Risk factors and characteristics influencing humoral response to COVID-19 vaccination in patients after allogeneic stem cell transplantation.

Introduction: Vaccination against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is approved and recommended for immunocompromised patients such as patients after allogeneic stem cell transplantation (allo-SCT). Since infections represent a relevant cause of transplant related mortality we analyzed the advent of immunization to SARS-CoV-2 vaccination in a bicentric population of allogeneic transplanted patients. Methods: We retrospectively analyzed data of allo-SCT recipients in two German transplantation centers for safety and serologic response after two and three SARS-CoV-2 vaccinations. Patients received mRNA vaccines or vector-based vaccines. All patients were monitored for antibodies against SARS-CoV2-spike protein (anti-S-IgG) with an IgG ELISA assay or an EIA Assay after two and three doses of vaccination. Results: A total of 243 allo-SCT patients underwent SARS-CoV-2 vaccination. The median age was 59 years (range 22-81). While 85% of patients received two doses of mRNA vaccines, 10% had vector-based vaccines and 5% received a mixed vaccination. The two vaccine doses were well tolerated with only 3% patients developing a reactivation of graft versus host disease (GvHD). Overall, 72% of patients showed a humoral response after two vaccinations. In the multivariate analysis age at time of allo-SCT (p=0.0065), ongoing immunosuppressive therapy (p= 0.029) and lack of immune reconstitution (CD4-T-cell counts <200/µl, p< 0.001) were associated with no response. Sex, intensity of conditioning and the use of ATG showed no influence on seroconversion. Finally, 44 out of 69 patients that did not respond after the second dose received a booster and 57% (25/44) showed a seroconversion. Discussion: We showed in our bicentric allo-SCT patient cohort, that a humoral response could be achieve after the regular approved schedule, especially for those patients who underwent immune reconstitution and were free from immunosuppressive drugs. In over 50% of the initial non-responders after 2-dose vaccination, a seroconversion can be achieved by boostering with a third dose.

Pediatric allogeneic stem cell transplantation from adult SARS-COV-2 positive donor

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) is the cause of COVID-19. Almost 50% of infected people with the virus are asymptomatic. After the introduction of the COVID-19 vaccine, there is a significant reduction in symptomatic infection among vaccinated individuals. The possibility of viral transmission through blood products is unconfirmed yet. Case report: We report a successful hematopoietic stem cell transplant (HSCT) in a patient with sickle cell anemia from an asymptomatic COVID-19-positive donor who underwent stem cell collection under general anesthesia. No complications were encountered during and after the procedure. The marrow was infused safely with good immune reconstitution in the recipient. Conclusion(s): The report suggests that an asymptomatic COVID-19 positive person might be an acceptable HSCT donor possibly due to existing milder variants of COVID-19.Copyright © 2023 Pediatric Hematology Oncology Chapter of Indian Academy of Pediatrics

Treatment of blast phase chronic myeloid leukaemia: A rare and challenging entity.

Despite the success of BCR-ABL-specific tyrosine kinase inhibitors (TKIs) such as imatinib in chronic phase (CP) chronic myeloid leukaemia (CML), patients with blast phase (BP)-CML continue to have a dismal outcome with median survival of less than one year from diagnosis. Thus BP-CML remains a critical unmet clinical need in the management of CML. Our understanding of the biology of BP-CML continues to grow; genomic instability leads to acquisition of mutations which drive leukaemic progenitor cells to develop self-renewal properties, resulting in differentiation block and a poor-prognosis acute leukaemia which may be myeloid, lymphoid or bi-phenotypic. Similar advances in therapy are urgently needed to improve patient outcomes; however, this is challenging given the rarity and heterogeneity of BP-CML, leading to difficulty in designing and recruiting to prospective clinical trials. This review will explore the treatment of BP-CML, evaluating the data for TKI therapy alone, combinations with intensive chemotherapy, the role of allogeneic haemopoietic stem cell transplantation, the use of novel agents and clinical trials, as well as discussing the most appropriate methods for diagnosing BP and assessing response to therapy, and factors predicting outcome.

The impact of COVID-19 on acute myeloid leukemia patients undergoing allogeneic stem cell transplantation: a concise review.

