Pneumococcal vaccination for splenectomized patients with thalassemia major in Indonesia

Antibody Response against Vaccine Antigens in Children after TCRαβ-Depleted Haploidentical Stem Cell Transplantation: Is It Similar to That in Recipients with Fully Matched Donors?

Recipients of hematopoietic stem cell transplantation (HSCT) with HLA-mismatched donors are more immune suppressed than those with fully matched donors. The immunologic response to vaccines also may differ in HLA-mismatched haploidentical HSCT recipients. In this study, we aimed to evaluate the antibody response to vaccines in pediatric TCRαβ-depleted haploidentical HSCT recipients. This longitudinal study included a study group of 21 children who underwent haploidentical HSCT without CD19 depletion and with TCRαβ depletion and a control group of 38 children who underwent fully matched donor HSCT. Antibody levels were quantified by serologic tests before vaccination and after each dose against tetanus, diphtheria, pneumococcus, hepatitis B, hepatitis A, measles, rubella, mumps, and varicella. The median recipient age was significantly lower (P = .037) and the median donor age was significantly higher (P = .000) in the haploidentical group compared with the fully matched group. At the months 1, 3, 6, 9 and 12 post-transplantation, the median CD4, CD8, and CD19 cell counts and lymphocyte counts were similar in the haploidentical and fully matched groups. The median natural killer cell count was higher in the haploidentical group at the months 1, 3, and 6 post-transplantation (P = .001, .006, and .004, respectively). The median time to first vaccination was similar in the 2 groups (12.5 [range, 11 to 14] months for the haploidentical group and 11 [range, 9 to 13] months for the fully matched group; P = .441). Seroprotection rates were 100% in both groups after the second and third doses of diphtheria vaccine, the third dose of tetanus vaccine, the third dose of hepatitis B vaccine, the second and third doses of pneumococcal conjugate vaccines (PCV13), and pneumococcal polysaccharide vaccine (PSPV23), although lower after the initial doses and before vaccination. Seroprotection for hepatitis A, rubella, and varicella was >90% in the fully matched group and 100% for the haploidentical group after the second doses. Measles and mumps seroprotection rates were >80% in the haploidentical group and approximately 70% for the fully matched group after the second dose. Antibody response and seroprotection rates against vaccine antigens were similar in the haploidentical group and the fully matched when revaccination was started at 12 months post-transplantation. These findings support the idea that TCRαβ-depleted haploidentical HSCT recipients can be revaccinated according to the same vaccination schedule as fully matched HSCT recipients. Revaccination earlier after transplantation and vaccine responses for recipients of different types of HSCT should be evaluated in future studies.

Efficacy, immunogenicity, and evidence for best-timing of pneumococcal vaccination in splenectomized adults: a systematic review

INTRODUCTION

: Streptococcus pneumoniae is the most frequent cause of overwhelming post-splenectomy infections. Pneumococcal vaccination is generally recommended for splenectomized individuals. However, most of our knowledge comes from a few observational studies or small randomized clinical trials. We conducted this systematic review to assess the evidence of efficacy, antibody response, and the best timing for pneumococcal vaccination in splenectomized individuals.

AREAS COVERED

: The systematic review was conducted according to the PRISMA guidelines. We screened 489 articles, included 21 articles, and assessed the risk of bias using Cochrane RoB 2 and ROBINS-I. We summarized the findings narratively due to the heterogeneity of the studies.

EXPERT OPINION

Splenectomized individuals seem to have adequate antibody responses to pneumococcal vaccines. No differences in antibody responses were observed compared to healthy controls, except in one study. The studies were heterogeneous, and the majority had moderate to high degree of bias. There is a lack of clinical evidence for efficacy and best timing of pneumococcal vaccination in splenectomized individuals. Randomized clinical trials addressing these issues are needed.

Perioperative Immunization for Splenectomy and the Surgeon's Responsibility: A Review

Importance

Patients who have had splenectomy have a lifelong risk of overwhelming postsplenectomy infection (OPSI), a condition associated with high mortality rates. Surgeons must be aware of the rationale of vaccination in the case of splenectomy, to provide appropriate immunization in the perioperative time.

Observations

English-language articles published from January 1, 1990, to December 31, 2019, were retrieved from MEDLINE/PubMed, Cochrane Library, and ClinicalTrials.gov databases. Randomized clinical trials as well as systematic reviews and observational studies were considered. Asplenia yields an impairment of both innate and adaptive immunity, thus increasing the risk of severe encapsulated bacterial infections. Current epidemiology of OPSI ranges from 0.1% to 8.5% but is hard to ascertain because of ongoing shifts in patients' baseline conditions and vaccine penetration. Despite the lack of randomized clinical trials, immunization appears to be effective in reducing OPSI incidence. Unfortunately, vaccination coverage is still suboptimal, with a great variability in vaccination rates being reported across institutions and time frames. Notably, current guidelines do not advocate any particular health care qualification responsible for vaccine prescription or administration. Given the dearth of high-level basic science or clinical evidence, the optimal vaccination timing and the need for booster doses are not yet well established. Although almost all guidelines indicate to not administer vaccines within 14 days before and after surgery, most data suggest that immunization might be effective even in the immediate perioperative time, thus placing the surgeon in a primary position for vaccine delivery. Furthermore, revaccination schedules are the target of ongoing debates, since a vaccine-driven hyporesponsiveness has been postulated.

Conclusions and Relevance

In patients who have undergone splenectomy, OPSI might be effectively prevented by proper immunization. Surgeons have the primary responsibility for achieving adequate, initial immunization in the setting of both planned and urgent splenectomy.