Evaluation of Immune Responses to Seasonal Influenza Vaccination in Healthy Volunteers and in Patients After Stem Cell Transplantation

Immunogenicity and Tolerance of BNT162b2 mRNA Vaccine in Allogeneic Hematopoietic Stem Cell Transplant Patients

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (ASCT) induces acquired immunodeficiency, potentially altering vaccine response. Herein, we aimed to explore the clinical tolerance and the humoral and cellular immune responses following anti-SARS-CoV-2 vaccination in ASCT recipients.

METHODS

A prospective, non-randomized, controlled study that involved 43 ASCT subjects and 31 healthy controls. Humoral response was investigated using the Elecsys® test anti-SARS-CoV-2. Cellular response was assessed using the QFN® SARS-CoV-2 test. The lymphocyte cytokine profile was tested using the LEGENDplex™ HU Th Cytokine Panel Kit (12-plex).

RESULTS

Adverse effects (AE) were observed in 69% of patients, encompassing pain at the injection site, fever, asthenia, or headaches. Controls presented more side effects like pain in the injection site and asthenia with no difference in the overall AE frequency. Both groups exhibited robust humoral and cellular responses. Only the vaccine transplant delay impacted the humoral response alongside a previous SARS-CoV-2 infection. Noteworthily, controls displayed a Th1 cytokine profile, while patients showed a mixed Th1/Th2 profile.

CONCLUSIONS

Pfizer-BioNTech® anti-SARS-CoV-2 vaccination is well tolerated in ASCT patients, inducing robust humoral and cellular responses. Further exploration is warranted to understand the impact of a mixed cytokine profile in ASCT patients.

Robust immunity to influenza vaccination in haematopoietic stem cell transplant recipients following reconstitution of humoral and adaptive immunity

Objectives

Influenza causes significant morbidity and mortality, especially in high-risk populations. Although current vaccination regimens are the best method to combat annual influenza disease, vaccine efficacy can be low in high-risk groups, such as haematopoietic stem cell transplant (HSCT) recipients.

Methods

We comprehensively assessed humoral immunity, antibody landscapes, systems serology and influenza-specific B-cell responses, together with their phenotypes and isotypes, to the inactivated influenza vaccine (IIV) in HSCT recipients in comparison to healthy controls.

Results

Inactivated influenza vaccine significantly increased haemagglutination inhibition (HAI) titres in HSCT recipients, similar to healthy controls. Systems serology revealed increased IgG1 and IgG3 antibody levels towards the haemagglutinin (HA) head, but not to neuraminidase, nucleoprotein or HA stem. IIV also increased frequencies of total, IgG class-switched and CD21^loCD27⁺ influenza-specific B cells, determined by HA probes and flow cytometry. Strikingly, 40% of HSCT recipients had markedly higher antibody responses towards A/H3N2 vaccine strain than healthy controls and showed cross-reactivity to antigenically drifted A/H3N2 strains by antibody landscape analysis. These superior humoral responses were associated with a greater time interval after HSCT, while multivariant analyses revealed the importance of pre-existing immune memory. Conversely, in HSCT recipients who did not respond to the first dose, the second IIV dose did not greatly improve their humoral response, although 50% of second-dose patients reached a seroprotective HAI titre for at least one of vaccine strains.

Conclusions

Our study demonstrates efficient, although time-dependent, immune responses to IIV in HSCT recipients, and provides insights into influenza vaccination strategies targeted to immunocompromised high-risk groups.

Third BNT162b2 mRNA SARS-CoV-2 Vaccine Dose Significantly Enhances Immunogenicity in Recipients of Allogeneic Hematopoietic Stem Cell Transplantation

COVID-19-related mortality among hematopoietic stem cell transplantation (HSCT) recipients in the pre-vaccine era ranged between 22 and 33%. The Pfizer/BioNTech BNT162b2 vaccine demonstrated significant immunogenicity and efficacy in the healthy population; however, its long-term effects on allogeneic HSCT recipients remained unclear. Our study longitudinally evaluated humoral and cellular responses to the BNT162b2 vaccine in adult allogeneic HSCT patients. A positive response was defined as antibody titers ≥ 150 AU/mL post-second vaccination. Among 77 included patients, 51 (66.2%) responded to vaccination. Response-associated factors were female gender, recent anti-CD20 therapy, and a longer interval between transplant and vaccination. Response rates reached 83.7% in patients vaccinated >12 months post-transplant. At 6 months post-second vaccination, antibody titers dropped, but were significantly increased with the booster dose. Moreover, 43% (6/14) of non-responders to the second vaccination acquired sufficient antibody titers after booster administration, resulting in an overall response rate of 79.5% for the entire cohort. The BNT162b2 vaccine was effective in allogeneic transplant recipients. Although antibody titers decreased with time, the third vaccination led to their significant elevation, with 93% of third-dose responders maintaining titers above 150 AU/mL at 3 months post-administration.

Lessons learnt from influenza vaccination in immunocompromised children undergoing treatment for cancer

Influenza infection contributes substantially to global morbidity and mortality, with children undergoing treatment for cancer among the most vulnerable due to immunosuppression associated with disease and treatment. However, influenza remains one of the most common vaccine-preventable diseases. Despite international guidelines recommending inactivated influenza vaccination on the basis of data supporting efficacy and an excellent safety profile in this population, uptake has often been suboptimal due to persisting hesitancy among both patients and oncologists regarding the ability of the vaccine to mount a sufficient immune response, the optimal vaccine schedule and timing, and the best method to assess response in immunocompromised populations. In this Review, we discuss the evidence regarding influenza vaccination in children with cancer, factors that influence response, and highlight strategies to optimise vaccination. Host immune factors play a substantial role, thus principles learnt from influenza vaccination can be broadly applied for the use of inactivated vaccines in children with cancer.

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.

