Chronic spontaneous urticaria after BNT162b2 mRNA (Pfizer-BioNTech) vaccination against SARS-CoV-2

Background: The factors that trigger and exacerbate chronic spontaneous urticaria (CSU) are well known, but it is not unclear whether messenger RNA (mRNA) vaccination against severe acute respiratory syndrome coronavirus 2 can trigger new cases of CSU or a relapse of CSU after long-term remission. Objective: To study the clinical cases of patients with new-onset CSU and CSU in remission who relapsed within 3 months after BNT162b2 mRNA vaccination. Methods: All patients with a CSU diagnosis within 12 weeks of BNT162b2 mRNA vaccination were retrospectively identified and included in the new-onset CSU and the relapsed CSU groups. The first control group (CSU control group) retrospectively consisted of patients diagnosed with CSU in complete clinical remission for ≥ 6 months, with no CSU relapse after vaccination. The second control group (healthy control group) consisted of subjects who were fully vaccinated and without CSU, matched 1:2 for age and sex with patients with CSU. Results: Twenty-seven patients were included in the relapsed CSU group, 32 patients in the new-onset CSU group, 179 patients in the CSU control group, and 476 subjects in the healthy control group. The relapsed CSU and new-onset CSU groups had more allergic comorbidities overall (19 [70.4%] and 13 [40.6%], respectively) than the CSU control group and the healthy control group (50 [27.9%] and 110 [23.1%], respectively; p < 0.001). Multiple logistic regression analysis showed that a positive autologous serum skin test result, overall allergic comorbidities, and basopenia were positively associated with the probability of CSU relapse within 3 months after BNT162b2 mRNA vaccination (odds ratio [OR] 5.54 [95% confidence interval {CI}, 2.36-13.02], p < 0.001); OR 6.13 [95% CI, 2.52-14.89], p = 0.001; and OR 2.81 [95% CI, 1.17-6.72, p = 0.020, respectively). Conclusion: It is possible that BNT162b2 mRNA vaccination serves as a provoking and/or relapsing factor of CSU in individuals with allergic diseases and/or predisposed autoimmunity.