Donor immunization with pneumococcal conjugate vaccine and early protective antibody responses following allogeneic hematopoietic cell transplantation

A Phase 3, Randomized, Double-Blind, Comparator-Controlled Study to Evaluate Safety, Tolerability, and Immunogenicity of V114, a 15-Valent Pneumococcal Conjugate Vaccine, in Allogeneic Hematopoietic Cell Transplant Recipients (PNEU-STEM)

BACKGROUND

Individuals who receive allogeneic hematopoietic cell transplant (allo-HCT) are immunocompromised and at high risk of pneumococcal infections, especially in the months following transplant. This study evaluated the safety and immunogenicity of V114 (VAXNEUVANCE; Merck, Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA), a 15-valent pneumococcal conjugate vaccine (PCV), when given to allo-HCT recipients.

METHODS

Participants received 3 doses of V114 or PCV13 (Prevnar 13; Wyeth LLC) in 1-month intervals starting 3-6 months after allo-HCT. Twelve months after HCT, participants received either PNEUMOVAX 23 or a fourth dose of PCV (if they experienced chronic graft vs host disease). Safety was evaluated as the proportion of participants with adverse events (AEs). Immunogenicity was evaluated by measuring serotype-specific immunoglobulin G (IgG) geometric mean concentrations (GMCs) and opsonophagocytic activity (OPA) geometric mean titers (GMTs) for all V114 serotypes in each vaccination group.

RESULTS

A total of 274 participants were enrolled and vaccinated in the study. The proportions of participants with AEs and serious AEs were generally comparable between intervention groups, and the majority of AEs in both groups were of short duration and mild-to-moderate intensity. For both IgG GMCs and OPA GMTs, V114 was generally comparable to PCV13 for the 13 shared serotypes, and higher for serotypes 22F and 33F at day 90.

CONCLUSIONS

V114 was well tolerated in allo-HCT recipients, with a generally comparable safety profile to PCV13. V114 induced comparable immune responses to PCV13 for the 13 shared serotypes, and was higher for V114 serotypes 22F and 33F. Study results support the use of V114 in allo-HCT recipients. Clinical Trials Registration. clinicaltrials.gov (NCT03565900) and European Union at EudraCT 2018-000066-11.

Impact of Donor and Recipient SARS-CoV-2 Vaccination or Infection on Immunity after Hematopoietic Cell Transplantation

The role of donor and recipient Coronavirus disease 2019 (COVID-19) immunologic status pre-transplantation has not been fully investigated in allogeneic hematopoietic stem cell transplantation (HSCT) recipients. Given the poor immunogenicity to vaccines in this population and the serious outcomes of COVID-19, adoptive transfer of immunity may offer important insight into improving protection for this vulnerable population. In this study, we evaluated the role of adoptive transfer of immunity at 1 month post-transplantation and 6 months post-transplantation after vaccination of recipients, based on pre-transplantation severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and infection exposures of both recipient and donor. Using banked specimens from related donor allogeneic HSCT recipients and clinical data from both donors and recipients, anti-Spike (S) IgG titers were analyzed at 1, 3, and 6 months post-transplantation according to prior SARS-CoV-2 immunologic exposures. Recipients were excluded if they had received SARS-CoV-2 monoclonal antibodies or had infection in the first 6 months post-transplantation. Of the 53 recipient-donor pairs, 29 donors and 24 recipients had prior SARS-CoV-2 immunologic exposure. Recipient-donor pairs with no prior SARS-CoV-2 exposure (D0R0) had significantly lower anti-S IgG titers at 1 month compared to those with prior exposures (D1R1) (D0R0: median, 2.43 [interquartile range (IQR), .41 to 3.77]; D1R1: median, 8.42; IQR, 5.58 to 12.20]; P = .008). At 6 months, anti-S IgG titers were higher in recipients who were vaccinated at 3 months post-transplantation in the D1R1 cohort (median IgG, 148.34; IQR, 92.36 to 204.33) compared with the D0R0 cohort (median IgG, 38.74; IQR, 8.93 to 119.71). Current strategies should be optimized to enhance SARS-CoV-2 protection for HSCT recipients, including augmentation of the immune response for both donors and recipients prior to transplantation.

Three doses of a recombinant conjugated SARS-CoV-2 vaccine early after allogeneic hematopoietic stem cell transplantation: predicting indicators of a high serologic response-a prospective, single-arm study

Background

Allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients must be vaccinated against SARS-CoV-2 as quickly as possible after transplantation. The difficulty in obtaining recommended SARS-CoV-2 vaccines for allo-HSCT recipients motivated us to utilize an accessible and affordable SARS-CoV-2 vaccine with a recombinant receptor-binding domain (RBD)-tetanus toxoid (TT)-conjugated platform shortly after allo-HSCT in the developing country of Iran.