SARS-CoV-2-reactive antibody detection after SARS-CoV-2 vaccination in hematopoietic stem cell transplant recipients: Prospective survey from the Spanish Hematopoietic Stem Cell Transplantation and Cell Therapy Group

This is a multicenter prospective observational study that included a large cohort (n = 397) of allogeneic (allo‐HSCT; (n = 311) and autologous (ASCT) hematopoietic stem cell transplant (n = 86) recipients who were monitored for antibody detection within 3–6 weeks after complete severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) vaccination from February 1, 2021, to July 20, 2021. Most patients (n = 387, 97.4%) received mRNA‐based vaccines. Most of the recipients (93%) were vaccinated more than 1 year after transplant. Detectable SARS‐CoV‐2‐reactive antibodies were observed in 242 (78%) of allo‐HSCT and in 73 (85%) of ASCT recipients. Multivariate analysis in allo‐HSCT recipients identified lymphopenia < 1 × 10⁹/ml (odds ratio [OR] 0.33, 95% confidence interval [95% CI] 0.16–0.69, p = .003), active graft versus host disease (GvHD; OR 0.51, 95% CI 0.27–0.98, p = .04) and vaccination within the first year of transplant (OR 0.3, 95% CI 0.15–0.9, p = .04) associated with lower antibody detection whereas. In ASCT, non‐Hodgkin's lymphoma (NHL; OR 0.09, 95% CI 0.02–0.44, p = .003) and active corticosteroid therapy (OR 0.2, 95% CI 0.02–0.87, p = .03) were associated with lower detection rate. We report an encouraging rate of SARS‐CoV‐2‐reactive antibodies detection in these severe immunocompromised patients. Lymphopenia, GvHD, the timing of vaccine, and NHL and corticosteroids therapy should be considered in allo‐HSCT and ASCT, respectively, to identify candidates for SARS‐CoV‐2 antibodies monitoring.

Vaccine Responses in Adult Hematopoietic Stem Cell Transplant Recipients: A Comprehensive Review

Simple Summary

Patients who recently received a stem cell transplantation are at greater risk for infection due to impairment of their immune system. In order to prevent severe infection, these patients are vaccinated after their stem cell transplantation with childhood immunization vaccines. Timing of this vaccination is important in order to be effective and obtain proper immune response. Postponement of vaccination would lead to better immune response but would also cause longer-lasting risk of infection. This review describes available data on the timing of vaccination and its vaccine responses. Optimal timing of vaccination might require an individualized approach per patient.

Abstract

Consensus on timing of post-hematopoietic stem cell transplantation (HSCT) vaccination is currently lacking and is therefore assessed in this review. PubMed was searched systematically for articles concerning vaccination post-HSCT and included a basis in predefined criteria. To enable comparison, data were extracted and tables were constructed per vaccine, displaying vaccine response as either seroprotection or seroconversion for allogeneic HSCT (alloHSCT) and autologous HSCT (autoHSCT) separately. A total of 33 studies were included with 1914 patients in total: 1654 alloHSCT recipients and 260 autoHSCT recipients. In alloHSCT recipients, influenza vaccine at 7–48 months post-transplant resulted in responses of 10–97%. After 12 months post-transplant, responses were >45%. Pneumococcal vaccination 3–25 months post-transplant resulted in responses of 43–99%, with the response increasing with time. Diphtheria, tetanus, pertussis, poliomyelitis and Haemophilus influenzae type b at 6–17 months post-transplant: 26–100%. Meningococcal vaccination at 12 months post-transplant: 65%. Hepatitis B vaccine at 6–23 months post-transplant: 40–94%. Measles, mumps and rubella at 41–69 months post-transplant: 19–72%. In general, autoHSCT recipients obtained slightly higher responses compared with alloHSCT recipients. Conclusively, responses to childhood immunization vaccines post-HSCT are poor in comparison with healthy individuals. Therefore, evaluation of response might be indicated. Timing of revaccination is essential for optimal response. An individualized approach might be necessary for optimizing vaccine responses.

Spanish Society of Hematology and Hemotherapy expert consensus opinion for SARS-CoV-2 vaccination in onco-hematological patients

In the midst of the COVID-19 pandemic, different vaccines in front of SARS-CoV-2 have been approved and administered in different vulnerable populations. As patients with cancer were excluded from pivotal trials of vaccination, little is known on their immunogenic response to these vaccines, particularly in patients with severely impaired immune system. In response to that uncertainty, the Spanish Society of Hematology and Hemotherapy launched an initiative aimed to provide recommendations for vaccination of the main hematological conditions. This document is based on the available information on COVID-19 outcomes, prior knowledge on vaccination in hematological patients, recent published data on serological response in oncohematological patients and expert opinions. New information about SARS-CoV-2 vaccination will be gathered in the near future, providing new scientific grounds to delineate the most adequate management of vaccination in patients with hematological diseases. The current limited data on SARS-CoV-2 vaccines in hematological patients represents a major limitation of this expert consensus opinion. In fact, the speed in which this field evolves may reduce their validity in the near future.

B-Cell Immunophenotyping to Predict Vaccination Outcome in the Immunocompromised - A Systematic Review

Vaccination is the most effective measure to prevent infections in the general population. Its efficiency strongly depends on the function and composition of the immune system. If the immune system lacks critical components, patients will not be fully protected despite a completed vaccination schedule. Antigen-specific serum immunoglobulin levels are broadly used correlates of protection. These are the products of terminally differentiated B cells - plasma cells. Here we reviewed the literature on how aberrancies in B-cell composition and function influence immune responses to vaccinations. In a search through five major literature databases, 6,537 unique articles published from 2000 and onwards were identified. 75 articles were included along three major research lines: extremities of life, immunodeficiency and immunosuppression. Details of the protocol can be found in the International Prospective Register of Systematic Reviews [PROSPERO (registration number CRD42021226683)]. The majority of articles investigated immune responses in adults, in which vaccinations against pneumococci and influenza were strongly represented. Lack of baseline information was the most common reason of exclusion. Irrespective of study group, three parameters measured at baseline seemed to have a predictive value in assessing vaccine efficacy: (1) distribution of B-cell subsets (mostly a reduction in memory B cells), (2) presence of exhausted/activated B cells, or B cells with an aberrant phenotype, and (3) pre-existing immunological memory. In this review we showed how pre-immunization (baseline) knowledge of circulating B cells can be used to predict vaccination efficacy. We hope that this overview will contribute to optimizing vaccination strategies, especially in immunocompromised patients.

Association of host factors with antibody response to seasonal influenza vaccination in allogeneic hematopoietic stem cell transplant (HSCT) patients

BACKGROUND

Influenza vaccination efficacy is reduced after hematopoietic stem cell transplantation (HSCT) and patient factors determining vaccination outcomes are still poorly understood.

