Tetanus immunity in autologous bone marrow and blood stem cell transplant recipients

Improved serologic responses to DTaP over Tdap vaccination in adult hematopoietic cell transplant recipients

BACKGROUND

Hematopoietic cell transplantation (HCT) recipients have reduced antibody titers to tetanus, diphtheria, and pertussis. Tdap is approved for revaccinating adult HCT recipients in the United States, whereas DTaP is not approved in this population. To our knowledge, no studies to date have compared responses to DTaP versus Tdap in adult HCT patients. We conducted a retrospective study comparing responses to DTaP versus Tdap vaccines in otherwise similar adult HCT patients in order to determine if one of these vaccines elicits superior antibody responses.

METHODS

We evaluated 43 allogeneic and autologous transplant recipients as a combined cohort and as separate subsets for vaccine specific antibody titers and proportion of strong vaccine responders. Subset analysis focused on the autologous transplant recipients.

RESULTS

Higher median antibody titers were found to all vaccine components among DTaP recipients (diphtheria p = .021, pertussis p = .020, tetanus p = .007). DTaP recipients also had more strong responders to diphtheria and pertussis (diphtheria p = .002, pertussis p = .006). Among the autologous HCT recipient subset, there were more strong responders to diphtheria (p = .036).

CONCLUSIONS

Our data shows that post-HCT vaccination with DTaP leads to higher antibody titers and more strong responders, which suggests that DTaP is more effective than Tdap in HCT recipients.

Anti-infective vaccination strategies in patients with hematologic malignancies or solid tumors-Guideline of the Infectious Diseases Working Party (AGIHO) of the German Society for Hematology and Medical Oncology (DGHO)

Infectious complications are a significant cause of morbidity and mortality in patients with malignancies specifically when receiving anticancer treatments. Prevention of infection through vaccines is an important aspect of clinical care of cancer patients. Immunocompromising effects of the underlying disease as well as of antineoplastic therapies need to be considered when devising vaccination strategies. This guideline provides clinical recommendations on vaccine use in cancer patients including autologous stem cell transplant recipients, while allogeneic stem cell transplantation is subject of a separate guideline. The document was prepared by the Infectious Diseases Working Party (AGIHO) of the German Society for Hematology and Medical Oncology (DGHO) by reviewing currently available data and applying evidence-based medicine criteria.

Practical review of immunizations in adult patients with cancer

Compared with the general population, patients with cancer in general are more susceptible to vaccine-preventable infections, either by an increased risk due to the malignancy itself or immunosuppressive treatment. The goal of immunizations in these patients is therefore to provide protection against these infections, and to decrease the number of vulnerable patients who can disseminate these organisms. The proper timing of immunization with cancer treatment is key to achieving better vaccine protection. As the oncology field continues to advance, leading to better quality of life and longer survival, immunization and other aspects of preventive medicine ought to move to the frontline in the care of these patients. Herein, we review the vaccines most clinically relevant to patients with cancer, as well as special cases including vaccines after splenectomy, travel immunization and recommendations for family members.

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.

Vaccination of immunocompromised patients

Vaccination of immunocompromised patients is challenging both regarding efficacy and safety. True efficacy data are lacking so existing recommendations are based on immune responses and safety data. Inactivated vaccines can generally be used without risk but the patients who are most at risk for infectious morbidity and mortality as a result of their severely immunosuppressed state are also those least likely to respond to vaccination. However, vaccination against pneumococci, Haemophilus influenzae and influenza are generally recommended. Live vaccines must be used with care because the risk for vaccine-associated disease exists.

