Publication date: May 29, 2025

To investigate the association between mRNA COVID-19 vaccination and the risk of urticaria. Nationwide observational cohort study. Healthcare registers in Denmark. The vaccinated cohort included Danish residents aged ⩾5 years who received at least one dose of Comirnaty (Pfizer-BioNTech, BNT) or Spikevax (Moderna, MOD) in December 2020 to July 2023; the pre-pandemic (2017-19) general population aged ⩾5 years formed the comparator cohort. Urticaria-free participants were followed from the vaccination date until the earliest of the incident chronic or other types of urticaria diagnosis, COVID-19 infection, end of the 90-day outcome risk window, death, emigration, or October 2023. The expected number of urticaria events was computed using indirect standardisation of the pre-pandemic urticaria incidence rates. Standardised incidence ratios (SIRs) with corresponding 95% confidence intervals (CIs) were calculated overall and across sex, age and vaccine sequence-specific strata. We ascertained 4,700,301 vaccinated and 5,480,146 pre-pandemic comparators. Following all vaccine product sequences, SIRs (95% CI) were 0. 83 (0. 71-0. 96) for chronic urticaria and 1. 14 (95% CI 1. 03-1. 25) for other types of urticaria. Among MOD schedule adherers, the risk was three to fourfold increased for chronic (SIR 3. 00, 95% CI 2. 27-3. 88) and other types of urticaria (SIR 3. 65, 95% CI 3. 06-4. 31). Sensitivity analyses of dose specific effects confirmed a fourfold increased risk after MOD vaccine sequence but not BNT. Following the most recent mRNA vaccination dose, MOD vaccine schedule adherers had a higher than expected incidence of chronic and other types of urticaria. We found no association between BNT vaccination schedule and increased risk of urticaria.

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