METHODS

We investigated the antibody response to seasonal influenza vaccination in 135 HSCT patients and 69 healthy volunteers (HVs) in a prospective observational multicenter cohort study. We identified patient factors associated with hemagglutination inhibition titers against A/California/2009/H1N1, A/Texas/2012/H3N2, and B/Massachusetts/2012 by multivariable regression on the observed titer levels and on seroconversion/seroprotection categories for comparison.

RESULTS

Both regression approaches yield consistent results but regression on titers estimated associations with higher precision. HSCT patients required two vaccine doses to achieve average responses comparable to a single dose in HVs. Pre-vaccination titers were positively associated with time after transplantation, confirming that HSCT patients can elicit potent antibody responses. However, an unrelated donor, absolute lymphocyte counts below the normal range and treatment with calcineurin inhibitors lower the odds of responding.

CONCLUSIONS

HSCT patients show a highly heterogeneous vaccine response, but overall, patients benefited from the booster shot and can acquire seroprotective antibodies over the years after transplantation. Several common patient factors lower the odds of responding, urging to identify additional preventive strategies in the poorly responding groups.

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.

Safety and Immunogenicity of the BNT162b2 mRNA COVID-19 Vaccine in Patients after Allogeneic HCT or CD19-based CART therapy-A Single-Center Prospective Cohort Study

Data are scarce regarding both the safety and immunogenicity of the BNT162b2 mRNA COVID-19 vaccine in patients undergoing immune cell therapy; thus, we prospectively evaluated these two domains in patients receiving this vaccine after allogeneic hematopoietic cell transplantation (HCT; n = 66) or after CD19-based chimeric antigen receptor T cell (CART) therapy (n = 14). Overall, the vaccine was well tolerated, with mild non-hematologic vaccine-reported adverse events in a minority of the patients. Twelve percent of the patients after the first dose and 10% of the patients after the second dose developed cytopenia, and there were three cases of graft-versus-host disease exacerbation after each dose. A single case of impending graft rejection was summarized as possibly related. Evaluation of immunogenicity showed that 57% of patients after CART infusion and 75% patients after allogeneic HCT had evidence of humoral and/or cellular response to the vaccine. The Cox regression model indicated that longer time from infusion of cells, female sex, and higher CD19⁺ cells were associated with a positive humoral response, whereas a higher CD4⁺/CD8⁺ ratio was correlated with a positive cellular response, as confirmed by the ELISpot test. We conclude that the BNT162b2 mRNA COVID-19 vaccine has impressive immunogenicity in patients after allogeneic HCT or CART. Adverse events were mostly mild and transient, but some significant hematologic events were observed; hence, patients should be closely monitored.

A randomised trial of two 2-dose influenza vaccination strategies for patients following autologous haematopoietic stem cell transplantation

BACKGROUND

Seroprotection and seroconversion rates are not well understood for 2-dose inactivated influenza vaccination (IIV) schedules in autologous haematopoietic stem cell transplantation (autoHCT) patients.

MATERIALS/METHODS

A randomised single-blind controlled trial of IIV in autoHCT patients in their first year post-transplant was conducted. Patients were randomised 1:1 to high dose (HD) IIV followed by standard dose (SD) vaccine (HD-SD arm) or two SD vaccines (SD-SD arm), 4 weeks apart. Haemagglutination inhibition (HI) assay for IIV strains was performed at baseline, 1, 2 and 6 months post-first dose. Evaluable primary outcomes were seroprotection (HI titre ≥40) and seroconversion (4-fold titre rise) rates and secondary outcomes: geometric mean titres (GMT), GMT ratios (GMR), adverse events, influenza-like-illness (ILI) and laboratory-confirmed influenza (LCI) rates and factors associated with seroconversion.

RESULTS

Sixty-eight patients were enrolled (34 per arm) with median age of 61.5 years, majority male (68%) with myeloma (68%). Median time from autoHCT to vaccination was 2.3 months. For HD-SD and SD-SD arms, percentage of patients achieving seroprotection was 75.8% and 79.4% for H1N1, 84.9% and 88.2% for H3N2 (all p>0.05) and 78.8% and 97.1% for influenza-B/Yamagata (p=0.03), respectively. Seroconversion rates, GMT and GMR, number of ILI or LCIs were not significantly different between arms. Adverse event rates were similar. Receipt of concurrent cancer therapy was independently associated with higher odds of seroconversion (OR 4.3, 95% CI 1.2-14.9, p=0.02).

CONCLUSIONS

High seroprotection and seroconversion rates against all influenza strains can be achieved with vaccination as early as 2 months post-autoHCT with either two-dose vaccine schedules.

Clinical Effectiveness of Influenza Vaccination After Allogeneic Hematopoietic Stem Cell Transplantation: A Cross-sectional, Prospective, Observational Study

BACKGROUND

Vaccination is the primary method for preventing influenza respiratory virus infection (RVI). Although the influenza vaccine is able to achieve serological responses in some allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients, its clinical benefits are still uncertain.

METHODS

In this prospective, cross-sectional study, we retrospectively analyzed the effect of inactivated trivalent influenza vaccination on the prevalence of influenza RVI in a consecutive cohort of 136 allo-HSCT adult recipients who developed 161 RVI over 5 flu seasons (from 2013 to 2018). Respiratory viruses in upper- and/or lower-respiratory tract specimens were tested using multiplex polymerase chain reaction panel assays.

RESULTS

Overall, we diagnosed 74 episodes (46%) of influenza RVI in 70 allo-HSCT recipients. Influenza RVI occurred in 51% of the non-vaccinated compared to 36% of the vaccinated recipients (P = .036). A multivariate analysis showed that influenza vaccination was associated with a lower prevalence of influenza RVI (odds ratio [OR] 0.39, P = .01). A multivariate risk factor analysis of lower-respiratory tract disease (LRTD) identified 2 conditions associated with the probability of influenza RVI progression: influenza vaccination (OR 0.12, 95% confidence interval [CI] 0.014-1, P = .05) and a high-risk immunodeficiency score (OR 36, 95% CI 2.26-575, P = .011). Influenza vaccination was also associated with a lower likelihood of an influenza-related hospital admission (14% vs 2%, P = .04).

CONCLUSIONS

This study shows that influenza vaccination may have a clinical benefit in allo-HSCT recipients with virologically-confirmed RVI, in terms of a lower influenza RVI prevalence, slower LRTD progression, and lower likelihood of hospital admission.

