Predictors of Covid-19 Vaccination Response After In-Vivo T-Cell–Depleted Stem Cell Transplantation

Immunogenicity of mRNA-1273 and BNT162b2 in Immunocompromised Patients: Systematic Review and Meta-analysis Using GRADE

INTRODUCTION

Immunocompromised (IC) patients mount poor immune responses to vaccination. Higher-dose coronavirus disease 2019 (COVID-19) vaccines may offer increased immunogenicity.

METHODS

A pairwise meta-analysis of 98 studies reporting comparisons of mRNA-1273 (50 or 100 mcg/dose) and BNT162b2 (30 mcg/dose) in IC adults was performed. Outcomes were seroconversion, total and neutralizing antibody titers, and cellular immune responses.

RESULTS

mRNA-1273 was associated with a significantly higher seroconversion likelihood [relative risk, 1.11 (95% CI, 1.08, 1.14); P < 0.0001; I2 = 66.8%] and higher total antibody titers [relative increase, 50.45% (95% CI, 34.63%, 66.28%); P < 0.0001; I2 = 89.5%] versus BNT162b2. mRNA-1273 elicited higher but statistically nonsignificant relative increases in neutralizing antibody titers and cellular immune responses versus BNT162b2.

CONCLUSION

Higher-dose mRNA-1273 had increased immunogenicity versus BNT162b2 in IC patients.

Vaccine schedule recommendations and updates for patients with hematologic malignancy post-hematopoietic cell transplant or CAR T-cell therapy

Revaccination after receipt of a hematopoietic cell transplant (HCT) or cellular therapies is a pillar of patient supportive care, with the potential to reduce morbidity and mortality linked to vaccine-preventable infections. This review synthesizes national, international, and expert consensus vaccination schedules post-HCT and presents evidence regarding the efficacy of newer vaccine formulations for pneumococcus, recombinant zoster vaccine, and coronavirus disease 2019 in patients with hematological malignancy. Revaccination post-cellular therapies are less well defined. This review highlights important considerations around poor vaccine response, seroprevalence preservation after cellular therapies, and the optimal timing of revaccination. Future research should assess the immunogenicity and real-world effectiveness of new vaccine formulations and/or vaccine schedules in patients post-HCT and cellular therapy, including analysis of vaccine response that relates to the target of cellular therapies.

COVID-19 in hematopoietic stem-cell transplant recipients: A systematic review and meta-analysis of clinical characteristics and outcomes

Patients who undergo hematopoietic stem-cell transplantation (HSCT) are more susceptible to developing severe forms of COVID-19 with an increased risk of mortality. The aim of this study was to analyze, by performing a systematic review and meta-analysis, all studies that evaluated COVID-19 in HSCT adult recipients and present clinical characteristics and outcomes. Studies were eligible for inclusion if they: (I) described the clinical characteristics of COVID-19 in adult (aged 18 years old or above) HSCT recipients; (II) described outcomes of COVID-19 in this population, mainly lethality; (III) were full-text articles. We searched MedLine, Embase, SCOPUS, LILACS and Web of Science for full-text studies that evaluated COVID-19 in adult HSCT patients until 26 Apr 2023. Two independent reviewers screened the articles and extracted the data. The Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Studies Reporting Prevalence Data was used to assess quality of the included studies. Meta-analysis was performed and the pooled prevalence of severe/critical disease and of death with a 95% CI was calculated with the random-effects model. Sixteen studies were included; seven (43.7%) were multicenter. Most of the studies were from Europe (37.5%). All of them had a low risk of bias using the JBI Checklist. A total of 1186 patients were included. Allogeneic HSCT patients were the majority in most studies, with a total of 861 patients (72.5%). The symptomatic rate was 79.4%. The pooled prevalence of severe/critical COVID-19 was 24.0% (95% CI 0.13-0.36; I2  = 94%; n = 334/990). The pooled prevalence of death for the entire population was 17% (95% CI 0.13-0.22; I2  = 76%; n = 221/1117), 17% (95% CI 0.12-0.23; I2  = 67%; n = 152/822) for allogeneic-HSCT and 14% (95% CI 0.08-0.22; I4  = 65%; n = 48/293) for autologous-HSCT. In conclusion, frequently the infection of SARS-CoV-2 in HSCT was symptomatic and lethality is higher than in general population. Thus, it is essential to focus on the implementation of measures to mitigate the risk of SARS-CoV-2 infection in this population, as well as to carefully assess HSCT recipients who develop COVID-19.

