Background Hepatitis B is a vaccine preventable disease with intermediate endimicity in Greece . National vaccination against Hepatitis B Virus (HBV) was introduced in 1998; however approximately 10% of the population fails to mount an appropriate immune response. JIA patients on immunosuppressive therapy, such as anti-TNFa, are prone to infection or reactivation of HBV .
Objectives The aim of this study is to define the immune status against HBV in children presenting with JIA.
Methods Cross sectional prospective single centre study including 89 newly diagnosed JIA patients and 89 healthy controls matched for age and gender. All participants were vaccinated against HBV in infancy (3 doses). Sera were tested for hepatitis B surface antigen (HBsAg), hepatitis B core antibody (anti-HBc), and anti-HBs. Patients with anti-HBs titers ≥10 IU/L were considered to be immune. Data were analyzed with SPSS 10.0 version.
Results Eighty nine JIA patients included in the study (23 males), with a mean age of 6.7 years (range 1.5-13). None of the patients or the controls was positive for HBsAg or anti-HBc. The proportion of JIA patients with evidence of HBV immunity was significantly lower than their healthy counterparts. In the JIA group 56% (49/89) were HBV immune (anti-HBs level ≥10 IU/L) while in the control group 92% (82/89) were immune against HBV (p<0.005). Antibody levels in the patient group were significantly lower compared to the control group. The mean concentration of anti-HBs levels in JIA patients was 18.9 IU/L versus 83.2 IU/L in the control group (p<0.005). Diagnosis of JIA and older age were associated with the absence of protective antibodies. The type of JIA or the type of vaccine given in infancy did not affect adequate antibody response.
Conclusions Our study showed that a significant percentage of JIA patients due to start immunomodulating treatment do not have protective antibody levels against HBV. This could be attributed to the immune dysregulation noted in patients with autoimmune diseases. Larger studies are needed to explore this hypothesis. Earlier studies have shown that the majority of previously unvaccinated children on immunosuppressantshave an adequate response to hepatitis B vaccination ; it is not clear however if a booster dose would be sufficient in children already immunized. Although there is no evidence to support the introduction of a booster HBV dose in healthy children who mount low antibody response following immunization , further studies are required to address this question in patients with JIA.
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Disclosure of Interest None Declared