Safety and Immunogenicity of PCV20 in Pediatric Patients With Autoimmune Rheumatic Diseases

Will be defined as ≥2-fold increase in IgG titers for ≥50% of serotypes.

Blood samples will be collected at three time points: before the first dose (D0), 4 weeks after the first dose (D28), and six months after the final dose (D180). Functional opsonophagocytic anticapsular antibodies will be quantified using 6 validated serotype-specific opsonophagocytic activity (OPA) assays. Results will be expressed as geometric mean titers (GMTs) for each serotype and the percentage of participants reaching titers equal to or above the lower limit of quantification (LLOQ).

Safety will be closely monitored, and all serious adverse events will be classified as related or unrelated to the vaccine. A standardized adverse event diary will be provided to all patients and healthy controls for recording local and systemic reactions during the 4 weeks after first dose. Local reactions include: injection site pain, redness, swelling, bruising, itching, and induration. Systemic reactions include: fever, fatigue, chills, malaise, drowsiness, loss of appetite, nausea, vomiting, diarrhea, abdominal pain, dizziness, tremors, headache, fatigue, myalgia, muscle weakness, arthralgia, pruritus, and skin rash.

To evaluate the impact of PCV20 vaccination on clinical disease activity in patients with JIA, measured using JADAS27, higher scores indicate greater disease activity.

Unit of Measure: Score (0-57)

To evaluate the impact of PCV20 vaccination on clinical and laboratory disease activity in patients with juvenile systemic lupus erythematosus (jSLE), assessed using the SLEDAI-2K. The score incorporates clinical and laboratory manifestations of lupus, with higher scores indicating greater disease activity.

Unit of Measure: Score (range 0-105)

To evaluate the impact of PCV20 vaccination on clinical and laboratory disease activity in patients with juvenile dermatomyositis (JDM), assessed using the Childhood Myositis Assessment Scale (CMAS). The CMAS evaluates muscle function and endurance, with higher scores indicating better muscle strength and physical performance.

Unit of Measure: Score (range 0-52)

To assess the short- and long-term influence of immunosuppressive treatment on the response to PCV-20 vaccination in patients with ARDs compared to healthy controls.

Proportion of participants who achieve seroconversion defined as at least a twofold increase in pneumococcal serotype-specific IgG antibody concentrations compared to baseline at Days 28 and 180 following PCV20 vaccination.

Participants will be categorized as physically active or inactive based on World Health Organization criteria using validated methods.

Geometric mean titers of pneumococcal serotype-specific IgG antibodies will be quantified using multiplex Luminex assay at Days 28 and 180 after PCV20 vaccination.

Participants will be classified as physically active or inactive according to the World Health Organization criteria, based on validated methods.