Compliance with Immunizations in Splenectomized Individuals: A Study of the Splenectomized Hereditary Spherocytosis Population
Authors: Grace Rachael F. , Mednick Rachel E. , Neufeld Ellis J. 
Published: April 2020

Abstract
Overwhelming infection by encapsulated bacteria is a significant short- and longterm risk of splenectomy. Vaccines are available for organisms to which asplenic patients are susceptible, i.e. S. pneumoniae, N. meningitidis, and H. influenza-B. Therefore, strict adherence to the immunizations against these organisms is recommended. In addition, after splenectomy, antibiotic prophylaxis is advised, although guidelines for chemoprophylaxis are not consistent across hematology and surgical disciplines.
METHODS: We performed a cross sectional study to determine immunization status, antibiotic use, and patient knowledge after splenectomy in the hereditary spherocytosis (HS) population. Subjects were ascertained from the recent and archival records of the hematology, surgery, and pathology departments at Children’s Hospital Boston. Addresses of former patients were sought by public record review and through current patient/family members. A strategy of expanding families by phone contact for this genetic disorder (commonly autosomal dominant) allowed ascertainment of older relatives of current patients. Vaccine status was by self- or parental-report.
RESULTS: We enrolled 77 splenectomized HS patients (38% male, mean age 34.7 y, mean age at splenectomy 10.9 y). Of the asplenic HS patients interviewed, only 20 (26%) reported receiving all of the recommended post-splenectomy vaccines (Table 1). However, 65% of splenectomized individuals reported that a physician had told them that their immunizations were up-to-date. Among the asplenic HS patients, the likelihood of receiving a particular vaccine was related to the number of years the vaccine had been available: PPV23 vaccine (1977) 96% &gt; MPSV4 (1981) 78% &gt; Hib (1987) 64% &gt; PCV7 (2000) 42% &gt; MCV4 (2005) 27%. As expected, asplenic patients &lt; age 20 y were much more likely to have received the new conjugate vaccines than older adults (PCV 83% vs. 23%, P&lt;0.001; MCV4 87% vs. 17%, P&lt;0.001; Hib 96% vs. 52%; P&lt;0.001). Of the 77 splenectomized individuals, 44 stated that they had taken prophylactic antibiotics following splenectomy. Of these 44, 25% stopped prophylaxis within the year of splenectomy. There were 14 reported cases of serious infection (sepsis, bacterial meningitis, or bacterial pneumonia) in splenectomized patients. Of these, 2/14 were up-to-date for immunizations. 13 of the 93 unsplenectomized individuals experienced serious infection (difference N.S.). 22 of 77 splenectomized patients interviewed were unaware of their immunization status, and approximately 75% of patients were not up-to-date on all currently recommended vaccinations. These numbers may reflect lack of patient knowledge about the risk of infection following splenectomy, and they demonstrate room for substantial improvement in pre-and post-splenectomy management of HS patients, whose splenectomies are virtually always planned and elective. Preoperative immunization is key, and pediatric hematology clinics have a unique opportunity to ascertain and provide catch-up and booster vaccinations to splenectomized adult relatives of their patients. A greater effort must be made by hematologists, primary care providers, and surgeons to educate patients about the risks of splenectomy, and the positive contributions that immunizations provide in protecting asplenic individuals from infection.
Table 1. Summary of adherence to immunizations
PCV7 PPV23 MCV4 MPSV4 Influenza Hib All Recommended Immunizations PCV7, Pneumococcal Conjugate Vaccine; PPV23, Pneumococcal Polysaccharide Vaccine; MCV4, Meningococcal Conjugate Vaccine; MPSV4, Meningococcal Polysaccharide Vaccine; Hib, Haemophilus influenza Type B Conjugate Vaccine 32/77 74/77 21/77 60/77 67/77 49/77 20/77