Short and Long-term Immunogenicity and Safety Following the 23-valent Polysaccharide Pneumococcal Vaccine in Juvenile Idiopathic Arthritis Patients Under Anti-TNF Therapy

Seventeen JIA patients (International League Against Rheumatism criteria) followed at the Pediatric Rheumatology Unit of Children's Institute of Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo and who are refractory to methotrexate [median dose 0.9 mg/kg/week (0.7 - 1)] will be included immediately before the association of anti-TNF (etanercept 0.8 mg/kg/week, Group 1) to the previous therapy. The control group (Group 2) consist of 10 JIA patients on stable dose of methotrexate [median dose 0.8 mg/kg/week (0.3-1.0)]. One intramuscular dose of PPV23 (Sanofi Pasteur), lot B0381-3, at the immunization center of the same hospital will be given to each study subject.

Participants are ≥ 5 and ≤ 18 years old and patients with previous vaccination against S. pneumoniae will be excluded. This study was approved by the Local Ethical Committee of our University Hospital and an informed consent was obtained from all participants or their legal guardians.

Vaccine immunogenicity Blood samples will be collected pre-vaccination, 2 months and 12 months post-vaccination for 7 pneumoccocal serotypes (4, 6B, 9V, 14, 18C, 19F, 23F). Samples will be centrifuged and serum will be frozen and stored at -70 ◦C until tested. In order to eliminate non-specific antibodies that may exhibit cross-reactivity, the samples will be pre-absorbed with the C-polysaccharide and with the heterologous serotype 22F.

Serology for each serotype will be performed by enzyme immunoassay and immunogenicity endpoints will include seroprotection rate (SP) (percentage of subjects achieving antibodies titers ≥1.3 micrograms/mL), seroconversion rate (SC) (percentage of subjects with a minimum of 2-fold rise in post-vaccination antibodies titers) and the geometric mean concentration of antibodies (GMC). Adequate vaccine response will be considered when SC occur for at least 50% of all seven vaccine serotypes.

During the period of one year after PPV23 vaccination, all upper and lower respiratory tract infections will be weekly recorded during clinical appointments.