Immunogenicity and Safety of Booster SARS-CoV-2 mRNA Vaccine Dose in Allogeneic Hematopoietic Stem Cell Transplantation Recipients

Allogeneic hematopoietic stem cell transplantation (HSCT) recipients are susceptible to severe outcomes of Coronavirus disease 2019 (COVID-19). Most guidelines recommend a fourth dose (ie, booster) of COVID-19 vaccine to reduce the infection risk, and observational studies are needed to determine the immunogenicity and safety of the booster dose in this population. The primary outcome was to determine the quantitative anti-receptor-binding domain (RBD) antibody titers after the fourth dose of the COVID-19 vaccine. The secondary outcomes included adverse effects and all-cause mortality. This single-group prospective cohort included allogeneic HSCT recipients age ≥18 years who received their fourth dose of COVID-19 mRNA vaccine between December 15, 2021, and August 2, 2022. We excluded patients with a history of COVID-19 diagnosis and those who received i.v. Ig within 21 days of antibody testing or rituximab within 6 months before study entry. We used regression models to determine the contributing factors significantly associated with post-fourth dose anti-RBD titer. Sixty-seven patients (median age, 59.5 years; IQR, 53.5 to 65.5 years; 33 males [61%]) received the fourth dose of vaccine, and 54 were included in the anti-RBD titer analysis. The median anti-RBD titers at 4 to 6 weeks after the third and fourth doses differed significantly (13,350 U/mL [IQR, 2618 to 34,740 U/mL] and 44,500 U/mL [IQR, 11,163 to 84,330 U/mL], respectively; P < .0001). In univariate analysis, the post-third dose anti-RBD titer (β = .70; 95% CI, .54 to .87; P < .001) and treatment with mycophenolate compounds (β = -1.05; 95% CI, -1.97 to -1.12; P = .03) significantly predicted the antibody response to the fourth dose. In multivariate analysis, the inverse association between treatment with mycophenolate compounds and the post-fourth dose anti-RBD antibody titer was not significant (β = -.57; 95% CI, -1.32 to .19; P = .14), whereas the significant association between the anti-RBD titers following the third and fourth doses did not change considerably (β = .66; 95% CI, .47 to .86; P < .001). The most frequent adverse event was vaccination site soreness (44%), followed by fatigue (16%), myalgia (4%), and headache (2%). No recipient experienced new or worsened preexisting graft-versus-host disease within 40 days of vaccination, and no patient died. Six patients (11%) developed breakthrough severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection not associated with hospitalization or severe outcomes. The fourth dose of the COVID-19 vaccine appears to be highly immunogenic and safe in allogeneic HSCT recipients. Further studies are needed to determine the neutralizing antibody titers against SARS-CoV-2 subvariants and the effectiveness and immunogenicity of bivalent vaccines in allogeneic HSCT recipients.

Stimulation of Potent Humoral and Cellular Immunity via Synthetic Dual-Antigen MVA-Based COVID-19 Vaccine COH04S1 in Cancer Patients Post Hematopoietic Cell Transplantation and Cellular Therapy

Hematopoietic cell transplantation (HCT) and chimeric antigen receptor (CAR)-T cell patients are immunocompromised, remain at high risk following SARS-CoV-2 infection, and are less likely than immunocompetent individuals to respond to vaccination. As part of the safety lead-in portion of a phase 2 clinical trial in patients post HCT/CAR-T for hematological malignancies (HM), we tested the immunogenicity of the synthetic modified vaccinia Ankara-based COVID-19 vaccine COH04S1 co-expressing spike (S) and nucleocapsid (N) antigens. Thirteen patients were vaccinated 3-12 months post HCT/CAR-T with two to four doses of COH04S1. SARS-CoV-2 antigen-specific humoral and cellular immune responses, including neutralizing antibodies to ancestral virus and variants of concern (VOC), were measured up to six months post vaccination and compared to immune responses in historical cohorts of naïve healthy volunteers (HV) vaccinated with COH04S1 and naïve healthcare workers (HCW) vaccinated with the FDA-approved mRNA vaccine Comirnaty® (Pfizer, New York, NY, USA). After one or two COH04S1 vaccine doses, HCT/CAR-T recipients showed a significant increase in S- and N-specific binding antibody titers and neutralizing antibodies with potent activity against SARS-CoV-2 ancestral virus and VOC, including the highly immune evasive Omicron XBB.1.5 variant. Furthermore, vaccination with COH04S1 resulted in a significant increase in S- and N-specific T cells, predominantly CD4+ T lymphocytes. Elevated S- and N-specific immune responses continued to persist at six months post vaccination. Furthermore, both humoral and cellular immune responses in COH04S1-vaccinated HCT/CAR-T patients were superior or comparable to those measured in COH04S1-vaccinated HV or Comirnaty®-vaccinated HCW. These results demonstrate robust stimulation of SARS-CoV-2 S- and N-specific immune responses including cross-reactive neutralizing antibodies by COH04S1 in HM patients post HCT/CAR-T, supporting further testing of COH04S1 in immunocompromised populations.