This study aimed to delineate the possible impact of COVID-19 on acute myeloid leukemia (AML) patients in terms of diagnosis, chemotherapy, bone marrow transplant, and vaccination response. Allogeneic stem cell transplantation is markedly affected by the COVID-19 pandemic, as both donors and recipients must be healthy for transplantation to be feasible and successful. Delays in the identification of well-matched donors have been predicted, and represent a special challenge. Therefore, future donors should be tested for COVID-19. The outcome of delayed transplantation is vague and masked by variations in stem cell source along with disease subtype. However, if transplant delay results in recurrence of minimal residual disease, a negative impact on survival is anticipated.

Attenuated humoral response against SARS-CoV-2 mRNA vaccination in allogeneic stem cell transplantation recipients.

Antibody persistence several months after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccination in allogeneic stem cell transplantation recipients remains largely unknown. We sequentially evaluated the humoral response to two doses of mRNA vaccines in 128 adult recipients and identified the risk factors involved in a poor response. The median interval between stem cell transplantation and vaccination was 2.7 years. The SARS-CoV-2 S1 Ab became positive after the second vaccination dose in 87.6% of the recipients, and the median titer was 1235.4 arbitrary units (AU)/ml. In patients on corticosteroid treatment, the corticosteroid dose inversely correlated with Ab titer. Multivariate analysis identified risk factors for poor peak response such as an interval from stem cell transplantation ≤1 year, history of clinically significant CMV infection, and use of >5 mg/day prednisolone at vaccination. Six months after vaccination, the median titer decreased to 185.15 AU/ml, and use of >5 mg/day prednisolone at vaccination was significantly associated with a poor response. These results indicate that early vaccination after stem cell transplantation (<12 months) and CMV infection are risk factors for poor peak response, while steroid use is important for a peak as well as a persistent response. In conclusion, although humoral response is observed in many stem cell transplantation recipients after two doses of vaccination, Ab titers diminish with time, and factors associated with persistence and a peak immunity should be considered separately.

Pre-exposure prophylaxis with tixagevimab/cilgavimab (AZD7442) prevents severe SARS-CoV-2 infection in recipients of allogeneic hematopoietic stem cell transplantation during the Omicron wave: a multicentric retrospective study of SFGM-TC.

Since the emergence of the Omicron variant of SARS-CoV-2, though considered less virulent, hospitalization and death rates among immunocompromised patients remain high, especially for poor responders to vaccination. We conducted a retrospective multicentric study to evaluate pre-exposure prophylaxis with AZD7442 (tixagevimab/cilgavimab) for preventing COVID-19 in adult allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients. Among the 161 patients of our cohort, 22 (14%) contracted COVID-19 after a median follow-up of 105 days, but no severe form was observed. Only one major adverse event was reported: an acute coronary syndrome, resolved without sequelae. Pending randomized controlled trial results, our data support the use of AZD7442 as pre-exposure prophylaxis for COVID-19 during Omicron wave in allo-HSCT patients who failed to develop humoral immunity to vaccination, to prevent severe and potentially lethal forms of SARS-CoV-2 infection.

mRNA-1273 SARS-CoV-2 vaccine safety and COVID-19 risk perception in recently transplanted allogeneic hematopoietic stem cell transplant recipients.

PURPOSE: This study aims to describe the incidence and severity of adverse events (AEs) following the mRNA-1273 SARS-CoV-2 vaccine and explore the risk perception of COVID-19 in allogeneic hematopoietic stem cell transplant (HCT) recipients. METHODS: We performed a single-center prospective study including recently transplanted (< 2 years post-infusion) allogeneic HCT recipients. AEs were assessed through phone calls and graded from 0 to 4, while COVID-19 risk perception was measured using the Brief Illness Perception Questionnaire (BIP-Q5). RESULTS: Fifty-four HCT recipients were evaluated. Incidence and grades of AE (94.4% and 85.2% after the first and second dose, respectively) were similar to those described in the general population. The most common AE was pain at the site of injection. Three patients (5.6%) developed a grade ≥ 3 AE. Vaccine-related cytopenias and graft-versus-host disease flares were not observed. Female sex (OR 3.94, 95% CI 1.14-13.58, p = 0.03) and time since HCT (per month since HCT: OR 1.09, 95% CI 1.01-1.18, p = 0.04) were associated with the occurrence of any AE. The patients' risk perception level of COVID-19 decreased over time (p < 0.05). CONCLUSION: Our study confirms that the mRNA-1273 SARS-CoV-2 vaccine is safe in recent HCT recipients and suggests that the perceived risk of COVID-19 decreases over time.

