine and the development of polysaccharide-protein conjugate vaccines against S. pneumoniae holds promise to impact potentially on clinical disease in this population. In addition, the strategy of donor immunization may also be effective in eliciting early protective immune responses to vaccine antigens. Future challenges will be the development of safe and effective vaccines against the viral pathogens responsible for considerable morbidity and mortality after SCT.

Lymphocyte reconstitution following non-myeloablative hematopoietic stem cell transplantation follows two patterns depending on age and donor/recipient chimerism

The effect of mixed chimerism on the pace of post-transplant immune reconstitution is unknown. Using flow cytometry, recall and neo-antigen vaccine responses, and T cell receptor recombination excision circle (TREC) quantification, we evaluated phenotypic and functional characteristics of T and B cells in nine patients following non-myeloablative, HLA-identical peripheral blood stem cell transplantation for chronic granulomatous disease. Engraftment of T cell, B cell, and myeloid lineages proceeded at similar paces within each patient, but engraftment kinetics segregated patients into two groups: adults, who became full donor T cell chimeras before 6 months (rapid engrafters) and children, who became full donor T cell chimeras after 6 months or not at all (slow engrafters). Quantitative B cell recovery was achieved by 6 weeks after transplantation in children, but was delayed until 1 year in adults. Early quantitative B cell recovery was not accompanied by an early humoral immune response to tetanus toxoid (TT). Emergence of TT-specific T cell responses coincided with naive T cell reconstitution, as measured by CD4/CD45RA T cell recovery and TREC quantification. These data suggest that immune reconstitution occurs faster in pediatric patients who have prolonged mixed hematopoietic chimerism compared to adults, who have rapid donor stem cell engraftment.

Vaccines for transplant recipients

Immune dysregulation and immunosuppression regimens impact on the ability of transplant recipients to respond to immunizations. The distinct challenges of immunizations to benefit stem cell transplant recipients and solid organ transplant recipients are discussed separately. Recommended vaccines for stem cell transplant recipients and solid organ transplant candidates are suggested. New approaches to consider to enhance immune responses of transplant recipients are discussed.

Preventing opportunistic infections after hematopoietic stem cell transplantation: the Centers for Disease Control and Prevention, Infectious Diseases Society of America, and American Society for Blood and Marrow Transplantation Practice Guidelines and beyond

This review presents evidence-based guidelines for the prevention of infection after blood and marrow transplantation. Recommendations apply to all myeloablative transplants regardless of recipient (adult or child), type (allogeneic or autologous) or source (peripheral blood, marrow or cord blood) of transplant. In Section I, Dr. Dykewicz describes the methods used to rate the strength and quality of published evidence supporting these recommendations and details the two dozen scholarly societies and federal agencies involved in the genesis and review of the guidelines. In Section II, Dr. Longworth presents recommendations for hospital infection control. Hand hygiene, room ventilation, health care worker and visitor policies are detailed along with guidelines for control of specific nosocomial and community-acquired pathogens. In Section III, Dr. Boeckh details effective practices to prevent viral diseases. Leukocyte-depleted blood is recommended for cytomegalovirus (CMV) seronegative allografts, while ganciclovir given as prophylaxis or preemptive therapy based on pp65 antigenemia or DNA assays is advised for individuals at risk for CMV. Guidelines for preventing varicella-zoster virus (VZV), herpes simplex virus (HSV) and community respiratory virus infections are also presented. In Section IV, Drs. Baden and Rubin review means to prevent invasive fungal infections. Hospital design and policy can reduce exposure to air contaminated with fungal spores and fluconazole prophylaxis at 400 mg/day reduces invasive yeast infection. In Section V, Dr. Sepkowitz details effective clinical practices to reduce or prevent bacterial or protozoal disease after transplantation. In Section VI, Dr. Sullivan reviews vaccine-preventable infections and guidelines for active and passive immunizations for stem cell transplant recipients, family members and health care workers.

Immunization of pediatric solid organ transplant candidates and recipients

Organ transplantation has evolved from an experimental procedure to an accepted treatment for otherwise irreversible or congenital disorders. The immunosuppression necessary to prevent rejection enhances the severity of many infectious diseases and may potentially attenuate the response to vaccines designed to prevent disease. In spite of the frequency and severity of infectious diseases in organ transplant recipients, many children are not fully vaccinated before transplantation. The safety and efficacy of many of the currently available vaccines for solid organ transplant recipients have not been evaluated. We review the currently available data on immunization safety and efficacy, discuss experimental vaccines, and outline strategies to avoid vaccine-preventable diseases in pediatric organ transplant recipients.