Defects in lymphocyte subsets and serological memory persist a median of 10 years after high-dose therapy and autologous progenitor cell rescue for malignant lymphoma

The number of survivors having undergone high-dose therapy (HDT) followed by auto-SCT continues to increase, although some of the long-term sequelae remain incompletely understood. The immunological status and quality of life of 37 HDT/auto-SCT survivors with lymphoma in continuous remission of ≥3 years were assessed alongside 14 age-matched controls. At a median follow-up of 10.5 years (range 2.2-20.2) following HDT/auto-SCT, the proportion of CD4(+) cells remained significantly reduced in patients compared with controls (median 43.4% vs 62.5%, respectively; P = < 0.001), predominantly a result of sustained reduction in the naive CD4(+) component (P < 0.001). Naive CD8(+) lymphocytes (P = 0.014) and transitional B cells (P = 0.008) were also significantly reduced, but differences in other lymphocyte subsets were not observed. Uptake of revaccination following HDT/auto-SCT was sporadic; between 11% and 33% of patients had serological titres outside the protective ranges for five of six routinely used vaccines. In the main, patients were found to have a good quality of life, although their EORTC QLQ-C30 questionnaire scores were significantly lower for the physical and social functioning domains compared with controls. Ten years after HDT/auto-SCT immunological deficits persist; to avoid excess risk of preventable disease, serological immunity should be assessed post HDT/auto-SCT followed by appropriate revaccination.

Immunization of hematopoietic stem cell transplant recipients against vaccine-preventable diseases

Worldwide, over 40,000 hematopoietic cell transplants (HCT) are carried out each year, with the majority of patients surviving long term. Owing to their new immune systems, these patients are susceptible to a variety of preventable infectious diseases. The 2009 influenza pandemic, the increase in pertussis and antibiotic-resistant pneumococcus, as well as recent outbreaks of measles and mumps in immunocompetent individuals further highlight the need for effective revaccination of HCT recipients. Post-transplant vaccine guidelines, including those published in 2009, recommend immunization of all patient groups at fixed times post-HCT. Although early vaccination to protect against vaccine-preventable diseases is desirable, there are still limited data on whether this approach is efficacious in patient groups whose immune recovery differs from recipients of an unmodified HLA-matched sibling transplant. In the absence of such data, prospective trials are needed to better define the optimal timing for immunizing recipients of alternative donors. Ideally, such trials should be designed to identify biological markers that will predict an optimal and durable vaccine response.

Pertussis immunity and response to tetanus-reduced diphtheria-reduced pertussis vaccine (Tdap) after autologous peripheral blood stem cell transplantation

Pertussis is a highly contagious respiratory infection characterized by prolonged cough and inspiratory whoop. Despite widespread vaccination of children aged<7 years, its incidence is steadily increasing in adolescents and adults, because of the known decrease in immunity following childhood immunization. In an effort to reduce pertussis in adolescents and adults, 2 vaccines containing tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) (BOOSTRIX and Adacel) were licensed in 2005 for use in adolescents, 1 of which (Adacel) contains less pertussis toxoid (PT) for use in adults. This study assessed pertussis titers in 57 adult survivors of an autologous peripheral blood stem cell transplantation (PBSCT; median age, 37.5 years), 28 of whom were subsequently vaccinated with Tdap containing 2.5microg of PT (Adacel). The median time to Tdap administration was 3 years posttransplantation. Before vaccination, 87% of the patients lacked pertussis immunity. Only 2 of the 28 patients developed a >2-fold response to PT following vaccination with Tdap. These data suggest that autologous transplantation recipients are highly susceptible to pertussis and that immunization with 2.5microg of PT induces an inadequate response. Prospective trials evaluating BOOSTRIX, containing 8microg/dose of PT (approved for adults in December 2008) are warranted in this vulnerable population undergoing transplantation.

Resetting the adaptive immune system after autologous stem cell transplantation: lessons from responses to vaccines

Autologous stem cell transplantation (ASCT) to treat autoimmune diseases (AID) is thought to reset immunological memory directed against autoantigens. This hypothesis can only be studied indirectly because the exact nature of the pathogenetic autoantigens is unknown in most AID. Therefore, 19 children with juvenile idiopathic arthritis (JIA) or systemic lupus erythematodes (SLE) and 10 adults with multiple sclerosis (MS) were vaccinated with the T-cell-dependent neoantigen rabies and the recall antigen tetanus toxoid after, respectively before, bone marrow harvest. Both vaccinations were repeated after ASCT. All except two of the responders mounted a primary antibody response to rabies after revaccination, and 44% of the responders mounted a primary antibody response to tetanus boost after ASCT. These data show that immunological memory to a neoantigen is lost in most patients with AID after immunoablative pretreatment; however, memory to a recall antigen boosted before bone marrow harvest is only lost in part of the patients. Disease progression was arrested in all patients with JIA/SLE except one, but only in a minority of MS patients. Clinical outcome on a per case basis was not associated with the profile of the immune response toward the vaccination antigens after ASCT.

