Safety of the BNT2b2 vaccine
The safety profile of the 3 vaccine doses was favourable, with most participants experiencing either no or mild side-effects (Table 2). Local reactions to vaccination were more common among AIIRD patients compared with controls at 2–8 weeks after the second vaccination, 71% (n=88) and 55% (n=44), p=0.0293, respectively; whereas after the third vaccine dose, AIIRD patients had significantly fewer local reactions than controls did, 39% (n=25) vs. 73% (n=22), p=0.004, respectively. The prevalence of systemic side-effects was comparable between patients with AIIRD and controls. The most common systemic side-effects were fatigue, myalgia, headache and arthralgia, with a comparable prevalence among AIIRD patients and controls. Importantly, there were no serious side-effects in either group. No cases of pericarditis or myocarditis were observed. Five patients (4%) experienced an exacerbation of rheumatic disease shortly after the first vaccine dose and 3 patients (2%) after the second dose. Two patients, both with AAV, were hospitalized shortly after the first vaccine dose, as previously reported by our group. None of the patients who received the third vaccine reported subsequent rheumatic disease exacerbation or hospitalization. Disease activity remained stable at 1-year clinical follow-up in all patients.