Maintenance of antibody response to diphtheria/tetanus vaccine in patients aged 2–5 years with polyarticular-course juvenile idiopathic arthritis receiving subcutaneous abatacept

Abstract Background Patients with polyarticular-course juvenile idiopathic arthritis (pJIA), receiving disease-modifying anti-rheumatic drugs with immunosuppressive effects, may be at increased risk of vaccine-preventable infections. This substudy assessed protective antibody responses to diphtheria and tetanus vaccination given prior to study enrolment in patients with pJIA. Findings This was a substudy of a 24-month, single-arm, open-label, multicenter, Phase III trial (NCT01844518) of subcutaneous abatacept in children with active pJIA (N = 219). Patients aged 2–5 years, with ≥2 continuous months of weekly weight-tiered (10– 0.1 IU/mL), and safety, were assessed. Overall, 29 patients were analyzed: 19 (65.5%), 1 (3.4%) and 9 (31.0%) patients had > 12, 6–12 and 2–