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.

Loss of hepatitis A virus antibodies after bone marrow transplantation

Reimmunization guidelines have recommended the inactivated HAV vaccine for hematopoietic stem cell transplant (HSCT) recipients living in or traveling to areas where hepatitis A is endemic. As a shift from high to medium hepatitis A endemicity has been observed in several countries in Latin America, we conducted a retrospective study to evaluate the prevalence of hepatitis A pre-bone marrow transplant (BMT) and the loss of specific antibodies in consecutive stored serum samples from 77 BMT recipients followed up from 82 to 1530 days. The prevalence of HAV antibodies was 92.2% before BMT. As vaccine was not available in Brazil when the samples were taken, it was assumed that this prevalence reflects natural infection. Survival analysis showed that the probability of becoming seronegative was 4.5% (+/-2.6%), 7.9% (+/-3.4%), 10.1% (+/-4.0%), 23.4% (+/-9.6%) at 1, 2, 3 and 4 years after transplant, respectively. The loss of HAV antibodies was significantly associated with longer follow-up (P=0.0015), younger age (P=0.049) and acute graft-versus-host disease (P=0.035). As most reimmunization protocols start around day +365, in developing countries with similar HAV endemicity, BMT recipients should have serological screening before HAV vaccination and the inactivated vaccine should be advised to those seronegative.

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.

Vaccination of stem cell transplant recipients: recommendations of the Infectious Diseases Working Party of the EBMT

Over the last 25 years, the numbers of hematopoietic stem cell transplant (SCT) patients have increased rapidly. Infections have been major obstacles for successful transplantation. Thus, infection prevention is very important in transplant recipients. As the results of transplantation have improved, the number of long-term survivors has increased. Vaccination is a potentially important strategy for reducing the risk for vaccine-preventable infections after SCT. The EBMT produced recommendations for vaccination of SCT recipients published in Bone Marrow Transplantation in 1995. This paper updates the previous recommendations based on current knowledge.

Antibody titers and immune response to diphtheria-tetanus-pertussis and measles-mumps-rubella vaccination in children treated for acute lymphoblastic leukemia

The objective of this study was to investigate the diphtheria-tetanus-pertussis and/or measles-mumps antibody titers before and after vaccination at various time points of acute lymphoblastic leukemia (ALL) therapy and to suggest an appropriate vaccination approach for ALL patients. The authors studied 37 ALL patients and 14 healthy control subjects, divided into three groups. In group 1 (newly diagnosed patients), baseline anti-diphtheria, anti-tetanus, and anti-pertussis titers were determined. Patients in group 2 (on maintenance chemotherapy) and group 3 (patients not receiving therapy for 3-6 months) were vaccinated with diphtheria-tetanus with or without acellular pertussis; group 3 and control subjects were also given measles-mumps-rubella vaccine. Preimmunization and 1-month postimmunization titers were drawn. Preimmunization anti-diphtheria and anti-tetanus antibody titers between the groups and the controls were statistically similar. The seropositivity rate for anti-measles antibody in group 3 was significantly lower than controls. After vaccination, all of the patients developed protective anti-diphtheria and anti-tetanus antibody titers. The seroconversion rates of group 3 and controls for anti-measles and anti-mumps antibodies were statistically similar. The results showed that patients on maintenance therapy and after cessation of therapy made good antibody responses to diphtheria and tetanus toxoids, but response to measles and mumps vaccines was not as sufficient as toxoid vaccines. Children with ALL can receive the appropriate vaccines during and after maintenance treatment.