Immunogenicity of Inactivated Varicella Zoster Vaccine in Autologous Hematopoietic Stem Cell Transplant Recipients and Patients With Solid or Hematologic Cancer

Background

In phase 3 trials, inactivated varicella zoster virus (VZV) vaccine (ZV_IN) was well tolerated and efficacious against herpes zoster (HZ) in autologous hematopoietic stem cell transplant (auto-HSCT) recipients and patients with solid tumor malignancies receiving chemotherapy (STMc) but did not reduce HZ incidence in patients with hematologic malignancies (HMs). Here, we describe ZV_IN immunogenicity from these studies.

Methods

Patients were randomized to ZV_IN or placebo (4 doses). Immunogenicity was assessed by glycoprotein enzyme-linked immunosorbent assay (gpELISA) and VZV interferon (IFN)-γ enzyme-linked immunospot (ELISPOT) assay in patients receiving all 4 doses without developing HZ at the time of blood sampling.

Results

Estimated geometric mean fold rise ratios (ZV_IN/placebo) by gpELISA and IFN-y ELISPOT ~28 days post-dose 4 were 2.02 (95% confidence interval [CI], 1.53-2.67) and 5.41 (95% CI, 3.60-8.12) in auto-HSCT recipients; 1.88 (95% CI, 1.79-1.98) and 2.10 (95% CI, 1.69-2.62) in patients with STMc; and not assessed and 2.35 (95% CI, 1.81-3.05) in patients with HM.

Conclusions

ZV_IN immunogenicity was directionally consistent with clinical efficacy in auto-HSCT recipients and patients with STMc even though HZ protection and VZV immunity were not statistically correlated. Despite a lack of clinical efficacy in patients with HM, ZV_IN immunogenicity was observed in this population. Immunological results did not predict vaccine efficacy in these 3 populations.

Clinical trial registration

NCT01229267, NCT01254630.

[Functional immunoassays in the setting of infectious risk and immunosuppressive therapy of non-HIV immunocompromised patients]

The holistic approach of the human immune system is based on the study of its components collectively driving a functional response to an immunogenic stimulus. To appreciate a specific immune dysfunction, a condition is mimicked ex vivo and the immune response induced is assessed. The application field of such assays are broad and expanding, from the diagnosis of primary and secondary immunodeficiencies, immunotherapy for cancer to the management of patients at-risk for infections and vaccination. These assays are immune monitoring tools that may contribute to a personalised and precision medicine. The purpose of this review is to describe immune functional assays available in the setting of non-HIV acquired immune deficiency. First, we will address the use of theses assays in the diagnosis of opportunistic infections such as viral reactivation. Secondly, we will report the usefulness of these assays to assess vaccine efficacy and to manage immunosuppressive therapies.

Respiratory Viruses Cause Late Morbidity in Recipients of Hematopoietic Stem Cell Transplantation

Common respiratory viral infections (CRVIs) frequently complicate hematopoietic stem cell transplantation (HSCT). We conducted a retrospective, single-center, observational cohort study to determine the incidence of CRVI in patients who received an allogeneic (allo) or autologous (auto) HSCT at the Royal Adelaide Hospital between 2009 and 2017. The median follow-up was 8.9 and 4.5 years for auto- and allo-HSCT recipients, respectively. There were 149 CRVI episodes in 74 patients, with rhinovirus being the most commonly isolated virus (n = 81, 47%). The majority of CRVIs (113/149, 75.8%) occurred more than 100 days post-HSCT and 67% were diagnosed in the outpatient setting. There was evidence of lower respiratory tract infection (LRTI) in 45.6% (68/149) of CRVIs. On multivariate logistic regression analysis, coviral infections and cytomegalovirus viremia were independent risk factors for progression of CRVI to LRTI. Ten (6.7%) CRVI episodes resulted in admission to intensive care for ventilatory support and 8 (5.4%) patients died within 30 days of CRVI diagnosis. In our study, 10.4% of HSCT recipients experienced a CRVI post-transplant, primarily causing late morbidity and potentially mortality. Prevention with strict infection control practices, vaccination, and patient education is essential.

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.

Immunogenicity of the inactivated influenza vaccine in children who have undergone allogeneic haematopoietic stem cell transplant

Influenza vaccination is recommended for children following allogeneic haematopoietic stem cell transplant (HSCT), however there is limited evidence regarding its benefit. A prospective multicentre study was conducted to evaluate the immunogenicity of the inactivated influenza vaccine in children who have undergone HSCT compared with healthy age-matched controls. Participants were vaccinated between 2013 and 2016 according to Australian guidelines. Influenza-specific hemagglutinin inhibition antibody titres were performed prior to each vaccination and 4 weeks following the final vaccination. A nasopharyngeal aspirate for influenza was performed on participants that developed influenza-like illness. There were 86 children recruited; 43 who had undergone HSCT and 43 controls. For the HSCT group, seroprotection and seroconversion rates were 81.4% and 60.5% for H3N2, 41.9% and 32.6% for H1N1, and 44.2% and 39.5% for B strain respectively. There was a significant geometric mean fold increase to the H3N2 (GMFI 5.80, 95% CI 3.68–9.14, p < 0.001) and B (GMFI 3.44, 95% CI 2.36–5.00, p = 0.048) strains. Serological response was superior in age-matched controls to all vaccine strains. There were no serious adverse events following vaccination. For children who underwent HSCT, incidence of laboratory-proven influenza infection was 2.3%. Overall, this study provides evidence to support annual inactivated influenza vaccine administration to children following HSCT.

Respiratory Virus Infections of the Stem Cell Transplant Recipient and the Hematologic Malignancy Patient

Respiratory virus infections in hematologic stem cell transplant recipients and patients with hematologic malignancies are increasingly recognized as a cause of significant morbidity and mortality. The often overlapping clinical presentation makes molecular diagnostic strategies imperative for rapid diagnosis and to inform understanding of the changing epidemiology of each of the respiratory viruses. Most respiratory virus infections are managed with supportive therapy, although there is effective antiviral therapy for influenza. The primary focus should remain on primary prevention infection control procedures and isolation precautions, avoidance of ill contacts, and vaccination for influenza.

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.

