Incidence rates of bullous pemphigoid, herpes zoster and urticaria following the start of the COVID-19 vaccination programme in the UK: a population-based cohort study.

Abstract

Several population-based studies have reported an increased risk of serious skin conditions following COVID-19 vaccinations, but their population samples were not representative. Accurately estimating these risks is important for understanding vaccine hesitancy and improving clinical practice. To compare the incidence rates (IRs) of bullous pemphigoid (BP), herpes zoster (HZ) and urticaria before and after the UK's COVID-19 vaccination programme started. We conducted a population-based cohort study using electronic healthcare records from the Clinical Practice Research Datalink (1 January 2019-31 May 2023). We estimated monthly IRs (cases/100 000 person-years) for BP, HZ and urticaria. Using interrupted time series analysis, we compared changes in the IR slopes before and after the vaccine programme started (intervention). Sensitivity analyses were adjusted for COVID-19 lockdowns and total general practitioner (GP) appointments. In total, 16 156 639 adults (aged ≥ 18 years) registered at a general practice between 1 January 2019 and 31 May 2023 (BP, n = 3506; HZ, n = 129 668; urticaria, n = 63 320). The BP IR (cases/100 000 person-years) did not change postintervention vs. the preintervention period. We did not detect pre- and postintervention slopes. Sensitivity analysis results were similar. Preintervention, there was a downward slope for the HZ IR [-4.44, 95% confidence interval (CI) -5.54 to -3.35; P < 0.005]. The HZ IR increased postintervention vs. the preintervention period (5.15, 95% CI 3.43-6.88; P < 0.005). Despite the increase in the HZ IR, we found no evidence of a postintervention slope. Sensitivity analysis results were similar. Preintervention, there was a downward slope for the urticaria IR (-3.42, 95% CI -4.13 to -2.70; P < 0.005). The urticaria IR increased postintervention vs. the preintervention period (4.40, 95% CI 3.27-5.53; P < 0.005), resulting in an upward slope (0.98, 95% CI 0.43-1.52; P < 0.005). However, after accounting for lockdowns or GP appointments, the upward postintervention slope was no longer apparent. While the BP IR did not change following the COVID-19 vaccine programme in the UK, we detected increased IRs for HZ and urticaria. However, these increases were modest, and, for many, the benefits of vaccination will probably outweigh the potential risks. Future research should use individual patient-level studies (e.g. self-controlled case series) to determine whether the increases in HZ and urticaria IRs are driven by COVID-19 vaccines.