EFFECT OF ANTI-SPIKE NEUTRALIZING MONOCLONAL ANTIBODIES ON COVID-19 PROGRESSION AND TIME TO VIRAL CLEARANCE IN PATIENTS WITH HEMATOLOGICAL MALIGNANCIES AND SARS-COV-2 INFECTION: THE GIMEMA EXPERIENCE

Background: Patients with hematological malignancies (HM) infected with SARS-CoV-2 hae a higher risk of deeloping seere coronairus disease (COVID-19) with consequent death, due to immune system impairment. Anti-spike Neutralizing Monoclonal Antibodies (nMoAbs) are indicated for the treatment of paucisymptomatic COVID-19 patients, but eidence of safety and efficacy among HM subjects is still lacking. Aims: To assess the efficacy of different nMoAbs approed by Agenzia Italiana del Farmaco (AIFA) on HM patients affected by paucisymptomatic SARS-COV-2. Methods: Multicenter retrospectie obserational study at ten sites in Italy, which enrolled consecutie patients with SARS-CoV-2 infection and treated with nMoAbs from February 2020 to December 2021. Only HM subjects on treatment or in disease remission within 6 months from treatment discontinuation with paucisymptomatic SARSCOV- 2 infection were included. nMoAbs approed by AIFA include Bamlaniimab, Bamlaniimab/Eteseimab, Casiriimab/Imdeimab, Sotroimab, and Regdanimab. The primary endpoint was to assess the time to SARS-CoV- 2 molecular swab negatiization. A comparison to an historical control not receiing nMoAbs was assessed. Secondary endpoints consisted in ealuation of Hospitalization rate due to COVID-19, including intensie care unit (ICU) admission rate due to respiratory failure, and safety assessment. Results: Oerall 51 HM patients (median age 62 years;35% women) were ealuated. Seenteen of them had non- Hodgkin lymphomas, 9 multiple myeloma, 6 chronic lymphocytic leukemia, 6 acute myeloid leukemia, 3 Hodgkin lymphoma, 2 acute lymphoblastic leukemia, 2 myeloproliferatie neoplasm, 1 Waldenstrom macroglobulinemia and 5 had other HM diagnosis. Thirty-six patients were on actie treatment, whereas 11 had completed their therapies within 6 months from nMoAbs administration, for 4 patients data were missing. In 7 subjects the last treatment was chemotherapy, in 19 immunotherapy with or without chemotherapy, in 9 target therapy, in 4 autologous stem cell transplantation, in 2 allogeneic stem cell transplantation, for 4 patients data were missing. Detailed description of patients' characteristics is reported in table 1. Twenty-six patients were treated with Bamlaniimab/Eteseimab, 17 with Casiriimab/Imdeimab, 3 with Bamlaniimab, and 2 with Sotroimab, for 3 patients data were missing. Median time to SARS-CoV-2 molecular swab negatiization was ealuable in 41 subjects and was 17 days (min 5, IQR 12-26, max 174). This result compared well with the preious finding of 28 days reported in an historical group of HM patients not treated with nMoAbs. We did not find any subpopulation, according to age, diagnosis, period of infection or type of nMoAbs who achieed a major benefit from nMoAbs treatment. The rate of Hospitalization due to COVID-19 progression was 19% (10/51), with an extremely low percentage of patients requiring ICU admission due to seer COVID-19 (2%,1/51). Most frequent side effects included chills (8%), diarrhea (6%), headache (2%), nausea (2%) and omiting (2%). Summary/Conclusion: Among paucisymptomatic SARS-CoV-2 positie HM patients on actie treatment or in disease remission within 6 months from treatment discontinuation, the administration of nMoAbs substantially reduced the time to swab negatiization compared to an historical control of HM subjects. This treatment was also able to reduce the rate of Hospitalization and death due to COVID-19 progression in this high risk group. (Table Presented).

Overall Survival Rate in Allogeneic Stem Cell Transplanted Patients Requiring Intensive Care Can Be Predicted by the Prognostic Index for Critically Ill Allogeneic Transplantation Patients (PICAT) and the Sequential Organ Failure Assessment (SOFA) Scores.