SARS-CoV-2 Vaccine-Induced Immune Responses Among Hematopoietic Stem Cell Transplant Recipients

Background

Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination reduces the risk and severity of coronavirus disease 2019 (COVID-19), several variables may impact the humoral response among patients undergoing hematopoietic stem cell transplantation (HSCT).

Methods

A retrospective chart review was conducted among SARS-CoV-2-vaccinated HSCT recipients between 2020 and 2022 at a single center in Boston, Massachusetts. Patients age ≥18 years who received doses of Pfizer, Moderna, or J&J vaccines were included. Anti-spike (S) immunoglobulin G (IgG) titer levels were measured using the Roche assay. Responders (≥0.8 U/mL) and nonresponders (<0.8 U/mL) were categorized and analyzed. Multivariable linear and logistic regression were used to estimate the correlation coefficient and odds ratio of response magnitude and status.

Results

Of 152 HSCT recipients, 141 (92.8%) were responders, with a median (interquartile range [IQR]) anti-S IgG titer of 2500 (107.9-2500) U/mL at a median (IQR) of 80.5 (36-153.5) days from last dose, regardless of the number of doses received. Higher quantitative titers were associated with receipt of more vaccine doses (coeff, 205.79; 95% CI, 30.10 to 381.47; P = .022), being female (coeff, 343.5; 95% CI, -682.6 to -4.4; P = .047), being younger (<65 years; coeff, 365.2; 95% CI, -711.3 to 19.1; P = .039), and not being on anti-CD20 therapy (coeff, -1163.7; 95% CI, -1717.7 to -609.7; P = .001). Being male (odds ratio [OR], 0.11; 95% CI, 0.01 to 0.93; P = .04) and being on anti-CD20 therapy (OR, 0.16; 95% CI, 0.03 to 0.70; P = .016) were associated with nonresponse.

Conclusions

Overall, most HSCT recipients had high SARS-CoV-2 antibody responses. More vaccine doses improved the magnitude of immune responses. Anti-S IgG monitoring may be useful for identifying attenuated vaccine-induced responses.

Specific immune response to mRNA vaccines against COVID-19 in patients receiving allogeneic stem cell transplantation for myeloid malignancy was altered by immunosuppressive therapy

BACKGROUND

Allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients are at high risk of complications associated with COVID-19 infection due to dysfunction of their immune system. Vaccination can protect from the adverse consequences of COVID-19. However, studies on the efficacy of COVID-19 vaccines in HSCT recipients with insufficient post-HSCT immune reconstitution are still scarce. In our study, we determined how immunosuppressive medication and the reconstitution of the cellular immune system influenced T cell responses specific for the surface glycoprotein of SARS-CoV-2 virus (S antigen) after two doses of mRNA vaccine against COVID-19 in patients with myeloid malignancies treated with HSCT.

METHODS

Vaccination outcomes were followed in 18 (allo-HSCT) recipients and 8 healthy volunteers. The IgG antibodies against SARS-CoV-2 spike (S) and nucleocapsid (NCP) protein were determined in ELISA and S-specific T cells were detected using a sensitive ELISPOT-IFNγ based on in vitro expansion and restimulation of T cells in pre- and post-vaccination blood samples. Multiparametric flow cytometry analysis of peripheral blood leukocyte differentiation markers was employed for determination of reconstitution of the main subpopulations of T cells and NK cells at month 6 after HSCT.

