The most important findings of this study can be summarised as follows: (1) in patients with RA and PsA treated with targeted therapy, COVID-19 vaccination is not associated with disease worsening, as assessed by categorised disease activity or arthritis flares; (2) however, when DAS28 variations were analysed as a continuous measure using a predictive model, patients treated with JAK-i or IL-6-i in RA and with IL-12/23-i in PsA showed greater disease activity as measured by DAS28 than those treated with TNF-i after COVID-19 vaccination. The gene discussed is IL6; the disease is rheumatoid arthritis.