Methods

This prospective, single-arm study aimed to investigate immunogenicity and its predictors following a three-dose SARS-CoV-2 RBD-TT-conjugated vaccine regimen administered at 4-week (± 1-week) intervals in patients within 3-12 months post allo-HSCT. An immune status ratio (ISR) was measured at baseline and 4 weeks (± 1 week) after each vaccine dose using a semiquantitative immunoassay. Using the median ISR as a cut-off point for immune response intensity, we performed a logistic regression analysis to determine the predictive impact of several baseline factors on the intensity of the serologic response following the third vaccination dose.

Results

Thirty-six allo-HSCT recipients, with a mean age of 42.42 years and a median time of 133 days between hematopoietic stem cell transplant (allo-HSCT) and the start of vaccination, were analyzed. Our findings, using the generalized estimating equation (GEE) model, indicated that, compared with the baseline ISR of 1.55 [95% confidence interval (CI) 0.94 to 2.17], the ISR increased significantly during the three-dose SARS-CoV-2 vaccination regimen. The ISR reached 2.32 (95% CI 1.84 to 2.79; p = 0.010) after the second dose and 3.87 (95% CI 3.25 to 4.48; p = 0.001) after the third dose of vaccine, reflecting 69.44% and 91.66% seropositivity, respectively. In a multivariate logistic regression analysis, the female sex of the donor [odds ratio (OR) 8.67; p = 0.028] and a higher level donor ISR at allo-HSCT (OR 3.56; p = 0.050) were the two positive predictors of strong immune response following the third vaccine dose. No serious adverse events (i.e., grades 3 and 4) were observed following the vaccination regimen.

Conclusions

We concluded that early vaccination of allo-HSCT recipients with a three-dose RBD-TT-conjugated SARS-CoV-2 vaccine is safe and could improve the early post-allo-HSCT immune response. We further believe that the pre-allo-HSCT SARS-CoV-2 immunization of donors may enhance post-allo-HSCT seroconversion in allo-HSCT recipients who receive the entire course of the SARS-CoV-2 vaccine during the first year after allo-HSCT.

Allogeneic hematopoietic stem cell transplantation in the COVID-19 era

Allogeneic hematopoietic stem-cell transplantation (allo-HSCT) recipients are especially vulnerable to coronavirus disease 19 (COVID-19), because of their profound immunodeficiency. Indeed, the first pandemic wave was marked by a high mortality rate in this population. Factors increasing immunodepression such as older age, immunosuppressive treatments or a short delay between transplant and infection appear to worsen the prognosis. Many changes in clinical practice had to be implemented in order to limit this risk, including postponing of transplant for non-malignant diseases, preference for local rather than international donations and for peripheral blood as stem cell source, and the widespread use of cryopreservation. The great revolution in the COVID-19 pandemic came from the development of mRNA vaccines that have shown to be able to prevent severe forms of the disease. More than 75% of allo-HSCT recipients develop seroconversion after 2 doses of vaccine. Multiple studies have identified lymphopenia, exposure to immunosuppressive or anti-CD20 therapies, and a short post-transplant period as factors associated with a poor response to vaccination. The use of repeated injections of the vaccine, including a third dose, not only improves the seroconversion rate but also intensifies the immune response, both in B cells and T cells. Vaccines are an effective and well-tolerated method in this high-risk population. Some studies investigated the possibility of immune protection being transferred from a vaccinated donor to a recipient, with encouraging initial results. However, dynamic mutations and immune escape of the virus can lead to breakthrough infections with new variants in vaccinated individuals and still represent a threat of severe disease in allo-HSCT recipients. New challenges include the need to adapt vaccine protection to emerging variants.

