Connolly CM, Ruddy JA, Boyarsky BJ, et al. - Disease flare and post vaccination reactions (reactogenicity) following 2-dose SARS–CoV-2 messenger RNA (mRNA) vaccination were evaluated in patients with rheumatic and musculoskeletal diseases (RMDs).

• A total of 1,377 RMD patients who received 2-dose SARS–CoV-2 mRNA vaccination provided responses to questionnaires detailing local and systemic reactions experienced within 7 days of each vaccine dose (dose 1 and dose 2), and 1 month after dose 2, detailing any flares of RMD.

• Flares requiring treatment were reported in 11% of the patients.

• Prior SARS–CoV-2 infection, flares in the 6 months preceding vaccination, and the use of combination immunomodulatory therapy were noted to be associated with occurrence of flares.

• Local and systemic reactions occurring most frequently were injection site pain (87% after dose 1, 86% after dose 2) and fatigue (60% after dose 1, 80% after dose 2).

• After dose 2, increase in reactogenicity occurred, particularly for systemic reactions.

• There appeared no interference of local and systemic reactions in daily activity.