New onset and flare of rheumatic diseases following COVID-19 vaccination are mild and respond well to treatment: 9-month follow-up data from a single centre cohort.

Anti-COVID-19 vaccines have proved to be effective and well tolerated. Great attention is now being paid to the characterisation of possible adverse events associated to their administration. We report a case series of suspected rheumatic diseases (RDs) following anti-COVID-19 vaccination. We included patients evaluated at first-aid rheumatologic consultancy and at rheumatologic outpatient and inpatient clinic at Padova University Hospital between May and September 2021 presenting with a RD within 30 days after an anti-COVID-19 vaccine dose. Our selection was in accordance with the World Health Organisation guidelines for adverse event following immunisation (AEFI) surveillance. Patients were regularly re-evaluated by telemedicine or face-to-face visit. We identified 30 cases of RD following vaccination: 24 (80.0%) new onsets and 6 (20.0%) flares. Most of patients (76.6%) received the BNT162b2 vaccine. The mean time to RD onset/flare was 12±9 days. The most common manifestations were inflammatory arthritis (40.0%), rheumatic polymyalgia (33.3%) and adult-onset Still's disease (13.3%). At the last FU visit (9.6±2.2 months), 83.3% of patients showed complete response to first- or second-line therapy, 13.3% a partial response and one patient (3.3%) was still experiencing an active disease. Considering the amount of vaccine doses administered during the evaluation period we overall detected a limited number of cases. We noted a clear prevalence of autoinflammatory conditions and seronegative manifestations. The great majority of patients had mild features and showed a good response to therapy.