Background. Allogeneic hematopoietic stem cell transplantation (allo-HCT) recipients requiring intensive care unit (ICU) have high mortality rates. Methods. In the current study, we retrospectively assessed whether the Prognostic Index for Critically Ill Allogeneic Transplantation patients (PICAT) score predicted overall survival in a cohort of 111 consecutive allo-HCT recipients requiring ICU. Results. Survival rates at 30 days and 1 year after ICU admission were 57.7% and 31.5%, respectively, and were significantly associated with PICAT scores (p = 0.036). Specifically, survival at 30-day for low, intermediate, and high PICAT scores was 64.1%, 58.1%, and 31.3%, respectively. At one-year, the figures were 37.5%, 29%, and 12.5%, respectively. In multivariate analyses, high PICAT score (HR = 2.23, p = 0.008) and relapse prior to ICU admission (HR = 2.98, p = 0.0001) predicted higher mortality. We next compared the ability of the PICAT and the Sequential Organ Failure Assessment (SOFA) scores to predict mortality in our patients using c-statistics. C statistics for the PICAT and the SOFA scores were 0.5687 and 0.6777, respectively. Conclusions. This study shows that while the PICAT score is associated with early and late mortality in allo-HCT recipients requiring ICU, it is outperformed by the SOFA score to predict their risk of mortality.

Impact of cancer diagnosis, stage, and systemic therapies on immunogenicity after COVID-19 vaccination in patients with cancer: A systematic review and metaanalysis

Background: Patients (pts) with cancer are at increased risk of severe COVID-19. Both underlying malignancy and anti-cancer treatments influence the immune system, potentially impacting the level of vaccine protection achieved. Methods: A systematic literature search of PubMed, Embase, CENTRAL and conference proceedings (ASCO annual meetings and ESMO congress) up to 28/09/21, was conducted to identify studies reporting anti-SARS-CoV-2 spike protein immunoglobulin G seroconversion rates (SR) at any time point after complete COVID-19 immunization (mRNA- or adenoviral-based vaccines) in cancer pts. Complete immunization was defined as 1 dose of JNJ-78436735 vaccine or 2 doses of BNT162b2, mRNA-1273 or ChAdOx1 nCoV-19 vaccines. Subgroup analyses were performed to examine the impact of cancer diagnosis, disease stage, and anticancer therapies on the SR. Overall effects were pooled using random-effects models and reported as pooled SR with 95% confidence intervals (CI). Results: Of 1,548 identified records, 64 studies were included in this analysis reporting data from 10,511 subjects. The Table shows the SR in the overall population and specific subgroups. In pts with solid malignancies (SM), disease stage and primary site did not significantly impact the SR. In pts with hematologic malignancies (HM), SR were significantly lower in pts with chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL) compared to acute lymphoblastic leukemia (ALL), Hodgkin lymphoma (HL), and multiple myeloma (MM). Concerning the impact of cancer therapies on SR, pts with SM undergoing chemotherapy had numerically lower SR (N = 1,234, SR 87%, CI 81-92) compared to those treated with immune checkpoint inhibitors (N = 574, SR 94%, CI 88-97) or endocrine therapy (N = 326, SR 94%, CI 86-97) with or without another targeted therapy. Pts with HM treated with anti-CD20 therapy (within the last 12 months: N = 360, SR 7%, CI 2-20;or more than 12m: N = 175, SR 59%, CI 35-80), immune-modulating agents (BTK or BCL2 inhibitors) (N = 462, SR 47%, CI 32-64%) or other immunotherapies (anti-CD19/CART or anti-CD38) (N = 293, SR 37%, CI 23-53) had lower SR compared to pts treated with autologous (N = 353, SR 77%, CI 67- 85) or allogenic stem cell transplantation (N = 509, SR 77%, CI 68-84). Conclusions: SR varies between cancer types and anticancer therapies with some cancer pts having low protection against COVID- 19 even after complete vaccination.

SARS-CoV-2 vaccine response and rate of breakthrough infection in patients with hematological disorders.