Tick-Borne Encephalitis Specific Lymphocyte Response after Allogeneic Hematopoietic Stem Cell Transplantation Predicts Humoral Immunity after Vaccination

The aim of this prospective study was to assess lymphocyte proliferative and cytokine response prior to and following tick-borne encephalitis (TBE) immunization among patients after allogeneic hematopoietic stem cell transplantation (HSCT). Seventeen adult patients 11–13 months after HSCT and eight unvaccinated healthy adults received up to three TBE vaccinations. Following in vitro stimulation with TBE-antigen, lymphocyte proliferation and cytokine secretion (IL-2, IL-10, IL-13, TNF-alpha, IFN-gamma, GM-CSF) were analyzed by thymidine incorporation assay and the Luminex system. Ten patients (59%) showed significant baseline TBE-specific lymphocyte proliferation (stimulation index (SI) > 3) prior to vaccination, but none of the unvaccinated controls (p = 0.002). All patients with a TBE-specific antibody response after two vaccinations (at least 2-fold increase of neutralization test titers) exhibited a strong TBE-specific lymphocyte proliferative response at baseline (SI > 10). Patients with sibling donors had a significantly stronger baseline TBE-specific lymphocyte proliferative and IL-13 cytokine response than patients with unrelated donors (p < 0.05). In conclusion, a relevant proportion of patients showed TBE-specific lymphocyte proliferative and cytokine responses prior to vaccination after HSCT, which predicted the humoral response to the vaccine. Patients with vaccinated sibling donors were more likely to elicit a cellular immune response than patients with unrelated donors of unknown vaccination status.

Coronavirus disease 2019 vaccination in transplant recipients

PURPOSE OF REVIEW

Coronavirus disease 2019 (COVID-19) vaccination is considered one of the most promising and socioeconomically sustainable strategy to help control the pandemic and several vaccines are currently being distributed in nationwide mass immunization campaigns. Very limited data are available on benefits and risks of COVID-19 vaccination in immunocompromised patients and in particular in solid organ or hematopoietic stem cell transplant recipients as they were excluded from phase III trials. This review summarizes current knowledge, international guidelines and controversies regarding COVID-19 vaccination in these vulnerable populations.

RECENT FINDINGS

Various COVID-19 vaccine platforms showed good efficacy in phase III trials in the immunocompetent and there are data arising on the safety and immunogenicity of these vaccines in the immunocompromised population.

SUMMARY

Transplant recipients could benefit significantly from COVID-19 vaccination, both through active immunization provided they elicit protective vaccine responses, and probably through cocooning by immunization of caregivers and healthcare personnel and thus reducing the risk of SARS-coronavirus-2 exposure. Although awaiting more data on the safety and efficacy of COVID-19 vaccines to inform potential adaptations of vaccine regimens, we strongly recommend prioritizing COVID-19 vaccination of solid and hematopoietic stem cell transplant recipients to decrease COVID-19-related morbidity and mortality.

Vaccination of the Stem Cell Transplant Recipient and the Hematologic Malignancy Patient

Patients with hematologic malignancy or those who undergo hematopoietic stem cell transplantation experience variable degrees of immunosuppression, dependent on underlying disease, therapy received, time since transplant, and complications, such as graft-versus-host disease. Vaccination is an important strategy to mitigate onset and severity of certain vaccine-preventable illnesses, such as influenza, pneumococcal disease, or varicella zoster infection, among others. This article highlights vaccines that should and should not be used in this patient population and includes general guidelines for timing of vaccination administration and special considerations in the context of newer therapies, recent vaccine developments, travel, and considerations for household contacts.

Antipneumococcal Seroprotection Years After Vaccination in Allogeneic Hematopoietic Cell Transplant Recipients

Background

International guidelines recommend vaccinating allogeneic hematopoietic cell transplant (HCT) recipients at 3 months after transplant, giving 3 doses of pneumococcal conjugate vaccine (PCV) followed by either a dose of 23-valent pneumococcal polysaccharide vaccine (PSV23) or a fourth PCV dose in the case of graft-versus-host disease (GvHD). However, the long-term immunity after this regimen is unknown, and there is no recommendation from 24 months after transplant regarding boosts. Our objective was to assess the antipneumococcal antibody titers and seroprotection rates of allogeneic HCT recipients years after different schedules of vaccination.

Methods

We assessed 100 adult HCT recipients a median of 9.3 years (range: 1.7–40) after transplant. All patients had received at least one dose of PCV and were assessed for antipneumococcal immunoglobulin G (IgG) antibody titers against the 7 serotypes shared by PCV7, PCV13, and PSV23. Sixty-six percent of the patients had been vaccinated according to the current guidelines.

Results

Considering an IgG titer ≥ 0.35 µg/mL as protective for each serotype, the seroprotection rate was 50% for 7/7 serotypes and 70% for 5/7 serotypes, with no differences between the different vaccination schedules. The lack of seroprotection was associated with a transplant performed not in complete remission or from a cord-blood unit, a relapse after transplant, or chronic GvHD at assessment.