Recovery from and consequences of severe iatrogenic lymphopenia (induced to treat autoimmune diseases)

To ascertain the consequences of severe leukopenia and the tempo of recovery, we studied the immunity of 56 adult patients treated for multiple sclerosis or systemic sclerosis with autologous CD34 cell transplantation using extremely lymphoablative conditioning. NK cell, monocyte, and neutrophil counts recovered to normal by 1 month; dendritic cell and B cell counts by 6 months; and T cell counts by 2 years posttransplant, although CD4 T cell counts remained borderline low. Initial peripheral expansion was robust for CD8 T cells but only moderate for CD4 T cells. Subsequent thymopoiesis was slow, especially in older patients. Importantly, levels of antibodies, including autoantibodies, did not drop substantially. Infections were frequent during the first 6 months, when all immune cells were deficient, and surprisingly rare (0.21 per patient year) at 7-24 months posttransplant, when only T cells (particularly CD4 T cells) were deficient. In conclusion, peripheral expansion of CD8 but not CD4 T cells is highly efficient. Prolonged CD4 lymphopenia is associated with relatively few infections, possibly due to antibodies produced by persisting pretransplant plasma cells.

Immunization of immunocompromised persons

Advances in medicine, science, and technology have led to increasing numbers of people in the general population with altered host defenses. The risk for clinical infection in an immunocompromised host, such as a person who has received a solid organ transplant, is determined largely by the interaction between two factors: the epidemiologic exposures the person encounters and the person's net state of immunosuppresson. Vaccination represents a crucial approach for preventing infection in the general public and immunocompromised persons. This article reviews the benefits of and risks for immunization in immunocompromised persons and provides recommendations for the use of specific vaccines.

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.

Loss of hepatitis A virus (HAV) antibodies after peripheral stem cell transplantation (PSCT)

The majority of patients with hepatitis A have a benign course, but some may develop fulminant hepatitis and hematological complications. Peripheral stem cell transplantation (PSCT) is associated with loss of immunity. There are no data regarding loss of HAV antibodies (anti-HAV) after PSCT. We retrospectively evaluated the persistence of anti-HAV in a nonvaccinated population that underwent PSCT. Serum detection of anti-HAV was determined before and after PSCT using a qualitative commercially available enzyme immunoassay. From January 1997 to March 2001, 136 (68%) of 201 patients tested (+) for anti-HAV prior to PSCT. Subsequent investigation of anti-HAV was possible in 36 of these patients at a median of 12 months after PSCT. The median age of patients was 47 years old; they had diagnoses of hematological malignancies (33) and solid tumors (three), and underwent autologous (31) and allogenic (five) PSCT. A total of 31 (86%) of 36 patients remained anti-HAV (+) and five (14%) became (-) after PSCT. The variables age, sex, diagnosis, type of PSCT, time of testing, and number of CD34 cells infused were not predictors of loss of anti-HAV. In conclusion, 14% of 36 nonvaccinated anti-HAV (+) patients lost their antibodies at a median of 12 months after PSCT.

[Post-transplantation vaccination of bone-marrow transplant recipients]

BACKGROUND

Patients subject to bone marrow transplantation (BMT) and other blood stem cell transplantations are severely immunocompromised after transplantation. Some studies have suggested that post-transplantation loss of acquired immunity may play a role. The objective of this study was to determine the susceptibility to vaccine-preventable diseases in people subject to BMT and the serologic response after vaccination.

PATIENTS AND METHOD

Study population was people subject to transplantation at least 6 months before initiating vaccination and without immunosuppressive treatment at that time. A prevaccination serologic analysis was carried out, and the hepatitis B, the adult tetanus-diphtheria (Td), the IPV, the influenza and the pneumococccal vaccines were administered in accordance with standard guidelines Depending on the immune status of the patient according to the serologic analysis, the MMR vaccine was administered no sooner than 18 months after transplantation. After vaccination, a serologic analysis was carried out to determine the response.