BACKGROUND: The clinical efficacy of SARS-CoV-2 vaccines according to antibody response in immunosuppressed patients such as hematological patients has not yet been established. PATIENTS AND METHODS: A prospective multicenter registry-based cohort study conducted from December 2020 to December 2021 by the Spanish transplant and cell therapy group was used to analyze the relationship of antibody response at 3-6 weeks after full vaccination (2 doses) with breakthrough SARS-CoV-2 infection in 1394 patients with hematological disorders. RESULTS: At a median follow-up of 165 days after complete immunization, 37 out of 1394 (2.6%) developed breakthrough SARS-CoV-2 infection at median of 77 days (range 7-195) after full vaccination. The incidence rate was 6.39 per 100 persons-year. Most patients were asymptomatic (19/37, 51.4%), whereas only 19% developed pneumonia. The mortality rate was 8%. Lack of detectable antibodies at 3-6 weeks after full vaccination was the only variable associated with breakthrough infection in multivariate logistic regression analysis (Odds Ratio 2.35, 95% confidence interval 1.2-4.6, p = 0.012). Median antibody titers were lower in cases than in non-cases [1.83 binding antibody units (BAU)/mL (range 0-4854.93) vs 730.81 BAU/mL (range 0-56,800), respectively (p = 0.007)]. We identified 250 BAU/mL as a cutoff above which incidence and severity of the infection were significantly lower. CONCLUSIONS: Our study highlights the benefit of developing an antibody response in these highly immunosuppressed patients. Level of antibody titers at 3 to 6 weeks after 2-dose vaccination links with protection against both breakthrough infection and severe disease for non-Omicron SARS-CoV-2 variants.

Impact of Cryopreservation of Peripheral Blood Stem Cells (PBSC) in Transplantation from Matched Unrelated Donor (MUD).

Background: Cryopreservation of PBSC for allogenic hematopoietic stem cell transplantation (allo-HSCT) was implemented due to the current Coronavirus 2019 pandemic. The impact of match unrelated donor (MUD) graft freezing on the outcome of allo-HSCT in terms of hematological recovery, graft versus host disease (GVHD), and survival are still controversial. Methods: In this study, we compared graft composition, clinical characteristics, and outcome of 31 allo-HSCT from MUD cryopreserved PBSC (Cryo Group) with 23 matched-pair allo-HSCT from fresh MUD PBSC (Fresh Group) performed in our center between January 2020 and July 2021. Results: No significant differences were recognized in clinical characteristics of patients, donors, and transplants between the Cryo and Fresh groups except for a better prognostic comorbidity index (HCT-CI) of the Cryo group. In the Cryo Group, the median time from apheresis to cryopreservation was 46.0 h (range 23.8-53.5), while the median time from cells collection and reinfusion was 13.9 days (range 5.8-28.1). In the Fresh Group, median time from apheresis to reinfusion was 35.6 h (range 21.4-51.2). The number of viable (7-AAD negative) CD34+ cells per kg patient infused was significantly lower in the Cryo Group (5.2 ± 1.9 × 106/kg vs. 7.0 ± 1.3 × 106/kg; p < 0.001). Indeed, there was a 36% (11-70) median loss of viable CD34+/kg cells after freezing. All patients engrafted: median time to neutrophil engraftment (>0.5 × 109/L) was 13.5 days (range 12-15) for Cryo Group and 14 days (range 13-16) days for Fresh Group (p = 0.522), while the median time to platelet engraftment (>20 × 109/L) was, respectively, 14 (range 12-18) and 15 (range 12-17) days (p = 0.904). The incidence of grade ≥ 2 acute GVHD was similar in the two groups (56.5% Cryo Group vs. 60.0% Fresh Group; p = 0.832) and no differences in terms of OS (p = 0.090), PFS (p = 0.200) and TRM (p = 0.970) were observed between the Cryo and Fresh groups. Conclusions: In our series, no differences between the Cryo and Fresh groups were found in engraftment, grade ≥ 2 acute GVHD incidence, OS, PFS, and TRM despite a lower CD34+ infused dose in the Cryo Group. Frozen PBSCs could be considered a safe option also for allo-HSCT from MUD but a higher amount of PBSC should be collected to warrant an adequate viable CD34+ post-thawing.

Applicability of probabilistic graphical models for early detection of SARS-CoV-2 reactive antibodies after SARS-CoV-2 vaccination in hematological patients.