A comparison of viral microneutralization and haemagglutination inhibition assays as measures of seasonal inactivated influenza vaccine immunogenicity in the first year after reduced intensity conditioning, lymphocyte depleted allogeneic haematopoietic stem cell transplant

Traditionally, immune response to influenza vaccines has been measured using the haemagglutination inhibition (HAI) assay. A broader repertoire of techniques including the sensitive viral microneutralization (VMN) assay is now recommended by the European Medicines Agency (EMA). Comparing HAI and VMN, we determined immune response to a trivalent 2015-2016 seasonal inactivated influenza vaccine (SIIV) administered to 28 recipients of allogeneic haematopoietic stem cell transplant (HSCT). Vaccination was within the first-year post-transplant at a median of 78.5 (24-363) days. The proportion of patients with baseline and post-vaccination HAI titres ≥ 1:40 were 28.6% and 25% for A(H1N1)pdm09, 14.3% at both timepoints for A(H3N2), and 32.1% and 25% for B(Phuket). Pre and Post-vaccination geometric mean titres(GMT) were higher by VMN than HAI for A(H1N1)pdm09 and A(H3N2), but lower for B(Phuket)(p=<0.05). Geometric mean ratios(GMR) of baseline and post-vaccination titres were similar by HAI and VMN(p > 0.05) for all components. A single seroconversion to A(H1N1) was detected by ELISA-VMN. None of patient age, lymphocyte count, days from transplant to vaccination, donor type, or graft-versus-host disease (GVHD) or immunosuppressive therapy (IST) at vaccination correlated with baseline or post-vaccination titres by either assay. This absence of seroresponse to SIIV in the first-year post HSCT highlights the need for novel immunogenic vaccination formulations and schedules in this high-risk population.

Vaccines in pediatric transplant recipients-Past, present, and future

Infections significantly impact outcomes for solid organ and hematopoietic stem cell transplantation in children. Vaccine-preventable diseases contribute to morbidity and mortality in both early and late posttransplant time periods. Several infectious diseases and transplantation societies have published recommendations and guidelines that address immunization in adult and pediatric transplant recipients. In many cases, pediatric-specific studies are limited in size or quality, leading to recommendations being based on adult data or mixed adult-pediatric studies. We therefore review the current state of evidence for selected immunizations in pediatric transplant recipients and highlight areas for future investigation. Specific attention is given to studies that enrolled only children.

Influenza vaccines in immunosuppressed adults with cancer

BACKGROUND

This is an update of the Cochrane review published in 2013, Issue 10.Immunosuppressed cancer patients are at increased risk of serious influenza-related complications. Guidelines, therefore, recommend influenza vaccination for these patients. However, data on vaccine effectiveness in this population are lacking, and the value of vaccination in this population remains unclear.

OBJECTIVES

To assess the effectiveness of influenza vaccine in immunosuppressed adults with malignancies. The primary review outcome is all-cause mortality, preferably at the end of the influenza season. Influenza-like illness (ILI, a clinical definition), confirmed influenza, pneumonia, any hospitalisations, influenza-related mortality and immunogenicity were defined as secondary outcomes.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase and LILACS databases up to May 2017. We searched the following conference proceedings: ICAAC, ECCMID, IDSA (infectious disease conferences), ASH, ASBMT, EBMT (haematological), and ASCO (oncological) between the years 2006 to 2017. In addition, we scanned the references of all identified studies and pertinent reviews. We searched the websites of the manufacturers of influenza vaccine. Finally, we searched for ongoing or unpublished trials in clinical trial registry databases.

SELECTION CRITERIA

Randomised controlled trials (RCTs), prospective and retrospective cohort studies and case-control studies were considered, comparing inactivated influenza vaccines versus placebo, no vaccination or a different vaccine, in adults (16 years and over) with cancer. We considered solid malignancies treated with chemotherapy, haematological cancer patients treated or not treated with chemotherapy, cancer patients post-autologous (up to six months after transplantation) or allogeneic (at any time) haematopoietic stem cell transplantation (HSCT).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the risk of bias and extracted data from included studies adhering to Cochrane methodology. Meta-analysis could not be performed because of different outcome and denominator definitions in the included studies.

MAIN RESULTS

We identified six studies with a total of 2275 participants: five studies comparing vaccination with no vaccination, and one comparing adjuvanted vaccine with non-adjuvanted vaccine. Three studies were RCTs, one was a prospective observational cohort study and two were retrospective cohort studies.For the comparison of vaccination with no vaccination we included two RCTs and three observational studies, including 2202 participants. One study reported results in person-years while the others reported results per person. The five studies were performed between 1993 and 2015 and included adults with haematological diseases (three studies), patients following bone marrow transplantation (BMT) (two studies) and solid malignancies (three studies).One RCT and two observational studies reported all-cause mortality; the RCT showed similar mortality rates in both arms (odds ratio (OR) 1.25 (95% CI 0.43 to 3.62; 1 study, 78 participants, low-certainty evidence)); and the observational studies demonstrated a significant association between vaccine receipt and lower risk of death, adjusted hazard ratio 0.88 (95% CI 0.78 to 1; 1 study, 1577 participants, very low-certainty evidence) in one study and OR 0.42 (95% CI 0.24 to 0.75; 1 study, 806 participants, very low-certainty evidence) in the other. One RCT reported a reduction in ILI with vaccination, while no difference was observed in one observational study. Confirmed influenza rates were lower with vaccination in one RCT and the three observational studies, the difference reaching statistical significance in one. Pneumonia was observed significantly less frequently with vaccination in one observational study, but no difference was detected in another or in the RCT. One RCT showed a reduction in hospitalisations following vaccination, while an observational study found no difference. No life-threatening or persistent adverse effects from vaccination were reported. The strength of evidence was limited by the low number of included studies and by their low methodological quality and the certainty of the evidence for the mortality outcome according to GRADE was low to very low.For the comparison of adjuvanted vaccine with non-adjuvanted vaccine, we identified one RCT, including 73 patients. No differences were found for the primary and all secondary outcomes assessed. Mortality risk ratio was 0.54 (95% CI 0.05 to 5.73; low-certainty evidence) in the adjuvanted vaccine group. The quality of evidence was low due to the small sample size and the large confidence intervals for all outcomes.

