Safety of SARS-CoV-2 vaccination in patients with Behcet's syndrome and familial Mediterranean fever: a cross-sectional comparative study on the effects of M-RNA based and inactivated vaccine.

Most of the published data relate to classical forms of rheumatic diseases (RD) and information on rare inflammatory disorders such as Behçet's syndrome (BS) and familial Mediterranean fever (FMF) is limited. We studied the frequency of side effects and disease flares after COVID-19 vaccination with either Pfizer/BioNTech or Sinovac/CoronaVac in 256 patients with BS, 247 with FMF, and 601 with RD. Telephone interviews were conducted using a questionnaire survey in a cross-sectional design in patients with BS, FMF, and RD followed by a single university hospital. Study participants were vaccinated either with CoronaVac (BS:109, FMF: 90, and RD: 343,) or BioNTech (BS: 147, FMF: 157 and RD: 258). The majority have received double dose (BS: 94.9%, FMF 92.3% and RD: 86.2%). BioNTech ensured a significantly better efficacy than CoronaVac against COVID-19 in all patient groups (BS: 1.4% vs 10.1%; FMF: 3.2% vs 12.2%, RD:2.7% vs 6.4%). Those with at least one adverse event (AE) were significantly more frequent among those vaccinated with BioNTech than those with CoronaVac (BS: 86.4% vs 45%; FMF: 83.4% vs 53.3%; and RD: 83.3% vs 45.5%). The majority of AEs were mild to moderate and transient and this was true for either vaccine. There were also AEs that required medical attention in all study groups following CoronaVac (BS: 5.5%, FMF: 3.3%, and RD:2.9%) or BioNTech (BS: 5.4%, FMF: 1.9%, and RD: 4.7%). The main causes for medical assistance were disease flare and cardiovascular events. Patients with BS (16.0%) and FMF (17.4%) were found to flare significantly more frequently when compared to those with RD (6.0%) (p < 0.001). This was true for either vaccine. BS patients reported mainly skin-mucosa lesions; there were however, 11 (4.3%) who developed major organ attack such as uveitis, thrombosis or stroke. Flare in FMF patients were associated mainly with acute serositis with or without fever. Arthralgia/arthritis or inflammatory back pain were observed mainly in the RD group. Our study demonstrates that BS and FMF patients vaccinated with either CoronaVac or BioNTech demonstrated similar AE profile and frequency compared to RD patients. AEs that required physician consultation or hospitalization occurred in all study groups after either CoronaVac or BioNTech. Increased frequency of flares in BS and FMF compared to that seen in RD might reflect defects in innate immunity and deserves further investigation. Caution should be required when monitoring these patients after vaccination.