Prior studies of antibody response after full SARS-CoV-2 vaccination in hematological patients have confirmed lower antibody levels compared to the general population. Serological response in hematological patients varies widely according to the disease type and its status, and the treatment given and its timing with respect to vaccination. Through probabilistic machine learning graphical models, we estimated the conditional probabilities of having detectable anti-SARS-CoV-2 antibodies at 3-6 weeks after SARS-CoV-2 vaccination in a large cohort of patients with several hematological diseases (n= 1166). Most patients received mRNA-based vaccines (97%), mainly Moderna® mRNA-1273 (74%) followed by Pfizer-BioNTech® BNT162b2 (23%). The overall antibody detection rate at 3 to 6 weeks after full vaccination for the entire cohort was 79%. Variables such as type of disease, timing of anti-CD20 monoclonal antibody therapy, age, corticosteroids therapy, vaccine type, disease status, or prior infection with SARS-CoV-2 are among the most relevant conditions influencing SARS-CoV-2-IgG-reactive antibody detection. A lower probability of having detectable antibodies was observed in patients with B-cell non-Hodgkin's lymphoma treated with anti-CD20 monoclonal antibodies within 6 months before vaccination (29.32%), whereas the highest probability was observed in younger patients with chronic myeloproliferative neoplasms (99.53%). The Moderna® mRNA-1273 compound provided higher probabilities of antibody detection in all scenarios. This study depicts conditional probabilities of having detectable antibodies in the whole cohort and in specific scenarios such as B cell NHL, CLL, MM, and cMPN that may impact humoral responses. These results could be useful to focus on additional preventive and/or monitoring interventions in these highly immunosuppressed hematological patients.

CD147 expression and polymorphism as markers of cytomegalovirus infection in acute myeloid leukemia patients following allogeneic stem cell transplantation

CD147 (BSG, EMMPRIN) is a multifunctional immunoglobulin involved in pathogenesis of many diseases. It was shown to facilitate various viral infections, such as measles virus and SARS-CoV-2, and was reported to have a role in cytomegalovirus (CMV) infection. While mostly working as a membrane-bound protein, it can be released by cells in a soluble form that can be detected in serum. Our recent studies showed that CD147 polymorphism and serum level may be associated with risk and survival in acute myeloid leukemia (AML) patients. This prompted us to investigate CD147 serum levels and genotypes in AML patients with CMV infection after allogeneic stem cell transplantation (SCT). CD147 was measured using Quantikine ELISA Human EMMPRIN/ CD147 Immunoassay in serum of 16 AML patients undergoing SCT, of whom nine developed CMV infection, and 25 controls. Genotyping of CD147 variants was performed on 170 DNA samples, including 135 healthy individuals and 35 patients (18 with CMV infection) using Taqman assays. Serum CD147 levels were higher in patients with CMV infection than in those without detectable CMV infection (p = 0.026) and controls (p < 0.001). CD147 allele rs4919859C, a marker of risk and worse survival in AML, tended to be more common in patients with CMV infection than those without infection (p = 0.094). Furthermore, we built a logistic regression model incorporating the type of conditioning, sex of transplant donor and recipient, type of donor (related/ unrelated), donor and recipient serologic CMV status, and presence/absence of the rs4919859 C allele. The analysis confirmed allele rs4919859 C (p = 0.044) and recipient CMV status (p = 0.035) as independent markers of CMV infection. Our results suggest that higher serum CD147 levels and presence of the CD147 rs4919859C allele may be markers of CMV infection in AML patients undergoing SCT.

High Mortality of COVID-19 Early after Allogeneic Stem Cell Transplantation: A Retrospective Multicenter Analysis on Behalf of the German Cooperative Transplant Study Group.