AUTHORS' CONCLUSIONS

Observational data suggest lower mortality and infection-related outcomes with influenza vaccination. The strength of evidence is limited by the small number of studies and low grade of evidence. It seems that the evidence, although weak, shows that the benefits overweigh the potential risks when vaccinating adults with cancer against influenza. However, additional placebo or no-treatment controlled RCTs of influenza vaccination among adults with cancer is ethically questionable.There is no conclusive evidence regarding the use of adjuvanted versus non-adjuvanted influenza vaccine in this population.

A pilot randomized trial of adjuvanted influenza vaccine in adult allogeneic hematopoietic stem cell transplant recipients

The annual influenza vaccine is recommended for hematopoietic stem cell transplant (HSCT) patients although studies have shown suboptimal immunogenicity. Influenza vaccine containing an oil-in-water emulsion adjuvant (MF59) may lead to greater immunogenicity in HSCT recipients. We randomized adult allogeneic HSCT patients to receive the 2015-2016 influenza vaccine with or without MF59 adjuvant. Preimmunization and 4-week post-immunization sera underwent strain-specific hemagglutination inhibition assay. We randomized 73 patients and 67 (35 adjuvanted; 32 non-adjuvanted) had paired samples available at follow-up. Median age was 54 years (range 22-74) and time from transplant was 380 days (range 85-8107). Concurrent graft-versus-host disease was seen in 42/73 (57.5%). Geometric mean titers increased significantly after vaccination in both groups. Seroconversion to at least one of three influenza antigens was present in 62.9% vs 53.1% in adjuvanted vs non-adjuvanted vaccine (P=0.42). Factors associated with lower seroconversion rates were use of calcineurin inhibitors (P<0.001) and shorter duration from transplantation (P=0.001). Seroconversion rates were greater in patients who got previous year influenza vaccination (82.6% vs 45.5%, P=0.03). Adjuvanted vaccine demonstrated similar immunogenicity to non-adjuvanted vaccine in the HSCT population and may be an option for some patients.

Lower Respiratory Tract Diseases Caused by Common Respiratory Viruses among Stem Cell Transplantation Recipients: A Single Center Experience in Korea

PURPOSE

To describe the incidence, clinical courses, and risk factors for mortality of lower respiratory tract diseases (LRDs) caused by common respiratory viruses (CRVs) in stem cell transplantation (SCT) recipients.

MATERIALS AND METHODS

We retrospectively reviewed the medical records of 1038 patients who received SCT between January 2007 and August 2011 at a single center in Korea.

RESULTS

Seventy-one CRV-LRDs were identified in 67 (6.5%) patients. The human parainfluenza virus (HPIV) was the most common causative pathogen of CRV-LRDs at 100 days [cumulative incidence estimate, 23.5%; 95% confidence interval (CI), 3.3-43.7] and 1 year (cumulative incidence estimate, 69.2%; 95% CI, 45.9-92.5) following SCT. The 30-day overall mortality rates due to influenza-LRDs, respiratory syncytial virus-LRDs, HPIV-LRDs, and human rhinovirus-LRDs were 35.7, 25.8, 31.6, and 42.8%, respectively. Co-pathogens in respiratory specimens were detected in 23 (33.8%) patients. The overall mortality at day 30 after CRV-LRD diagnosis was 32.8% (22/67). High-dose steroid usage (p=0.025), a severe state of immunodeficiency (p=0.033), and lymphopenia (p=0.006) were significantly associated with death within 30 days following CRV-LRD diagnosis in a univariate analysis. Multivariate logistic regression analysis revealed that high-dose steroid usage [odds ratio (OR), 4.05; 95% CI, 1.12-14.61; p=0.033] and lymphopenia (OR, 6.57; 95% CI, 1.80-24.03; p=0.004) were independent risk factors for mortality within 30 days of CRV-LRDs.

CONCLUSION

CRV-LRDs among SCT recipients showed substantially high morbidity and mortality rates. Therefore, the implement of an active diagnostic approaches for CRV infections is required for SCT recipients with respiratory symptoms, especially those receiving high-dose steroids or with lymphopenia.

Viral Pneumonia in Patients with Hematologic Malignancy or Hematopoietic Stem Cell Transplantation

Viral pneumonias in patients with hematologic malignancies and recipients of hematopoietic stem cell transplantation cause significant morbidity and mortality. Advances in diagnostic techniques have enabled rapid identification of respiratory viral pathogens from upper and lower respiratory tract samples. Lymphopenia, myeloablative and T-cell depleting chemotherapy, graft-versus-host disease, and other factors increase the risk of developing life-threatening viral pneumonia. Chest imaging is often nonspecific but may aid in diagnoses. Bronchoscopy with bronchoalveolar lavage is recommended in those at high risk for viral pneumonia who have new infiltrates on chest imaging.

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.

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.

Response to Hepatitis A Vaccination in Immunocompromised Travelers

BACKGROUND

Hepatitis A vaccines are highly immunogenic in healthy patients, but there is uncertainty about their immunogenicity in immunocompromised patients.

METHODS

Our study included immunocompromised patients who received 1 or 2 hepatitis A vaccinations between January 2011 and June 2013. We assessed factors that influenced the serologic response to vaccination. We performed a literature review of previous studies on hepatitis A vaccination in immunocompromised patients.

RESULTS

Of 85 immunocompromised patients, 65 used immunosuppressive drugs, 13 had received stem cell transplants, and 7 were infected with human immunodeficiency virus. After vaccination, 65 of 85 (76.5%) developed antibodies. Tumor necrosis factor α blocker use was associated with better serologic responses than other immunosuppressive drugs. Female patients were more compliant than male patients with postvaccination antibody titer measurements. In 11 relevant studies, antibody responses after the first and second vaccination averaged 37% and 82%, respectively. Factors that negatively influenced serologic response rates were high doses of immunosuppressive drugs, fewer hepatitis A vaccinations, and a short interval between vaccination and antibody measurement.

CONCLUSIONS

Immunocompromised patients showed moderate to good serologic responses to hepatitis A vaccination, but may need more time to develop immunity. Tumor necrosis factor α blocker use was associated with better antibody responses than other drugs. Specifically, male patients should be motivated to return for antibody titer measurements.