Conclusion

Because only half of the vaccinated patients had long-term protection, pending prospective studies defining the best boost program after the initial one, we recommend the assessment of specific IgG titers starting from 24 months to decide for further doses.

Clinical Effectiveness of Conjugate Pneumococcal Vaccination in Hematopoietic Stem Cell Transplantation Recipients

Hematopoietic stem cell transplantation (HSCT) recipients are vulnerable to invasive pneumococcal disease (IPD), with reported IPD rates ranging from 3.81 to 22.5/1000 HSCT. This IPD risk could relate to immunodeficiency, low vaccination uptake, and poor immunogenicity of pneumococcal polysaccharide vaccine (PPV). Literature comparing the clinical effectiveness of pneumococcal conjugate vaccination (PCV) and PPV after HSCT is limited. In this retrospective analysis of HSCT recipients at our center from 2004 to 2015, we evaluated vaccination uptake and compared IPD rates in patients receiving PPV (pre-2010 group) and PCV (post-2010 group). IPD was determined from microbiological results for all HSCT recipients from January 2004 to June 30, 2019. Eight hundred patients had a total of 842 HSCT events, including autologous HSCT (auto-HSCT; n = 562) and allogeneic HSCT (allo-HSCT; n = 280). More than 90% of the HSCT recipients were enrolled, and >93% of surviving HSCT recipients completed the vaccination protocol. Fifteen IPD episodes occurred in 13 patients between 2004 and June 30, 2019. Thirteen episodes occurred in the pre-2010 group, even though 9 of 13 (69%) serotyped isolates were covered by PPV. Two episodes occurred in the post-2010 group; neither serotype was covered by PCV. Thus, with PCV introduction, IPD rate was significantly reduced from 38.5/1000 unique HSCTs pre-2010 to 4.0/1000 unique HSCTs post-2010 (P < .001). A significant reduction was seen in both auto-HSCTs (from 29.4 to 3.1 /1000 unique auto-HSCTs; P = .011) and allo-HSCTs (from 58.3 to 5.6/1000 unique allo-HSCTs; P = .011). PCV demonstrated superior clinical effectiveness over PPV, highlighting its importance in preventing infectious complications after HSCT. Robust vaccination programs at transplantation centers are needed to optimize vaccination uptake and completion.

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.

Long-term pneumococcal vaccine immunogenicity following allogeneic hematopoietic stem cell transplantation

Infection with Streptococcus pneumoniae is a life-threatening, but vaccine preventable complication in patients with allogeneic hematopoietic stem cell transplantation (allo-HSCT). The international consensus on post allo-HSCT immunization schedules, starting 3-6 months after HSCT, focuses on short-term immunogenicity while long-term immunogenicity is not well characterized. The current Dutch immunization schedule, which starts at 12 months post allo-HSCT, was developed as a result of concerns on the coverage of long-term immunogenicity in international guidelines. We recently encountered two cases of allo-HSCT recipients who developed invasive pneumococcal disease (IPD) despite adequate revaccinations, which led us to question the immunogenicity of pneumococcal vaccinations in this patient group, and whether the currently existing vaccination schedules are appropriate. We included allo-HSCT recipients, vaccinated from one year after transplantation, and tested antibody responses to pneumococcal vaccination. We also performed a systematic review. Antibody concentrations were measured in 42 of 103 (41%) patients, with a response rate of 85% to PCV13 and 62% to PPSV23-unique serotypes. In six relevant studies, protection rates varied between 64 and 98%. Antibody responses in early and late vaccination schedules were similar, but adequate antibody responses were maintained better after late vaccination. Therefore, we propose a vaccination schedule that combines the advantages of early and late vaccination. This new schedule has been introduced since March 2018 in the two academic hospitals in Amsterdam, The Netherlands.

Vaccinating donors for hematopoietic cell transplantation: A systematic review and future perspectives

Allogeneic hematopoietic cell transplantation (Allo-HCT) recipients are at an increased risk of infectious complications, which is a major cause of morbidity and mortality post-transplant. Vaccination of donors is one of the strategies that has been studied to improve immune reconstitution post-transplant, however the efficacy and safety of this strategy is not well reviewed in the literature. In this systematic review we sought to evaluate the current strategies of donor vaccination along with their immunogenicity, effectiveness and safety. Utilizing strict selection criteria with defined MeSH terminology, an electronic search was conducted from the following databases: Medline, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews and Scopus. Abstracts of various professional society meetings were also screened and hand searching of various reviews and guideline articles was carried out. The full text of 52 articles were reviewed, from which 5 articles satisfied the inclusion/exclusion criteria for effectiveness and immunogenicity trials and 1 article was included for safety data. Jadad score was used to assess the quality of included studies. The results of the included studies were inconsistent, and the studies were generally of suboptimal methodological quality. Most of the included studies (n = 3) investigated the use of more than one vaccine, however not all commonly used vaccines in HCT were investigated. None of the studies reported any long-term benefits for HCT recipients of vaccinated donors. Only one study reported safety data of using vaccination in donors. Given the suboptimal quality of the studies, and questionable effectiveness, donor vaccination cannot be recommended for all. Prospective high-quality vaccine trials in HCT donors are needed.

