Serum IgM levels independently predict immune response to influenza vaccine in long-term survivors vaccinated at >1 year after undergoing allogeneic hematopoietic stem cell transplantation

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.

Emerging viral infections in immunocompromised patients: A great challenge to better define the role of immune response

The immune response to invading pathogens is characterized by the rapid establishment of a complex network of cellular interactions and soluble signals. The correct balancing of activating and regulating pathways and tissue-homing signals determines its effectiveness and persistence over time. Emerging viral pathogens have always represented a great challenge to the immune system and an often uncontrolled/imbalanced immune response has been described (e.g. cytokine storm, immune paralysis), contributing to the severity of the disease. Several immune biomarkers and cell subsets have been identified as major players in the cascade of events leading to severe diseases, highlighting the rationale for host-directed intervention strategy. There are millions of immunocompromised pediatric and adult patients worldwide (e.g. transplant recipients, hematologic patients, subjects with primary immune-deficiencies), experiencing an impaired immune reactivity, due to diseases and/or to the medical treatments. The reduced immune reactivity could have two paradoxical non-exclusive effects: a weak protective immunity on one hand, and a reduced contribution to immune-mediated pathogenetic processes on the other hand. In these sensitive contexts, the impact of emerging infections represents a still open issue to be explored with several challenges for immunologists, virologists, physicians and epidemiologists. In this review, we will address emerging infections in immunocompromised hosts, to summarize the available data concerning the immune response profile, its influence on the clinical presentation, the possible contribution of persistent viral shedding in generating new viral variants with improved immune escape features, and the key role of vaccination.

Immunogenicity profile after COVID-19 vaccination in patients with onco-hematological diseases

OBJECTIVE

To evaluate the influence of onco-hematological pathologies on seroconversion to COVID-19 vaccines, in addition to the effects of chemotherapy treatment on this response.

METHODS

The present study evaluated the immunogenic response of 76 patients with onco-hematological diseases to multiple vaccine platforms compared to 25 control individuals.

RESULTS

Our results showed positive response rates of 74.02% in patients with onco-hematological diseases and 100% in controls. When analyzed according to etiological group, patients with lymphoproliferative disorders achieved a positive vaccine response rate of 58.7%, whereas those with myeloproliferative diseases achieved a 100% response rate. We also observed that patients previously exposed to COVID-19 presented a 75% increase in their antibody values after vaccination, and these values were 37% higher than those of patients who did not have such exposure. We found that patients who underwent B-lymphocyte-depleting therapy in the last 2 years before vaccination had a worse response rate of 18.75%.

CONCLUSION

Despite the immunosuppression of patients with onco-hematological diseases, caused by the biology of their diseases and treatment, benefit and safety in vaccinating these patients are observed, in view of the important recall immune response and incidence of adverse effects similar to those of the healthy population.

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.

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.

An Immune Recovery-Based Revaccination Protocol for Pediatric Hematopoietic Stem Cell Transplant Recipients: Revaccination Outcomes Following Pediatric HSCT

Following hematopoietic stem cell transplant (HSCT), patients are at increased risk of vaccine-preventable diseases (VPDs) and experience worse outcomes of VPDs compared to immunocompetent patients. Therefore, patients are routinely vaccinated post-HSCT to restore VPD immunity. Published guidelines recommend revaccination based on time post-HSCT, although optimal revaccination timing and the value of using other clinical and laboratory variables to guide revaccination remain unclear. An institutional immune recovery-based protocol to guide timing of revaccination is used at Children's Hospital Colorado. This protocol incorporates time from transplant, time off immunosuppressive therapy and intravenous immunoglobulin replacement, absence of active graft-versus-host disease (GVHD), and minimum absolute CD4 count, absolute lymphocyte count (ALC), and immunoglobulin G (IgG) levels. The objective of this study is to evaluate the performance of this immune recovery-based revaccination protocol by determining rates of seroprotective vaccine responses achieved and describing demographic, clinical, and laboratory markers associated with protective antibody titers post-revaccination. Rates of seroprotection following revaccination were retrospectively determined for patients who received autologous or allogeneic HSCTs at Children's Hospital Colorado from 2007 to 2017. Percent seropositivity after revaccination was determined for ten VPDs: measles, mumps, rubella, varicella, tetanus, diphtheria, Haemophilus influenzae type B (Hib), poliovirus, hepatitis B virus (HBV), and Streptococcus pneumoniae. The impact of covariates, including post-HSCT vaccine timing, patient demographics, clinical features (diagnosis, donor and conditioning regimen data, GVHD, cytomegalovirus disease), and laboratory parameters (CD4 count, ALC, IgG level), on rates of seroprotection post-revaccination was determined using Wilcoxon rank sum, Fisher's exact, or chi-square tests, as appropriate. One hundred-twelve unique patients among 427 HSCT recipients had available data for both revaccination timing and vaccine titers. Among these, high rates of seroprotection were achieved after revaccination for rubella (100%), diphtheria (100%), tetanus (100%), and Hib (98%). More modest rates of seroprotection were achieved after revaccination with HBV (87%) and pneumococcal conjugate (85%) vaccines. Seroprotection was lower after revaccination with measles (76%), pneumococcal polysaccharide (72%), mumps (67%), and varicella (25%) vaccines. Greater rates of seroprotection were associated with younger age (hepatitis B vaccine, P = .04), lack of prior rituximab treatment (pneumococcal conjugate vaccine, P = .005), lack of total body irradiation (pneumococcal conjugate vaccine, P = .03), and receipt of a non-cord blood transplant (pneumococcal polysaccharide vaccine, P = .04). These results suggest that a revaccination protocol that incorporates both time post-HSCT and patient-specific indicators of immunologic recovery can achieve high rates of seroprotection against most VPDs. Seroprotection rates for HBV and PCV were notably among the highest reported in children post-HSCT, suggesting that an immune recovery-based protocol may improve seroprotection for some VPDs that frequently are associated with lower vaccine responses post-HSCT. Seroprotection rates for other VPDs remained suboptimal after revaccination. Therefore, evaluation of additional strategies, such as the use of novel markers of immune competence and new vaccines, to further optimize protection against VPDs in this population is warranted.

