Adherence to vaccination guidelines of patients with complete splenectomy in Norway, 2008-2020

The spleen is responsible for blood filtration and mounting an immune response against pathogens. In some people the spleen must be surgically removed because of traumatic events or oncological and hematological conditions. These patients are at higher risk of developing diseases caused by encapsulated bacteria throughout their lives. Thus, immunisations are advised for splenectomised persons to prevent infection caused by Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae type b (Hib). This study assessed vaccination coverage (VC) among Norwegian patients with surgical asplenia. Using the Nomesco Classification of Surgical Procedures codes, patient information (age, sex, date of initial diagnosis and date of surgery) was acquired from the Norwegian Patient Registry. The National Immunization Register provided information on vaccination status and data of any subsequent invasive bacterial infections were obtained from the Norwegian Surveillance System for Communicable Diseases. From the total population of Norway, 3155 patients who had undergone complete splenectomy were identified. Of these, 914 (29.0%) had received at least one dose of pneumococcal conjugate vaccine (PCV), 1324 (42.0%) at least one dose of pneumococcal polysaccharide vaccine and 589 (18.7%) had received both. Only 4.2% of the patients had received two doses of a meningococcal ACWY conjugate vaccine, while 8.0% of 1467 patients splenectomised after 2014 had received at least two doses of a serogroup B meningococcal vaccine. The VC for Hib was 18.7%. Nearly all splenectomised children under the age of 10 were vaccinated with Hib and PCV as these vaccines are included in the childhood immunisation program. For all vaccines, VC decreased with age. Twenty-nine invasive bacterial infections were registered post-splenectomy in 25 patients. Vaccination according to national recommendations could have prevented at least 8 (28%) of these infections. Our study showed that efforts are required to increase VC of splenectomised individuals in Norway.