RESULTS

The mean time SD between transplant and the initiation of vaccination was 3.2 2.9 years. Of the 122 recipients of BMT (average age 35.8 13 years; 54.2% male), 51.7% received an allogenic and 48.3% an autologous transplant. Before vaccination, the susceptibility was 48.2% for tetanus, 66.7% for diphtheria, 74.1% for pertussis, 85.9% for hepatitis B, 13.4% for measles, 36.7% for rubella and 9.2% for mumps. The rates of seroconversion with protective titers after vaccination for tetanus, diphtheria and hepatitis B were 94%, 67% and 75% respectively. The response to the MMR vaccine was greater than 70%, with a second dose of the vaccine being needed in 26% of patients.

CONCLUSIONS

Susceptibility to vaccine-preventable diseases in transplanted patients is high. The acceptable response to vaccination justifies the development of specific programs. Given the special characteristics of this group of patients, vaccination programs must be simple and flexible.

Immunization recommendations for adults with cancer

OBJECTIVE

To review the published literature on immunizing nonbone marrow transplant adult cancer patients, summarize the findings, and make recommendations for the use of vaccines in this population.

DATA SOURCE

A search of MEDLINE and CancerLit was conducted (1966-June 2001) to find English-language clinical studies and review articles pertaining to immunization, vaccines, and cancer in humans. Recommendations of the Advisory Committee on Immunization Practices were used extensively. References of each identified article were subsequently reviewed for additional relevant articles.

STUDY SELECTION AND DATA EXTRACTION

Representative epidemiologic reports, clinical trials, and recommendations of expert panels are summarized in this report. Relevant information was selected to describe the epidemiology of vaccine-preventable diseases, efficacy of the vaccines, and recommendations specific to adults with cancer.

DATA SYNTHESIS

In general, adults with cancer are at least at the same risk of infection with vaccine-preventable diseases as are healthy populations. Because of their compromised immune function, many patients who have undergone cancer treatment are specifically at increased risk of morbidity and mortality associated with measles and varicella infections. Asplenic patients with lymphoma are at increased risk of fulminant bacterial infections. Influenza infection is associated with significant morbidity in cancer patients. Although the protection conferred by immunization is lower in immunosuppressed patients with cancer, immunization with inactivated vaccines is indicated. Live vaccines should not be used except in very rare instances.

CONCLUSIONS

Immunization of adults with cancer is a critical component of their care. Although additional research is necessary, following established recommendations may protect individuals with malignancies from significant morbidity and mortality associated with vaccine-preventable diseases.

Humoral immunity to viral and bacterial antigens in lymphoma patients 4-10 years after high-dose therapy with ABMT. Serological responses to revaccinations according to EBMT guidelines

The aim of this study was to investigate the late effects of ABMT on the immune system with regard to protective humoral immunity against common antigens and responses to recall antigens (vaccines). The vaccines were given according to EBMT guidelines from 1995. The protocol included 35 patients with malignant lymphoma in CR 4-10 years after ABMT, and 35 controls. The results show that prior to ABMT the proportion of patients with protective immunity against poliomyelitis, tetanus and diphtheria was similar to that of controls. At study entry 4-10 years after ABMT, the proportion of patients with protective immunity against poliomyelitis and diphtheria was reduced, while all patients maintained protection against tetanus. A significant decrease in geometric mean antibody concentrations or titres was observed against all three antigens during this period. Serum levels of antibodies against different pneumococcal serotypes were lower in the patients than in the controls prior to vaccination. The responses to pneumococcal vaccination, which is considered to be a T cell-independent vaccine, were studied. Unlike controls, a minority of patients achieved protective levels of antibodies after a single vaccination. Despite persistent levels of protective antibodies in many patients post ABMT, secondary booster responses after one vaccination with T cell-dependent vaccines (tetanus, diphtheria and polio) were absent. In conclusion, this study shows that post ABMT, a full re-vaccination program was necessary to mount responses comparable to those observed after a single vaccination in controls.

[Immunization for children treated for solid tumors: what are the guidelines?]