Immunizations in solid organ and hematopoeitic stem cell transplant patients: A comprehensive review

The Solid Organ Transplantation (SOT) and Haematopoietic Stem Cell Transplantation (HSCT) population is continuously increasing as a result of broader indications for transplant and improved survival. Infectious diseases, including vaccine-preventable diseases, are a significant threat for this population, primarily after but also prior to transplantation. As a consequence, clinicians must ensure that patients are optimally immunized before transplantation, to provide the best protection during the early post-transplantation period, when immunosuppression is the strongest and vaccine responses are poor. After 3-6 months, inactivated vaccines immunization can be resumed. By contrast, live-attenuated vaccines are lifelong contraindicated in SOT patients, but can be considered in HSCT patients at least 2 years after transplantation, if there is no immunosuppression or graft-versus-host-disease. However, because of the advantages of live-attenuated over inactivated vaccines--and also sometimes the absence of an inactivated alternative--an increasing number of prospective studies on live vaccine immunization after transplantation are performed and give new insights about safety and immunogenicity in this population.

Vaccinations in patients with hematological malignancies

Patients with hematological malignancies are at risk for a number of infections that are potentially preventable by vaccinations such as pneumococcal infections and influenza. Treatment, especially with anti-B-cell antibodies and hematopoietic stem cell transplantation (HSCT), negatively impacts the response to vaccination for several months. It is therefore recommended that patients be vaccinated before initiating immunosuppressive therapy if possible. The risk of side-effects with inactivated vaccines is low, but care has to be taken with live vaccines, such as varicella-zoster virus vaccine, since severe and fatal complications have been reported. HSCT patients require repeated doses of most vaccines to achieve long-lasting immune responses. New therapeutic options for patients with hematological malignancies that are rapidly being introduced into clinical practice will require additional research regarding the efficacy of vaccinations. New vaccines are also in development that will require well-designed studies to ascertain efficacy and safety.

Immunogenicity, safety, and tolerability of 13-valent pneumococcal conjugate vaccine followed by 23-valent pneumococcal polysaccharide vaccine in recipients of allogeneic hematopoietic stem cell transplant aged ≥2 years: an open-label study

Severe Streptococcus pneumoniae infections are frequent complications after hematopoietic stem cell transplant (HSCT). A 3-dose regimen of 13-valent pneumococcal conjugate vaccine, starting 3–6 months after HSCT and followed by a booster dose, may be required for adequate protection.

Background. Life-threatening Streptococcus pneumoniae infections often occur after hematopoietic stem cell transplant (HSCT); vaccination is important for prevention.

Methods. In an open-label study, patients (n = 251) 3–6 months after allogeneic HSCT received 3 doses of 13-valent pneumococcal conjugate vaccine (PCV13) at 1-month intervals, a fourth dose 6 months later, and 1 dose of 23-valent pneumococcal polysaccharide vaccine (PPSV23) 1 month later. Immunogenicity at prespecified time points and vaccine safety were assessed.

Results. In the evaluable immunogenicity population (N = 216; mean age, 37.8 years), geometric mean fold rises (GMFRs) of immunoglobulin G geometric mean concentrations from baseline to postdose 3 showed significant increases in antibody levels across all PCV13 serotypes (GMFR range, 2.99–23.85; 95% confidence interval lower limit, >1); there were significant declines over the next 6 months, significant increases from predose 4 to postdose 4 (GMFR range, 3.00–6.97), and little change after PPSV23 (GMFR range, 0.86–1.12). Local and systemic reactions were more frequent after dose 4. Six patients experienced serious adverse events possibly related to PCV13 (facial diplegia, injection-site erythema and pyrexia, autoimmune hemolytic anemia, and suspected lack of vaccine efficacy after dose 3 leading to pneumococcal infection), PCV13 and PPSV23 (Guillain-Barré syndrome), or PPSV23 (cellulitis). There were 14 deaths, none related to study vaccines.