RESULTS

S- specific IgG antibody response detected in 72% of the patients was lower than in healthy vaccinees (100%). Vaccine-induced T-cell responses to S1 or S2 antigen were significantly reduced in HSCT recipients, which were treated with corticosteroids in dose 5 mg of prednisone- equivalents or higher during the vaccination period or in preceeding 100 days in comparison with recipients un-affected with corticosteroids. A significant positive correlation was found between the level of anti-SARS-Cov-2 spike protein IgG antibodies and the number of functional S antigen-specific T cells. Further analysis also showed that the specific response to vaccination was significantly influenced by the interval between administration of vaccine and transplantation. Vaccination outcomes were not related to age, sex, type of mRNA vaccine used, basic diagnosis, HLA match between HSC donor and recipient, and blood counts of lymphocytes, neutrophils, and monocytes at the time of vaccination. Multiparametric flow cytometry analysis of peripheral blood leukocyte differentiation markers showed that good humoral and cellular S-specific immune responses induced by vaccination were associated with well-reconstituted CD4⁺ T cells, mainly CD4⁺ effector memory subpopulation at six months after HSCT.

CONCLUSIONS

The results showed that both humoral and cellular adaptive immune responses of HSCT recipients to the SARS-CoV-2 vaccine were significantly suppressed by corticosteroid therapy. Specific response to the vaccine was significantly affected by the length of the interval between HSCT and vaccination. Vaccination as early as 5 months after HSCT can lead to a good response. Immune response to the vaccine is not related to age, gender, HLA match between HSC donor and recipient, or type of myeloid malignancy. Vaccine efficacy was dependent on well-reconstituted CD4⁺ T cells, at six months after HSCT.

Pre-Hematopoietic Stem Cell Transplantation Rituximab for Epstein-Barr Virus and Post-Lymphoproliferative Disorder Prophylaxis in Alemtuzumab Recipients

Epstein-Barr virus (EBV) reactivation and EBV-related post-transplantation lymphoproliferative disorder (PTLD) are often fatal complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The risk of EBV reactivation may be mitigated by depletion of B cells with rituximab. Starting in January 2020, allo-HSCT recipients undergoing T-cell depletion with alemtuzumab received 1 dose of rituximab before transplantation. The objective of this study was to evaluate the cumulative incidence of EBV reactivation and EBV-PTLD in recipients of allo-HSCT and in vivo T-cell depletion with alemtuzumab who received pre-HSCT rituximab compared to patients who did not. This was a single-center retrospective analysis of adult patients who consecutively received an HLA-identical allo-HSCT between January 2019 and May 2021 and in vivo T-cell depletion with alemtuzumab. Patients were included in the rituximab cohort if they received rituximab within 6 months before their transplantation. The primary endpoint was incidence of EBV reactivation at day 180 among those receiving pre-HSCT rituximab versus those not receiving rituximab. Secondary endpoints included cumulative incidence of EBV-PTLD at 1 year, time to engraftment, immune reconstitution, and incidence of infections and acute graft-versus-host disease (aGVHD) at day 180. Eighty-six consecutive patients who received an allo-HSCT with alemtuzumab T-cell depletion were reviewed; 43 patients who received pre-HSCT rituximab after our protocol modification were compared to 43 patients who did not receive pre-HSCT rituximab before this change. Median age was 57 (interquartile range [IQR] 40-69) years, and the majority of patients had acute myeloid leukemia or myelodysplastic syndrome. Baseline characteristics were similar between the cohorts. EBV reactivation at day 180 occurred in 23 (53%) patients without prior rituximab exposure versus 0 patients with pre-HSCT rituximab exposure (P < .0001). Similarly, 6 patients without prior rituximab exposure developed PTLD at 1 year compared to no cases of PTLD among patients receiving pre-HSCT rituximab. There was no difference in neutrophil engraftment, incidence of infections, or aGVHD at day 180 between the 2 cohorts. There was a delay in time to platelet engraftment in the rituximab cohort (median 16 [IQR 15-20] days versus 15 [IQR 14-17] days; P = .04). Administration of pre-HSCT rituximab before allo-HSCT in patients receiving T-cell depletion with alemtuzumab was associated with a significant decrease in the risk for EBV reactivation and EBV-PTLD, without increasing aGVHD or infection rates.

Allogeneic hematopoietic stem cell transplantation in the COVID-19 era

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

COVID-19 and HSCT (Hematopoietic stem cell transplant)

HSCT recipients are at increased risk for COVID-19-associated morbidity and mortality. Early treatment of symptomatic SARS-CoV-2 infection is an important means to decreasing risk for severe disease and death. While some HSCT recipients, particularly those who are early post-transplant and severely immunosuppressed, may have diminished response to COVID-19 vaccines, the benefits of vaccination are uncontested. Public health, healthcare facility and individual level approaches are all necessary to mitigate risk for infection in this vulnerable population.