Flares of mixed cryoglobulinaemia vasculitis after vaccination against SARS-CoV-2

Studies on the safety and immunogenicity of SARS-CoV-2 vaccination in patients with inflammatory rheumatic diseases have so far not included mixed cryoglobulinaemia (MC) vasculitis.1–3 We report a prospective observational multicentre study on this disorder. Participants were followed at four tertiary referral centres and were instructed to promptly inform the attending physicians about unusual events felt as possibly related to vaccination. Seventy-one patients were recruited: they had infection-cured hepatitis C virus (HCV)-related MC, either uncomplicated (HCV-MC, n=50) or complicated by low-grade non-Hodgkin’s lymphoma (MC-NHL, n=8), or essential MC (EMC, n=13). The characteristics of the patients, exclusion criteria and definition of bona fide vaccination-related flare are described in online supplemental methods.### Supplementary data [annrheumdis-2021-221248supp001.pdf] Overall, 9 of 71 (12.7%) patients had postvaccination MC vasculitis flare. However, 8 of 71 patients had experienced within 12 months before vaccination spontaneous flares, where 7 cases required rituximab and 3 of them (37.5%) had postvaccination flare (see online supplemental information). Thus, to exclude the confounding effects of high proneness to spontaneous flare as the facilitator and of rituximab as the preventor, we further restricted the evaluation of postvaccination flare rate to 63 patients off-therapy and without spontaneous flares for 20–48 months before …