Immunogenicity 6 months post COVID-19 mRNA vaccination among adolescents with juvenile idiopathic arthritis on treatment with TNF inhibitors

Objectives Mass vaccination is the most effective strategy for controlling the COVID-19 pandemic. This study aimed to evaluate the 6-month immunogenicity after BNT162b2-COVID-19 vaccination in adolescents with JIA on TNFi treatment. Methods This single-centre study included adolescents with JIA treated with TNFi for at least 18 months. Patients received two doses of COVID-19 vaccine (Pfizer-BioNTech) from 15 April to 15 May 2021. Quantitative measurement of IgG antibodies to SARS-CoV-2-spike-protein-1 was performed at 1, 3 and 6 months post-vaccination. Results Overall, 21 adolescents with JIA in clinical remission at the time of vaccinations were enrolled. None of them discontinued TNFi/MTX treatment at the time of vaccine administration or during the follow-up period. All patients developed a sustained humoral response against SARS-CoV-2 at 1 and 3 months after vaccination (P < 0.05). The antibody levels decreased significantly at 6 months post-vaccination (P < 0.01). The type of JIA did not reveal any differences in the humoral response at 3 (P = 0.894) or 6 months post-vaccination (P = 0.72). No difference was detected upon comparison of the immunogenicity between the different treatment arms (adalimumab vs etanercept) at 3 (P = 0.387) and 6 months (P = 0.526), or TNFi monotherapy vs combined therapy (TNFi plus methotrexate) at 3 (P = 0.623) and 6 months (P = 0.885). Conclusions Although mRNA vaccines develop satisfactory immunogenicity at 1 month and 3 months post-vaccination in adolescents with JIA on TNFi, SARS-CoV-2 antibody titres decrease significantly overtime, remaining at lower levels at 6 months. Further collaborative studies are required to determine long-term immunogenicity, real duration of immune protection and the need for a booster vaccine dose.