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

Covid-19 vaccination is recommended in allogeneic transplant recipients, but many questions remain regarding its efficacy. Here we studied serologic responses in 145 patients who had undergone allogeneic transplantation using in vivo T-cell depletion. Median age was 57 (range 21-79) at transplantation and 61 (range 24-80) at vaccination. Sixty-nine percent were Caucasian. One third each received transplants from HLA-identical related (MRD), adult unrelated (MUD), or haploidentical-cord blood donors. Graft-versus-host disease (GVHD) prophylaxis involved in-vivo T-cell depletion using alemtuzumab for MRD or MUD transplants and anti-thymocyte globulin for haplo-cord transplants. Patients were vaccinated between January 2021 and January 2022, an average of 31 months (range 3-111 months) after transplantation. Sixty-one percent received the BNT162b2 (bioNtech/Pfizer) vaccine, 34% received mRNA-1273 (Moderna), and 5% received JNJ-78436735 (Johnson & Johnson). After the initial vaccinations (2 doses for BNT162b2 and mRNA-1273, 1 dose for JNJ-7843673), 124 of the 145 (85%) patients had a detectable SARS-CoV-2 spike protein (S) antibody, and 21 (15%) did not respond. Ninety-nine (68%) had high-level responses (≥100 binding antibody units [BAU]/mL)m and 25 (17%) had a low-level response (<100 BAU/mL). In multivariable analysis, lymphocyte count less than 1 × 10⁹/ mL, having chronic GVHD, and being vaccinated in the first year after transplantation emerged as independent predictors for poor response. Neither donor source nor prior exposure to rituximab was predictive of antibody response. SARS-CoV-2 vaccination induced generally high response rates in recipients of allogeneic transplants including recipients of umbilical cord blood transplants and after in-vivo T cell depletion. Responses are less robust in those vaccinated in the first year after transplantation, those with low lymphocyte counts, and those with chronic GVHD.

Immunogenicity of a 5-dose pneumococcal vaccination schedule following allogeneic hematopoietic stem cell transplantation

The optimal schedule of pneumococcal vaccination after allogeneic hematopoietic stem cell transplantation (allo‐HSCT) remains controversial. The objective of this study was to investigate the immunogenicity of a 5‐dose pneumococcal vaccination schedule in adult allo‐HSCT recipients with and without immunosuppressive therapy. In this prospective cohort study, allo‐HSCT recipients received four doses of the 13‐valent pneumococcal conjugate vaccine (PCV13) and one dose of the 23‐valent pneumococcal polysaccharide vaccine (PPSV23) starting 4–6 months after allo‐HSCT. PCV13 was administered at T0, T1, T2, and T8 (T = months from enrollment) and PPSV23 at T10. Serum was collected at T0, T4, T8, T10, and T12, and IgG levels were measured for all 24 vaccine serotypes by immunoassay. The primary outcome was overall seroprotection at T12 defined as an IgG concentration ≥1.3 μg/ml for 17/24 vaccine serotypes in allo‐HCST recipients with and without immunosuppressive therapy at baseline. Secondary outcomes were serotype‐specific seroprotection and dynamics of IgG levels. We included 89 allo‐HSCT recipients in the final analysis. Overall seroprotection was 47% (15/32) for patients without immunosuppressive therapy at baseline versus 24% (11/46) for patients with immunosuppressive therapy (p = .03). Seroprotection was higher for PCV13 serotypes (78% and 54% respectively; p = .03) and lower for PPSV23‐unique serotypes (28% and 13% respectively; p = .1). IgG concentrations increased significantly over time for all 24 serotypes. Concluding, although immunogenicity of PCV13 serotypes was reasonable, the poor response to PPSV23 serotypes resulted in an insufficient overall response to pneumococcal vaccination for allo‐HSCT recipients. Research into vaccination strategies with higher‐valent T‐cell‐dependent pneumococcal vaccines is needed.

Infectious complications and vaccines

Infections are a major cause of morbidity and can result in mortality in long-term survivors after allogeneic hematopoietic cell transplantation. Chronic graft-versus-host disease and delayed immune reconstitution are recognized risk factors. Different strategies must be utilized depending on the individual patient's situation but include prolonged antimicrobial prophylaxis and vaccination. Some important infections due to pathogens preventable by vaccination are pneumococci, influenza, varicella-zoster virus, and SARS-CoV-2. Despite the fact that such recommendations have been in place for decades, implementation of these recommendations has been reported to be poor.

Changes in vaccination strategies contribute to the development of invasive pneumococcal disease in allogeneic hematopoietic stem cell transplantation recipients: a retrospective study for promoting vaccination

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients are at high risk of developing invasive pneumococcal disease (IPD) with substantial morbidity and mortality. Pneumococcal polysaccharide vaccine (PPSV23) and pneumococcal conjugate vaccine (PCV13) are the primary prevention strategy. The difference between the Japanese and international guidelines is limited except when to start PCV13. However, Japanese data regarding the incidence of IPD after allo-HSCT that include vaccination status are limited. Therefore, we aimed to study the clinical characteristics of patients with IPD following allo-HSCT, focusing on unvaccinated patients. We retrospectively reviewed allo-HSCT recipients between April 2005 and December 2018 at Komagome Hospital. Among 1,091 recipients, 11 (1008/100,000 recipients) developed 13 episodes of IPD. The median period from the first allo-HSCT to the first IPD episode was 686 days (10-3040 days). Ten patients developed IPD before vaccination, and seven of these unvaccinated patients with late-onset IPD were ineligible for vaccination based on domestic guidelines. Although appropriate treatments resulted in a good short-term prognosis, most episodes of IPD developed in unvaccinated allo-HSCT recipients. Our data support the promotion of better adherence to the current guidelines and the importance of pneumococcal vaccination even years after allo-HSCT to protect against late-onset IPD.