There is no agreement on immunization of children treated with chemotherapy (CT) for solid tumors. Based on a review of the literature, we have attempted to establish guidelines on this subject. Except for hepatitis B vaccine, there is no argument to support the use of vaccine during CT. After a standard CT, a 3-month washout period appears to be necessary before starting an immunization program for a child not previously vaccinated, or to proceed with the recommended booster injections for diphteria anatoxin, tetanus vaccine, poliomyelitis inactivated vaccine, pertussis vaccine, and haemophilus influenza type b vaccine if the child is less than 5 years old. For mumps, measles, and rubella live vaccines, a longer post-CT washout of 6 months is suggested for the initial immunization, or for a revaccination of a child proved to be negative for all three serologies. Following high-dose CT a minimal 12-months term and a normalization of the blood lymphocytes count is necessary before planning booster injections once having checked for antidiphteria, tetanic, polio, measles, mumps, rubella and +/- haemophilus antibody titles. We don't find any reason to recommend a systematic varicella immunization in pediatric oncology. Pneumococcal vaccine is recommended in case of asplenia. Any other vaccination (BCG, influenza, yellow fever) must be evaluated individually.

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.

Recovery of immune reactivity after T-cell–depleted bone marrow transplantation depends on thymic activity

To evaluate the importance of the thymus for the reconstitution of immunity in recipients of a T-cell–depleted bone marrow, we measured the appearance of CD4+CD45RA+RO−naive T cells (thymic rebound), restoration of the diversity of the T-cell–receptor (TCR) repertoire and the response to vaccinations with tetanus toxoid (TT). Repopulation by CD4+CD45RA+RO− thymic emigrants varied among patients, starting at approximately 6 months after transplantation. Young patients reconstituted swiftly, whereas in older patients, the recovery of normal numbers of naive CD4+ T cells could take several years. Restoration of TCR diversity was correlated with the number of naive CD4+CD45RA+RO− T cells. Moreover, the extent of the thymic rebound correlated with the patient's capacity to respond to vaccinations. Patients without a significant thymic rebound at the moment of vaccination (CD4+CD45RA+RO− T cells less than 30 μL) did not respond, or responded only marginally even after 3 boosts with TT. We conclude that during the first year after transplantation, the absence of an immune response is due mainly to the loss of an adequate T-cell repertoire. Restoration of the repertoire can come only from a thymic rebound that can be monitored by measuring the increase of CD4+CD45RA+RO−naive T cells. This will allow postponing revaccinations to a moment when the patient will be able to respond more effectively. This may be particularly useful in the elderly patient who, owing to low thymic activity, might not yet be able to respond 1 year after transplant when revaccinations are usually scheduled.

Recovery of immune reactivity after T-cell–depleted bone marrow transplantation depends on thymic activity

To evaluate the importance of the thymus for the reconstitution of immunity in recipients of a T-cell–depleted bone marrow, we measured the appearance of CD4+CD45RA+RO−naive T cells (thymic rebound), restoration of the diversity of the T-cell–receptor (TCR) repertoire and the response to vaccinations with tetanus toxoid (TT). Repopulation by CD4+CD45RA+RO− thymic emigrants varied among patients, starting at approximately 6 months after transplantation. Young patients reconstituted swiftly, whereas in older patients, the recovery of normal numbers of naive CD4+ T cells could take several years. Restoration of TCR diversity was correlated with the number of naive CD4+CD45RA+RO− T cells. Moreover, the extent of the thymic rebound correlated with the patient's capacity to respond to vaccinations. Patients without a significant thymic rebound at the moment of vaccination (CD4+CD45RA+RO− T cells less than 30 μL) did not respond, or responded only marginally even after 3 boosts with TT. We conclude that during the first year after transplantation, the absence of an immune response is due mainly to the loss of an adequate T-cell repertoire. Restoration of the repertoire can come only from a thymic rebound that can be monitored by measuring the increase of CD4+CD45RA+RO−naive T cells. This will allow postponing revaccinations to a moment when the patient will be able to respond more effectively. This may be particularly useful in the elderly patient who, owing to low thymic activity, might not yet be able to respond 1 year after transplant when revaccinations are usually scheduled.