The effect of splenectomy on the levels of PCV-13-induced memory B- and T cells

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.

Establishment of an ELISpot Assay to Detect Cellular Immunity against S. pneumoniae in Vaccinated Kidney Transplant Recipients

In organ transplant recipients, the rate of invasive pneumococcal diseases is 25 times greater than in the general population. Vaccination against S. pneumoniae is recommended in this cohort because it reduces the incidence of this severe form of pneumococcal infection. Previous studies indicate that transplant recipients can produce specific antibodies after pneumococcal vaccination. However, it remains unclear if vaccination also induces specific cellular immunity. In the current study on 38 kidney transplant recipients, we established an interferon-γ ELISpot assay that can detect serotype-specific cellular responses against S. pneumoniae. The results indicate that sequential vaccination with the conjugated vaccine Prevenar 13 and the polysaccharide vaccine Pneumovax 23 led to an increase of serotype-specific cellular immunity. We observed the strongest responses against the serotypes 9N and 14, which are both components of Pneumovax 23. Cellular responses against S. pneumoniae correlated positively with specific IgG antibodies (r = 0.32, p = 0.12). In conclusion, this is the first report indicating that kidney transplant recipients can mount specific cellular responses after pneumococcal vaccination. The ELISpot we established will allow for further investigations. These could help to define, for example, factors influencing specific cellular immunity in immunocompromised cohorts or the duration of cellular immunity after vaccination.

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.