Although vaccination is widely accepted as an effective method of preventing and controlling the COVID‐19 pandemic, many people are concerned about possible cutaneous side‐effects, which can delay or prevent them from being vaccinated. The objectives of this systematic review were to assess the global prevalence and clinical manifestations of cutaneous adverse reactions following COVID‐19 vaccination. PubMed and Scopus databases were searched for articles published from 1 January 2019 to 31 December 2021, and reference lists for each selected article were screened. Case reports, case series, observational studies and randomized controlled trials that provided information on cutaneous adverse reactions following COVID‐19 vaccines were included. A total of 300 studies were included in a systematic review of which 32 studies with 946 366 participants were included in the meta‐analysis. The pooled prevalence of cutaneous manifestations following COVID‐19 vaccination was 3.8% (95% CI, 2.7%–5.3%). COVID‐19 vaccines based on the mRNA platform had a higher prevalence than other platforms at 6.9% (95% CI, 3.8%–12.3%). Various cutaneous manifestations have been reported from injection site reactions, which were the most common (72.16%) to uncommon adverse reactions such as delayed inflammatory reactions to tissue filler (0.07%) and flares of pre‐existing dermatoses (0.07%). Severe cutaneous reactions such as anaphylaxis have also been reported, but in rare cases (0.05%). In conclusion, cutaneous adverse reactions are common, especially in those receiving mRNA vaccines. Most reactions are mild and are not contraindications to subsequent vaccination except for anaphylaxis, which rarely occurs. COVID‐19 vaccination may also be associated with flares of pre‐existing dermatoses and delayed inflammatory reactions to tissue filler. Patients with a history of allergies, pre‐existing skin conditions or scheduled for filler injections should receive additional precounselling and monitoring. A better understanding of potential side‐effects may strengthen public confidence in those wary of new vaccine technologies.

Summary Patients who develop an immediate allergic reaction within the first 4 h of COVID‐19 vaccine injection are recommended not to receive the same vaccine again. This recommendation mainly focuses on the mRNA and adenoviral vector COVID‐19 vaccines, but data for whole virus vaccines are unknown. We report seven patients who developed an immediate reaction within 4 h (six had generalized urticaria, one had localized urticaria) after the first vaccination with CoronaVac, the inactivated SARS‐CoV‐2 vaccine. The results of skin tests and basophil activation tests suggested that spike peptides play a role in exacerbating urticaria in some patients. However, all subjects who developed urticaria within 4 h after CoronaVac vaccination were successfully revaccinated without graded challenge, although recurrent urticaria was common. This preliminary result indicates that acute urticaria alone should not be a contraindication for the second dose of CoronaVac if the supply of alternative vaccines is limited.

BackgroundAt present, no predictive models are available to determine the probability of in‐hospital mortality rates (HMRs) in all phenotypes of severe cutaneous adverse reactions (SCARs).ObjectivesOur study explored whether simple clinical and laboratory assessments could help predict the HMRs in any phenotypes of SCAR patients.MethodsFactors influencing HMRs in 195 adults diagnosed with different SCAR phenotypes were identified, and their optimal cut‐offs were determined by Youden's index. Predictive equations for HMRs for all SCAR patients and Stevens‐Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) patients were determined using the exact logistic regression models.ResultsAcute generalized exanthematous pustulosis (AGEP) patients were significantly older, with a short time from drug exposure to reaction, and higher neutrophil count compared to SJS/TEN and drug reaction with eosinophilia and systemic symptoms (DRESS, p < 0.001). Peripheral blood eosinophilia, atypical lymphocytosis and elevated liver transaminase enzymes were significantly higher in DRESS. SJS/TEN phenotype, age ≥ 71.5 years, neutrophil‐to‐lymphocyte ratio ≥ 4.08 (high NLR) and systemic infection were factors predicting in‐hospital mortality in all SCAR subjects. The ALLSCAR model developed from these factors demonstrated high‐diagnostic accuracy for predicting HMRs in all SCAR phenotypes (area under the receiver‐operator curve (AUC) = 0.95). The risk of in‐hospital death was significantly increased in SCAR patients with high NLR after adjusting for systemic infection. The model derived from high NLR, systemic infection and age yielded higher accuracy than SCORTEN (AUC = 0.77) for predicting the HMRs in SJS/TEN patients (AUC = 0.97).ConclusionsBeing older, having systemic infection, having a high NLR and SJS/TEN phenotype increases ALLSCAR scores, which in turn increases the risk of in‐hospital mortality. These basic clinical and laboratory parameters can easily be obtained in any hospital setting. Despite its simple approach, further validation of the model is warranted.

Urticaria is a common cutaneous adverse event from coronavirus disease 2019 vaccination. Previous studies hypothesized that excipients as polyethylene glycol in BNT162b2 vaccine and polysorbate in ChAdOx1 nCoV-19 vaccine are allergens. A 28-year-old woman had urticaria after a booster vaccination with BNT162b2 at the site of previous intradermal injection with severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) spike protein. This reaction emphasized that delayed urticaria may not be an allergic reaction to excipient but rather to the immunogen as such as SARS-CoV-2 spike protein.

Clinical applications of skin testing are known to help diagnose IgE-mediated and T-cell-mediated delayed cutaneous reactions. By contrast, drug-induced immune complex-mediated vasculitis is primarily diagnosed based on medical history, clinical setting and laboratory evidence of immune-complex formation, as there are no proven methods to identify the suspect culprit. We report three cases of drug- or biologic-induced immune complex-mediated vasculitis, in which the culprit agents could be confirmed by a positive intradermal test with later reading (between 12 and 24 h after the test), with verification by immunohistochemical or immunofluorescent results. The findings of our study suggest that skin tests with a delayed reading could have a potential role in diagnosing some instances of immune complex-mediated hypersensitivity reactions.