Influenza vaccination in immunocompromised populations: Strategies to improve immunogenicity

Immunocompromised individuals are at high risk of severe illness and complications from influenza infection. For this reason, immunization using inactivated influenza vaccines is recommended for transplant patients, individuals receiving immunosuppressant treatments, and other persons with immunodeficiency. However, these immunocompromised populations are more likely to have lower and non-protective responses to annual vaccination with a standard influenza vaccine. Here, we review strategies aimed to improve the immunogenicity of influenza vaccines in immunocompromised populations. The different strategies employed have included adjuvanted vaccines, high-dose vaccines, booster doses, intradermal vaccination, and temporary discontinuation of immunosuppressant treatment regimens. High-dose trivalent, inactivated, split-virus influenza vaccine (IIV3-HD) is so far one of the leading strategies for improving vaccine responses in HIV patients, transplant patients, and persons receiving immunosuppressant therapies for inflammatory diseases. Several studies in these populations have shown stronger humoral responses with IIV3-HD than existing standard-dose trivalent vaccine, and comparable safety. Accordingly, some scientific societies have stated that high-dose influenza vaccine could be a preferred option for immunocompromised patients. However, larger randomized controlled studies are needed to validate relative immunogenicity and safety of IIV3-HD and other enhanced vaccines and vaccination strategies in immunocompromised individuals.

Reducing infectious complications after allogeneic stem cell transplant

INTRODUCTION

Infections remain a significant problem, in patients undergoing an allogeneic hematopoietic stem-cell transplant (HSCT) and efforts have been made over the years, to reduce the incidence, morbidity and mortality of infectious complications.

AREAS COVERED

This manuscript is focused on the epidemiology, risk factors and prevention of infections after allogeneic HSCT. A systematic literature review was performed using the PubMed database, between November 2019 and January 2020, with the following MeSH terms: stem-cell transplantation, infection, fungal, bacterial, viral, prophylaxis, vaccines, prevention. The authors reviewed all the publications, and following a common revision, a summary report was made and results were divided in three sections: bacterial, fungal and viral infections.

EXPERT OPINION

Different infections occur in the early, intermediate and late post-transplant period, due to distinct risk factors. Improved diagnostic techniques, pre-emtive therapy and better prophylaxis of immunologic complications, have reduced the morbidity and mortality of infections. The role of the gut microbiota is under careful scrutiny and may further help us to identify high-risk patients.

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.

Seasonal influenza vaccine in immunocompromised persons

Immunocompromised persons are at high risk of complications from influenza infection. This population includes those with solid organ transplants, hematopoietic stem cell transplants, solid cancers and hematologic malignancy as well as those with autoimmune conditions receiving biologic therapies. In this review, we discuss the impact of influenza infection and evidence for vaccine effectiveness and immunogenicity. Overall, lower respiratory disease from influenza is common; however, vaccine immunogenicity is low. Despite this, in some populations, influenza vaccine has demonstrated effectiveness in reducing severe disease. Various strategies to improve influenza vaccine immunogenicity have been attempted including two vaccine doses in the same influenza season, intradermal, adjuvanted, and high-dose vaccines. The timing of influenza vaccine is also important to achieve optimal immunogenicity. Given the suboptimal immunogenicity, family members and healthcare professionals involved in the care of these populations should be vaccinated. Health care professional recommendation for vaccination is an important factor in vaccine coverage.