Immune defects in the risk of infection and response to vaccination in monoclonal gammopathy of undetermined significance and multiple myeloma

The plasma cell proliferative disorders monoclonal gammopathy of undetermined significance (MGUS) and malignant multiple myeloma (MM) are characterized by an accumulation of transformed clonal plasma cells in the bone marrow and production of monoclonal immunoglobulin. They typically affect an older population, with median age of diagnosis of approximately 70 years. In both disorders, there is an increased risk of infection due to the immunosuppressive effects of disease and conjointly of therapy in MM, and response to vaccination to counter infection is compromised. The underlying factors in a weakened immune response in MGUS and MM are as yet not fully understood. A confounding factor is the onset of normal aging, which quantitatively and qualitatively hampers humoral immunity to affect response to infection and vaccination. In this review, we examine the status of immune alterations in MGUS and MM and set these against normal aging immune responses. We focus primarily on quantitative and functional aspects of B-cell immunity. Furthermore, we review the current knowledge relating to susceptibility to infectious disease in MGUS and MM, and how efficacy of conventional vaccination is affected by proliferative disease-related and therapy-related factors.

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.

Influenza vaccines in immunosuppressed adults with cancer

BACKGROUND

Immunosuppressed cancer patients are at increased risk of serious influenza-related complications. Guidelines, therefore, recommend influenza vaccination for these patients. However, data on vaccine effectiveness in this population is lacking, and the value of vaccination in this population remains unclear.

OBJECTIVES

To assess the effectiveness of influenza vaccine in immunosuppressed adults with malignancies. The primary review outcome is all-cause mortality, preferably at the end of the influenza season. Influenza-like illness (ILI, a clinical definition), confirmed influenza, pneumonia, any hospitalization and influenza-related mortality were defined as secondary outcomes.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and LILACS databases up to August 2013. We searched the following conference proceedings: ICAAC, ECCMID, IDSA (infectious disease conferences), ASH, ASBMT, EBMT (hematological), and ASCO (oncological) between the years 2006 to 2010. In addition, we scanned the references of all identified studies and pertinent reviews. We searched the websites of the manufacturers of influenza vaccine. Finally, we searched for ongoing or unpublished trials in clinical trial registry databases using the website.

SELECTION CRITERIA

Randomized controlled trials (RCTs), prospective and retrospective cohort studies and case-control studies were considered, comparing inactivated influenza vaccines versus placebo, no vaccination or a different vaccine, in adults (16 years and over) with cancer. We considered solid malignancies treated with chemotherapy, haematological cancer patients treated or not treated with chemotherapy, cancer patients post-autologous (up to six months after transplantation) or allogeneic (at any time) hematopoietic stem cell transplantation.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the risk of bias and extracted data from included studies adhering to Cochrane methodology. Meta-analysis could not be performed because of different outcome and denominator definitions in the included studies.

MAIN RESULTS

We identified four studies: one RCT and three observational studies, including 2124 participants. One study reported results in person-years while the other three reported per person. The studies were performed between 1993 and 2012 and included adults with haematological diseases (two studies), patients following bone marrow transplantation (one study) and solid malignancies (three studies). Only two observational studies reported all-cause mortality; one showing an adjusted hazard ratio (HR) of 0.88 (95% CI 0.77 to 0.99) for death with vaccination and the other reporting an odds ratio (OR) of 0.43 (95% CI 0.26 to 0.71). The RCT reported a statistically significant reduction in ILI with vaccination, while no difference was observed in one observational study. Confirmed influenza rates were lower with vaccination in the three observational studies, the difference reaching statistical significance in one. Pneumonia was observed significantly less frequently with vaccination in one observational study, but no difference was detected in another or in the RCT. The RCT showed a reduction in hospitalizations following vaccination, while an observational study found no difference. No life-threatening or persistent adverse effects from vaccination were reported. The strength of evidence is limited by the low number of included studies and by their low methodological quality (high risk of bias).

AUTHORS' CONCLUSIONS

Observational data suggests a lower mortality with influenza vaccination. Infection-related outcomes were lower or similar with influenza vaccination. The strength of evidence is limited by the small number of studies and by the fact that only one was a RCT. Influenza vaccination is safe and the evidence, although weak, is in favour of vaccinating adults with cancer receiving chemotherapy.

A randomized trial of one versus two doses of influenza vaccine after allogeneic transplantation

Influenza infection after allogeneic hematopoietic cell transplantation (allo-HCT) can result in severe complications. The effectiveness of the annual vaccine depends on age, immune competence, and the antigenic potential of the 3 strains included. We hypothesized that a second vaccine dose, the standard of care for vaccine-naïve children, might improve post hematopoietic cell transplantation (HCT) immune responses. Patients >60 days post-HCT were randomized to receive either 1 (n = 33) or 2 (n = 32) influenza vaccine doses separated by 1 month. The primary endpoint was whether 2 vaccinations induced superior immunity; however, we found no difference. Secondary endpoints were to identify variables associated with responses. Both hemagglutination inhibition (HI; P < .005) and ELISpot responses (P = .03) were greater for patients vaccinated ≥ 1 year posttransplantation. Umbilical cord blood (UCB) recipients showed less IFN-γ responses (P < .001). Interestingly, there was a positive correlation between the total number of CD19(+) cells before vaccination and seroconversion (P = .01) and an inverse correlation for IFN-γ responses (P = .05). Variables not associated with vaccine responses included prevaccine CD4(+) cell counts (total, naïve, or memory), steroid usage at vaccination, age, or conditioning intensity. Time from transplantation to vaccination and absolute CD19(+) cell counts were the strongest predictors of vaccine responses. Methods to improve influenza vaccine responses after allo-HCT are needed.

Cellular and humoral immunity elicited by influenza vaccines in pediatric hematopoietic-stem cell transplantation

Immunity induced by influenza vaccines following hematopoietic stem-cell transplantation (HSCT) is poorly understood. Here, 14 pediatric recipients (mean age: 6 years) received H1N1 (n=9) or H1N1/H3N2 (n=5) vaccines at a median of 5.7 months post-HSCT (HLA-identical related bone-marrow graft: 10/14). Fourteen clinically-matched non-vaccinated recipients were included as controls. Cellular response to vaccination was assessed by a T-cell proliferation assay. Humoral response was assessed by H1N1-specific antibody titration. IL2 and IFNγ responses to influenza were also evaluated by an intracellular cytokine accumulation method for some of the recipients. Higher proliferative responses to H1N1 (p=0.0001) and higher H1N1-specific antibody titers (p<0.02) were observed in vaccines opposed to non-vaccinated recipients. In some cases, proliferative responses to H1N1 developed while at the same time antibody titers did not reach protective (≥1:40) levels. Most recipients vaccinated with only the H1N1 strain had proliferative responses to both H1N1 and H3N2 (median stimulation index H1N1: 96, H3N2: 126 in responders). Finally, IL2 responses predominated over IFNγ responses (p<0.02) to influenza viruses in responders. In conclusion, H1N1 vaccination induced substantial cell-mediated immunity, and to a lesser extent, humoral immunity at early times post-HSCT. H1N1/H3N2 T-cell cross-reactivity and protective (IL2) rather than effector (IFNγ) cytokinic profiles were elicited.