Conclusions. A 3-dose PCV13 regimen followed by a booster dose may be required to protect against pneumococcal disease in HSCT recipients. Dose 4 was associated with increased local and systemic reactions, but the overall safety profile of a 4-dose regimen was considered acceptable.

Clinical Trials Registration. NCT00980655.

Long-term persistence of the immune response to antipneumococcal vaccines after Allo-SCT: 10-year follow-up of the EBMT-IDWP01 trial

The guidelines for immunization of hematopoietic SCT (HSCT) recipients recommend three doses of antipneumococcal conjugate vaccine (PCV) from 3 to 6 months after transplant, followed by a dose of polysaccharide 23-valent (PPV23) vaccine at 12 months in the case of no GVHD or an additional PCV dose in the case of GVHD. Due to the lack of long-term data in the literature, there is no recommendation for boosts after 12 months. Our goal was to assess the maintenance of the immune response to pneumococcal vaccines in patients vaccinated 10 years ago according to current guidelines. Thirty surviving patients of the IDWP01 (Infectious Diseases Working Party 1) trial were assessed for antibody levels against the seven antigens of the PCV7 and against two of the PPV23-specific antigens. When compared with 24 months after transplant, the immune response did not significantly decrease but with important serotype-specific variability. There was no evidence that an additional dose of PPV23 given to 11/30 patients 2-11 years after transplant was beneficial. In long-term HSCT survivors with no or few GVHD vaccinated against Streptococcus pneumoniae according to the current guidelines, the specific immunity is not fully maintained a decade later. The optimal schedule of antipneumococcal vaccination in HSCT recipients after 12 months remains to be established.

Pretransplant vaccinations in allogeneic stem cell transplantation donors and recipients: an often-missed opportunity for immunoprotection?

Immune deficiency following hematopoietic cell transplantation predisposes the patient to potentially deadly infections. Vaccinations can improve immunity and thus reduce the morbidity and mortality associated with these infections. Over the years different sets of guidelines have been published the most recent by the Infectious Diseases Society of American (IDSA). There is limited evidence that vaccination of donors and/or recipients before transplantation may improve immunity. However, despite the possibility of augmented immunity, there remain logistical, ethical and medical concerns about such a vaccination strategy.

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.

Immunization in cancer patients: where we stand

An increasing proportion of cancer patients benefit from new treatment strategies. However, infection remains a main cause of morbidity and mortality, either due to the underlying diseases, to treatment, or both. Although most opportunistic infections are sofar not routinely preventable by vaccines, community infections such as invasive pneumococcal disease and influenza may be avoided by vaccines in many instances. The immune response of cancer patients to vaccines is almost constantly depressed when compared to the one of healthy individuals of the same age range. However, they may, in many cases, reach seroprotection. This article addresses the rationale to develop and implement immunization programs in cancer patients, including patients with hematologic malignancies and recipients of stem cell transplantation, and the main specificities of this patient population regarding vaccines, and the potential approaches to improve the immune response. The Infectious Diseases Society of America has recently published guidelines for vaccination of the immunocompromised hosts. Although many questions remain to be clarified, oncologists and hematologists should be encouraged to implement these guidelines in their therapeutic programs and to develop prospective studies covering unsolved issues.

Pneumococcal immunization in immunocompromised hosts: where do we stand?

Immunocompromised patients are all at risk of invasive pneumococcal disease, of different degrees and timings. However, considerable progress in pneumococcal immunization over the last 30 years should benefit these patients. The 23-valent polysaccharide vaccine has been widely evaluated in these populations, but due to its low immunogenicity, its efficacy is sub-optimal, or even low. The principle of the conjugate vaccine is that, through the protein conjugation with the polysaccharide, the vaccine becomes more immunogenic, T-cell dependent, and thus providing a better early response and a boost effect. The 7-valent conjugate vaccine has been the first one to be evaluated in different immunocompromised populations. We review here the efficacy and safety of the different antipneumococcal vaccines in cancer, transplant and HIV-positive patients and propose a critical appraisal of the current guidelines.

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.

Use of the 13-valent pneumococcal conjugate vaccine in children and adolescents aged 6 - 17 years

INTRODUCTION

The introduction of pneumococcal conjugate vaccines into infant immunization schedules has successfully reduced the incidence of pneumococcal disease caused by vaccine serotypes. Disease incidence is low in healthy 6 - 17-year-old children and young people; however, there are a number of clinical conditions that put individuals in this age group at increased risk. Expansion of the license of a 13-valent pneumococcal conjugate vaccine , PCV-13, to include the 6 - 17 age group has recently been approved by European and American regulatory bodies.

