Objectives Adolescents with juvenile-onset autoimmune inflammatory rheumatic diseases (AIIRD) could be at-risk for disease flare secondary to SARS-CoV-2 infection or to withholding anti-inflammatory therapy. While vaccination can protect against COVID-19, safety and immunogenicity data regarding anti-SARS-CoV-2 vaccines among adolescents with AIIRD are limited. This international, prospective, multicentre study evaluated the safety and immunogenicity of the BNT162b2 anti-SARS-CoV-2 vaccine among adolescents and young adults with juvenile-onset AIIRD, 80% of whom are on chronic immunomodulatory therapy. Methods Vaccine side effects, disease activity, and short-term efficacy were evaluated after 3 months in 91 patients. Anti-spike S1/S2 IgG antibody levels were evaluated in 37 patients and 22 controls, 2–9 weeks after the second dose. Results Ninety-one patients and 40 healthy controls were included. Safety profile was good, with 96.7% (n = 88) of patients reporting mild or no side-effects, and no change in disease activity. However, 3 patients had transient acute symptoms: 2 following the first vaccination (renal failure and pulmonary haemorrhage) and 1 following the second dose (mild lupus flare vs viral infection). Seropositivity rate was 97.3% in the AIIRD group compared with 100% among controls. However, anti-S1/S2 antibody titres were significantly lower in the AIIRD group compared with controls (242 ± 136.4 vs 387.8 ± 57.3 BAU/ml, respectively; p< 0.0001). No cases of COVID-19 were documented during the 3-month follow-up. Conclusion Vaccination of juvenile-onset AIIRD patients demonstrated good short-term safety and efficacy, high seropositivity rate, but lower anti-S1/S2 antibody titres compared with healthy controls. These results should encourage vaccination of adolescents with juvenile-onset AIIRD, even while on immunomodulation.

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