Natural immunity against Haemophilus influenza type B in splenectomised Beta-thalassaemia children.

Patients with beta-thalassaemia major and asplenia have an increased risk of encapsulated bacterial infections. The aim of this study was to determine the Haemophilus influenza type b (Hib) antibody concentrations in beta-thalassaemia patients with or without spleens. The Hib antibody concentrations were investigated in 850 patients with thalassaemia major, of whom 437 had undergone splenectomy. Hib antibody levels equal or greater than 1.0 μg mL(-1) were classified as long-term protection, those between 0.15 and less than 1.0 μg mL(-1) as short-term protection and those less than 0.15 μg mL(-1) as no protection. The mean Hib antibody level was lower in asplenic subjects than in non splenectomised subjects (0.39 ± 0.5 vs. 1.08 ± 0.55 μg mL(-1), p < 0.001). The protective antibody level prevalence in asplenic patients was significantly lower than that in patients with spleens (32.3% vs. 85.7%, p < 0.001). Protection against Hib decreased as the time interval after splenectomy increased from 57.2% at a less than 60 months interval to 10.8% at a greater than 120 months interval (p = 0.001). Nearly 30% of the 437 splenectomised subjects had long-term protection against Hib, whereas 64.4% of the 413 non splenectomised subjects had long-term protection (p < 0.001). Asplenic subjects had lower Hib antibody levels than non splenectomised subjects. Additionally, the antibody levels decreased as the time interval increased after splenectomy. A Hib vaccine recommendation for splenectomised thalassaemia major seems essential.