AREAS COVERED

Studies assessing the safety, immunogenicity, and efficacy of pneumococcal conjugate vaccines in both healthy and high-risk 6 - 17-year-old children and adolescents are covered and the potential impact of PCV-13 in these populations is discussed. The use of the 23-valent pneumococcal polysaccharide vaccine, PPV-23, in high-risk children and adolescents is also considered.

EXPERT OPINION

Expanding the use of PCV-13 to include high-risk children and adolescents aged 6 - 17 has the potential to prevent additional cases of disease; however, vaccination of this population may no longer be necessary when herd immunity to PCV-13 serotypes becomes fully established. Despite the broader serotype coverage of PPV-23, the benefits of this vaccine in high-risk populations are uncertain.

Immune reconstitution after combined haploidentical and umbilical cord blood transplant

Umbilical cord blood (UCB) stem cells are frequently employed for allogeneic stem cell transplant, but delayed myeloid and lymphoid immune reconstitution leads to increased risk of infections. We recently reported the clinical results of 45 patients enrolled on a pilot study combining UCB with a human leukocyte antigen (HLA)-haploidentical donor with reduced-intensity conditioning who showed rapid neutrophil and platelet recovery. We report here preliminary immune reconstitution data of these patients. Patients were assessed for lymphocyte subsets, T-cell diversity, Cylex ImmuKnow assay and serological response to pneumococcal vaccination. Natural killer (NK)-cell and B-cell reconstitution were rapid at 1 month and 3 months, respectively. T-cell recovery was delayed, with a gradual increase in the number of T-cells starting around 6 months post-transplant, and was characterized by a diverse polyclonal T-cell repertoire. Overall, immune reconstitution after haplo-cord transplant is similar to that seen after cord blood transplant, despite infusion of much lower cord blood cell dose.

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.

Neoantigen and tumor antigen-specific immunity transferred from immunized donors is detectable early after allogeneic transplantation in myeloma patients

To enhance the therapeutic index of allogeneic hematopoietic SCT (HSCT), we immunized 10 HLA-matched sibling donors before stem cell collection with recipient-derived clonal myeloma Ig, idiotype (Id), as a tumor antigen, conjugated with keyhole limpet hemocyanin (KLH). Vaccinations were safe in donors and recipients. Donor-derived KLH- and Id-specific humoral and central and effector memory T-cell responses were detectable by day 30 after HSCT and were boosted by post-transplant vaccinations at 3 months in most recipients. One patient died before booster vaccinations. Specifically, after completing treatment, 8/9 myeloma recipients had persistent Id-specific immune responses and 5/9 had improvement in disease status. Although regulatory T cells increased after vaccination, they did not impact immune responses. At a median potential follow-up period of 74 months, 6 patients are alive, the 10 patients have a median PFS of 28.5 months and median OS has not been reached. Our results provide proof of principle that neoantigen and tumor antigen-specific humoral and cellular immunity could be safely induced in HSCT donors and passively transferred to recipients. This general strategy may be used to reduce relapse of malignancies and augment protection against infections after allogeneic HSCT.

Vaccination recommendations for the hematology and oncology and post-stem cell transplant populations

Vaccination is a simple yet important process used to prevent many infections in the general population. For patients with suppressed immune systems, especially those who are undergoing chemotherapy or who have undergone stem cell transplant, repeat vaccination or boosters may be crucial in prolonging and/or extending immunity. The purpose of this review is to examine the need for each vaccine in two separate oncology populations: patients receiving concurrent chemotherapy and post-stem cell transplant patients. In addition, the importance of avoiding live vaccines and criteria for reconsideration at a future time will also be discussed.

NCI, NHLBI/PBMTC first international conference on late effects after pediatric hematopoietic cell transplantation: persistent immune deficiency in pediatric transplant survivors

Defective immune reconstitution is a major barrier to successful hematopoietic cell transplantation (HCT), and has important implications in the pediatric population. There are many factors that affect immune recovery, including stem cell source and graft-versus-host disease (GVHD). Complete assessment of immune recovery, including T and B lymphocyte evaluation, innate immunity, and response to neoantigens, may provide insight as to infection risk and optimal time for immunizations. The increasing use of cord blood grafts requires additional study regarding early reconstitution and impact upon survival. Immunization schedules may require modification based upon stem cell source and immune reconstitution, and this is of particular importance as many children have been incompletely immunized, or not at all, before school entry. Additional studies are needed in children post-HCT to evaluate the impact of differing stem cell sources upon immune reconstitution, infectious risks, and immunization responses.

