Influence of Methotrexate Discontinuation on Immunogenicity After PCV-20 Vaccine in Patients ARDs

Inclusion Criteria: * Adults (\>=18 years ) with confirmed ARD diagnosis (e.g., RA, PsA, axial SpA, primary Sjögren's, SLE, IIM, SSc, MCTD). * Stable MTX dose ≥12 weeks. * Prednisone ≤5 mg/day. * Low disease activity/remission according to specific disease activity criteria. * Eligible for PCV20 vaccination (no prior PCV20). Exclusion Criteria: * Anaphylaxis to vaccine components. * Acute febrile illness. * Guillain-Barré, decompensated CHF (NYHA III-IV), demyelinating disease. * Live virus vaccine ≤4 weeks or inactivated vaccine ≤2 weeks before. * Blood products in last 6 months. * Severe infection in last month (including pneumococcal). * Hospitalization at enrollment. * Refusal to participate or inability to complete study procedures.