Immunogenicity of influenza vaccination in paediatric rheumatic diseases

Background Data on the long-term immunogenicity of influenza vaccination in paediatric rheumatic diseases remain limited. This study compared immunogenicity and 6-month antibody persistence against influenza A (H3N2) and influenza B (Yamagata) following seasonal inactivated influenza vaccination in patients with autoimmune diseases and healthy controls (HCs). Methods In this prospective cohort study, patients with juvenile idiopathic arthritis, childhood-onset systemic lupus erythematosus, or idiopathic inflammatory myopathies and HCs received a single dose of quadrivalent inactivated influenza vaccine. Serum samples were collected at baseline and 1 and 6 months post-vaccination. Haemagglutination inhibition (HI) and neutralization (NT) assays measured antibody responses against influenza A (H3N2) and influenza B (Yamagata). Outcomes included seroprotection, seroconversion, propensity score-adjusted geometric mean titres (GMTs), and factors associated with 6-month influenza A (H3N2) antibody responses using multivariable linear regression. Results A total of 120 participants, including 110 patients and 10 HCs, were enrolled. At 1 month, no significant differences were observed in seroprotection, seroconversion, or GMTs against influenza A (H3N2) or influenza B (Yamagata) between patients and HCs. At 6 months, patients had significantly lower adjusted HI GMTs against influenza A (H3N2) than HCs (171.9 [95% CI 133.8–220.9] vs 360.4 [190.2–682.8]; p = 0.035), with similar findings for NT GMTs (274.1 [198.8–377.8] vs 749.3 [358.8–1564.8]; p = 0.014). HI and NT GMTs against influenza B (Yamagata) did not differ significantly between groups. Baseline influenza A (H3N2) antibody titre was the only independent predictor of 6-month antibody responses in multivariable analysis. Conclusions Patients with paediatric rheumatic diseases developed antibody responses to influenza A (H3N2) and influenza B (Yamagata) 1 month after vaccination, with no statistically significant differences from HCs. However, antibody persistence against influenza A (H3N2) was significantly lower at 6 months, whereas no statistically significant difference was observed for influenza B (Yamagata).