Evaluation of current cancer immunotherapy: hemato-oncology

Hematologic malignancies were the first diseases in clinical oncology for which the potential of harnessing the immune system as targeted therapy was unequivocally demonstrated. Unfortunately, the use of this highly efficacious modality has been limited to only a subset of patients and diseases because of immune-mediated toxicities resulting from incomplete specificity, and disease-specific determinants of sensitivity versus resistance to immune effector mechanisms. Recent studies, however, have begun to elucidate the molecular basis of the observed clinical effects allowing the rational development of next generation of immunotherapeutic combinations. We discuss here cancer antigen targets in hematologic malignancies and the specific approaches to induce immunity being pursued, the importance of modulating the host immunoregulatory environment, and the special features of immunological monitoring in clinical investigation. The hematologic malignancies represent an ideal setting for the development of immunotherapy due to logistical, clinical monitoring, and disease biology factors and may represent an exemplar for immune-based treatment in other cancer types.

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.

A randomized clinical trial comparing revaccination with pneumococcal conjugate vaccine to polysaccharide vaccine among HIV-infected adults

BACKGROUND

The risk of pneumococcal disease persists, and antibody responses to revaccination with the 23-valent polysaccharide vaccine (PPV) are low among human immunodeficiency virus (HIV)-infected adults. We determined whether revaccination with the 7-valent pneumococcal conjugate vaccine (PCV) would enhance these responses.

METHODS

In a randomized clinical trial, we compared the immunogenicity of revaccination with PCV ( n = 131) or PPV (n = 73) among HIV-infected adults (median CD4 cell count, 533 cells/mm(3)) who had been vaccinated with PPV 3-8 years earlier. HIV-uninfected adults (n = 25) without prior pneumococcal vaccination received 1 dose of PCV. A positive response was defined as a >or=2-fold increase (from baseline to day 60) in capsule-specific immunoglobulin G, with a postvaccination level >or=1000 ng/mL for at least 2 of the 4 serotypes.

RESULTS

HIV-infected persons demonstrated a higher frequency of positive antibody responses to PCV than to PPV (57% vs 36%) (P = .004) and greater mean changes in the immunoglobulin G concentration from baseline to day 60 for serotypes 4, 9V, and 19F (P < .05, for all), but not for serotype 14. However, by day 180, both outcomes were similar. Responses to PCV were greater in frequency and magnitude for all serotypes in HIV-uninfected adults, compared with those in HIV-infected adults.

CONCLUSIONS

Among persons with HIV infection, revaccination with PCV was only transiently more immunogenic than PPV, and responses were inferior to those in HIV-uninfected subjects with primary vaccination. Pneumococcal vaccines with more robust and sustained immunogenicity are needed for HIV-infected adults. Clinical trial registration. ClinicalTrials.gov identifier NCT00622843.

Response to pneumococcal (PNCRM7) and haemophilus influenzae conjugate vaccines (HIB) in pediatric and adult recipients of an allogeneic hematopoietic cell transplantation (alloHCT)

Young children and allogeneic hematopoietic cell transplantation (HCT) recipients respond poorly to polysaccharide antigens, rendering them susceptible to severe infections because of encapsulated bacteria. This study evaluated the responses of 127 HCT patients, median age 23.0 years, vaccinated with PNCRM7 and Haemophilus influenzae (HIB) conjugate, 2 conjugate vaccines highly immunogenic in healthy children. Median time to vaccination was 1.1 years after HCT. Sixty-two percent of patients responded to PNCRM7 (45 of 51 children, 34 of 76 adults, P < .001). Overall response to HIB was 86%, including 77% of PNCRM7 nonresponders. Although PNCRM7 response was adversely affected by older age (P < .001), individuals > or =50 years old responded significantly better if vaccinated following acquisition of specific minimal milestones of immune competence, CD4 >200/microL, IgG >500 mg/dL, PHA within 60% lower limit of normal (11 of 19 versus 0 of 8, P < .006). A similar trend was observed in patients with limited chronic graft-versus-host disease (cGVHD). In all patients, higher levels of circulating CD4(+)CD45RA cells correlated with improved PNCRM7 response. These data demonstrate that PNCRM7 is immunogenic in allogeneic HCT patients, including older adults, but suggest that vaccination at fixed intervals after HCT, irrespective of immune competence, may limit its effectiveness. Prospective, multicenter trials assessing the best strategy to administer this vaccine and its impact on pneumococcal infections following transplantation are warranted.

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.