Efficacy and safety of oral oseltamivir for influenza prophylaxis in transplant recipients

BACKGROUND

Haematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT) recipients are at high risk for severe influenza and its complications, and may not be adequately protected by vaccination.

METHODS

Liver, kidney, or liver-kidney transplant or allogeneic HSCT recipients aged ≥1 year were randomized to oseltamivir (75 mg once daily for those ≥13 years or weight-based dosing for children 1-12 years) or placebo for 12 weeks during periods of local influenza circulation. Patients were assessed for influenza infection via daily diary, every-other-week culture and PCR, and baseline and end-of-treatment serology.

RESULTS

A total of 477 subjects were enrolled (239 oseltamivir and 238 placebo); most were adults (96%) and SOT recipients (81%). In the intent-to-treat population, the frequency of laboratory-confirmed clinical influenza (culture positive and/or >4-fold increase in haemagglutinin antibody inhibition [primary end point]) was similar in the oseltamivir and placebo groups (2.1% [5/237] and 2.9% [7/238]). Incidence of laboratory-confirmed influenza was significantly reduced in the oseltamivir group versus placebo when determined by reverse transcriptase-PCR (1.7% [4/237] versus 8.4% [20/238]; 95% CI 2.8, 11.1) or viral culture (<1% [1/237] versus 3.8% [9/238]; 95% CI 0.7, 6.6), giving protective efficacies of 79.9 and 88.8%, respectively. Serious adverse events (oseltamivir 8% and placebo 10%) and adverse events (oseltamivir 55% and placebo 58%) were reported in both arms with a similar frequency. One illness due to oseltamivir-resistant A/H1N1 virus was detected in each group.

CONCLUSIONS

Oseltamivir prophylaxis is generally well-tolerated and may reduce culture- or PCR-confirmed influenza incidence in transplant recipients.

How Does Influenza A (H1N1) Infection Proceed in Allogeneic Stem Cell Transplantation Recipients?

The clinical course of influenza A (H1N1) infection in allogeneic hematopoietic stem cell transplantation (AHSCT)recipients is not clearly known. We report 3 AHSCT recipients that were infected with influenza A (H1N1). Each of thepatients had a different hematological disease and was at a different post-transplantation stages. All the patients weretreated with oseltamivir, and zanamivir was switched to oseltamivir in 1 patient. All the patients survived without anycomplications. The course of swine flu can vary and progress with bacterial or other viral infections in immunosuppressedpatients.

Clinical features and outcome of 2009-influenza A (H1N1) after allogeneic hematopoietic SCT

The impact of the 2009 H1N1-Influenza A (H1N1) pandemic in allogeneic hematopoietic SCT recipients (allo-HSCT) is not yet well defined. Between May 2009 and May 2010, all allo-HSCTs who presented with respiratory symptoms were screened for the presence of the H1N1 virus. Oseltamivir resistance was assessed and chart reviews were performed for all cases. In all, 51 of 248 (20%) allo-HSCT recipients followed at our outpatient clinic were screened. We identified 10 patients with H1N1 infection. Close contact with children was the most commonly suspected mode of transmission. Upper and lower respiratory tract infections were present in eight and five patients, respectively. Lymphopenia (<1 G/L) was the most frequent biological abnormality. High immunosuppression was responsible for severe infection requiring mechanical ventilation associated with prolonged viral shedding in three patients who had significant comorbidities and GvHD. Two of them developed an oseltamivir-resistant strain and both patients died subsequently despite intensive therapy, resulting in a case fatality rate of 20%. In conclusion, although most allo-HSCTs had mild symptoms from H1N1 infection, severe immunosuppression and emergence of oseltamivir resistance were likely responsible for a substantial morbidity, further supporting the need for vaccination and monitoring of close contacts, especially children.

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.

Influenza vaccination for immunocompromised patients: systematic review and meta-analysis from a public health policy perspective

BACKGROUND

Immunocompromised patients are vulnerable to severe or complicated influenza infection. Vaccination is widely recommended for this group. This systematic review and meta-analysis assesses influenza vaccination for immunocompromised patients in terms of preventing influenza-like illness and laboratory confirmed influenza, serological response and adverse events.

METHODOLOGY/PRINCIPAL FINDINGS

Electronic databases and grey literature were searched and records were screened against eligibility criteria. Data extraction and risk of bias assessments were performed in duplicate. Results were synthesised narratively and meta-analyses were conducted where feasible. Heterogeneity was assessed using I(2) and publication bias was assessed using Begg's funnel plot and Egger's regression test. Many of the 209 eligible studies included an unclear or high risk of bias. Meta-analyses showed a significant effect of preventing influenza-like illness (odds ratio [OR]=0.23; 95% confidence interval [CI]=0.16-0.34; p<0.001) and laboratory confirmed influenza infection (OR=0.15; 95% CI=0.03-0.63; p=0.01) through vaccinating immunocompromised patie nts compared to placebo or unvaccinated controls. We found no difference in the odds of influenza-like illness compared to vaccinated immunocompetent controls. The pooled odds of seroconversion were lower in vaccinated patients compared to immunocompetent controls for seasonal influenza A(H1N1), A(H3N2) and B. A similar trend was identified for seroprotection. Meta-analyses of seroconversion showed higher odds in vaccinated patients compared to placebo or unvaccinated controls, although this reached significance for influenza B only. Publication bias was not detected and narrative synthesis supported our findings. No consistent evidence of safety concerns was identified.

CONCLUSIONS/SIGNIFICANCE

Infection prevention and control strategies should recommend vaccinating immunocompromised patients. Potential for bias and confounding and the presence of heterogeneity mean the evidence reviewed is generally weak, although the directions of effects are consistent. Areas for further research are identified.