Recipients of allogeneic stem cell transplantation (alloSCT) are at high risk for contracting infectious diseases with high morbidity and mortality. Coronavirus disease 2019 (COVID-19) is a viral respiratory disease that can lead to severe pneumonia and acute respiratory distress syndrome, with a potentially fatal outcome. In this retrospective study conducted on behalf of the German Cooperative Transplant Study Group, we aimed to analyze risk factors, disease course, and outcomes of COVID-19 in patients who underwent alloSCT. AlloSCT recipients who became infected with SARS-CoV-2 at German and Austrian transplant centers between February 2020 and July 2021 were included. Classification of COVID-19 severity into mild, moderate-severe, or critical disease and division of the course of the pandemic into 4 phases were done according to the German Robert Koch Institute. The main endpoint was overall mortality at the end of follow-up. We further analyzed the need for treatment in an intensive care unit (ICU) and the severity of disease. Risk factors were evaluated using univariate and multivariate analyses, and survival analysis was performed using Kaplan-Meier method. The study cohort comprised 130 patients from 14 transplant centers, with a median age at diagnosis of COVID-19 of 59 years (range, 20 to 81 years) and a median interval between alloSCT and COVID-19 of 787 days (range, 19 to 8138 days). The most common underlying diseases were acute myeloid leukemia (45.4%) and lymphoma (10.8%). The majority of patients (84.9%) were infected in the later phases of the pandemic; 20.8% had moderate-severe disease, 12.3% had critical disease, and 19.2% were treated in an ICU. After a median follow-up of 127 days, overall mortality was 16.2%, 52.0% among patients treated in an ICU. Risk factors for mortality in multivariate analysis were active disease (odds ratio [OR], 4.46), infection with SARS-CoV-2 ≤365 days after alloSCT (OR, 5.60), age >60 years (OR, 5.39), and ongoing immunosuppression with cyclosporine (OR, 8.55). Risk factors for developing moderate-severe or critical disease were concurrent immunosuppression (OR, 4.06) and age >40 years (OR, 4.08). Patients after alloSCT exhibit a substantially increased mortality risk after COVID-19 infection compared with the normal population, without considerable improvement over the course of the pandemic. Risk factors include age, early infection post-alloSCT, and active immunosuppression. Further studies are needed to improve prevention and treatment in this high-risk patient group.

Humoral Responses and Chronic GVHD Exacerbation after COVID-19 Vaccination Post Allogeneic Stem Cell Transplantation.

The COVID-19 pandemic threatens patients with a compromised immune and endothelial system, including patients who underwent allogeneic stem cell transplantation (alloSCT). Thus, there is an unmet need for optimizing vaccination management in this high-risk cohort. Here, we monitored antibodies against SARS-CoV-2 spike protein (anti-S1) in 167 vaccinated alloSCT patients. Humoral immune responses were detectable in 81% of patients after two vaccinations with either mRNA-, vector-based, or heterologous regimens. Age, B-cell counts, time interval from vaccination, and the type of vaccine determined antibody titres in patients without systemic immunosuppression (sIS). Similar to a healthy control cohort, mRNA vaccine-based regimens induced higher titres than vector-based vaccines. Patients on two or more immunosuppressants rarely developed immunity. In contrast, 62% and 45% of patients without or on only one immunosuppressant, respectively, showed a strong humoral vaccination response (titre > 100). Exacerbation of cGVHD upon vaccination was observed in 6% of all patients and in 22% of patients receiving immunosuppression for cGVHD. cGVHD exacerbation and low antibody titres were both associated with higher angiopoietin-2 (ANG2) serum levels. In conclusion, mRNA-based vaccines elicit strong humoral responses in alloSCT patients in the absence of double sIS. Biomarkers such as ANG2 might help with weighing cGVHD risk versus beneficial responses.

Antibody-response to mRNA SARS-CoV2 vaccination in patients after allogeneic stem cell transplantation

Introduction: Patients after allogeneic stem cell transplantation are at high risk for infection-related complications and vaccination efficacy might be impaired depending on the immune reconstitution. In this study we evaluate the response of 182 patients to mRNA vaccines against SARS-CoV2. Methods: During routine follow up visits, patients were asked about their vaccination status and if they had a previous infection with SARS-CoV2. In fully vaccinated patients, the antibody titer was measured using the Roche Elecsys Anti-SARS-CoV2 S test. A titer of <1 U/l was considered as negative, titers of >250 U/ml as a high antibody titer and a titer of 50-249 U/ml as a low antibody titer. Patient characteristics were evaluated by chart review to identify risk factors for poor vaccination response. Results: The majority of patients developed a high antibody titer (138 out 182 patients, 75.8%). Risk factors for a low antibody titer were im-munosuppressive therapy, a lymphocyte count <0.9 G/l, ongoing treatment for the underlying malignancy and active GvHD. The vaccine (Moderna vs Pfizer), donor type, underlying disease, a previous SARS-CoV2 infection and sex did not significantly influence the response to the vaccination. Discussion: While patients undergoing allogeneic stem cell transplantation have been excluded from the initial registration trials, our large patient cohort confirms the data of previous smaller studies, showing that most patients do have a good response to mRNA vaccines against SARS-CoV2. Nevertheless, a significant proportion of patients shows an inadequate vaccination response and thus qualifies for a third vaccination.