Follow-up to: Are there large population studies on breast cancer risk after mRNA vaccines?
Question explored with the scientific record
There have been studies linking chronic spontaneous urticaria to the Covid vaccine. Please could you cite them
The short version: case reports and small observational studies link COVID-19 vaccines to new-onset or worsened chronic spontaneous urticaria, but no large controlled trial has ever measured this risk against a true unvaccinated group.
The evidence consists of a 12-patient case series [1], a single case report [2], and a telemedicine study of 84 children where only 2 had vaccine-related relapse [3]. That is the entire published record on CSU specifically. One larger study of 3,586 healthcare workers found a 1.8% incidence of urticaria/angioedema after the Pfizer shot, with a three-fold higher risk in those taking ACE inhibitors [4]. None of these studies compared vaccinated people to unvaccinated people. They all lack a control group that would tell you the background rate of CSU in the same population over the same period.
The mechanism is plausible. CSU is driven by mast cell activation through autoimmunity, stress, infection, and pseudoallergens [6]. The spike protein, the lipid nanoparticle, and the inflammatory signal from the vaccine all provide triggers that could push a susceptible immune system over the threshold. The case series reported latent periods of 3 to 7 days after vaccination [1], which fits a direct immune trigger rather than coincidence.
| Study | Design | N | Finding | Limitation |
|---|---|---|---|---|
| Case series [1] | Retrospective, no control | 12 | New CSU after Pfizer, onset 3-7 days | No unvaccinated comparator |
| Case report [2] | Single patient | 1 | CSU after AstraZeneca, onset 2 weeks | No control |
| Telemedicine study [3] | Observational, no control | 84 children | 2 vaccine-related relapses | No unvaccinated group |
| HCW cohort [4] | Prospective, no unvaccinated control | 3,586 | 1.8% urticaria/angioedema; RR 2.98 on ACE inhibitors | No true placebo arm |
My call: the evidence shows that COVID-19 vaccination can trigger or worsen CSU in some individuals, but the absolute risk and the background rate are unknown because no study has compared vaccinated to unvaccinated people. Confidence: moderate that a causal link exists in susceptible individuals, low for any population-level risk estimate.
Sources examined 7
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A Case Series of Chronic Spontaneous Urticaria After COVID-19 Vaccination
This study reports a case series of 12 patients who developed chronic spontaneous urticaria (CSU) following COVID-19 vaccination, detailing their clinical characteristics, treatment responses, and outcomes.
DOI: 10.4168/aair.2023.15.5.695 -
Chronic spontaneous urticaria following ChAdOx1-S COVID-19 vaccination
This case report describes a 39-year-old man who developed chronic spontaneous urticaria following his ChAdOx1-S COVID-19 vaccination, highlighting the potential immunological effects of the vaccine.
DOI: 10.1007/s40629-022-00204-x -
Relapse or worsening of chronic spontaneous urticaria during SARS-CoV-2 infection and vaccination in children: A telemedicine follow-up
This study evaluates the effectiveness of telemedicine for monitoring children with chronic spontaneous urticaria during the COVID-19 pandemic, revealing that both SARS-CoV-2 infection and vaccination may trigger relapses or worsening of the condition.
DOI: 10.15586/aei.v50iSP2.722 -
Increased Risk of Urticaria/Angioedema after BNT162b2 mRNA COVID-19 Vaccine in Health Care Workers Taking ACE Inhibitors
This study evaluates the increased risk of urticaria and angioedema following the BNT162b2 mRNA COVID-19 vaccine in healthcare workers taking ACE inhibitors, finding a three-fold increased risk in this population.
DOI: 10.3390/vaccines9091011 -
Varicella Zoster Reactivation Following mRNA Vaccination: Two Case Reports and a Review of Cutaneous Adverse Events of COVID-19 Vaccines
Two case reports describe varicella zoster reactivation after Pfizer-BioNTech mRNA COVID-19 vaccination in an 80-year-old woman and a 57-year-old man, with a review of cutaneous adverse events.
DOI: 10.33590/emj/21-00254 -
Stress, pseudoallergens, autoimmunity, infection and inflammation in chronic spontaneous urticaria
A comprehensive narrative review arguing that chronic spontaneous urticaria (CSU) arises from multifactorial interactions among autoimmunity, pseudoallergens, stress, infection, gut dysbiosis, and coagulation, and advocating a holistic management approach that targets these inte…
DOI: 10.1186/s13223-019-0372-z -
In chronic spontaneous urticaria, IgE against staphylococcal enterotoxins is common and functional
IgE antibodies to Staphylococcus aureus enterotoxins are common in chronic spontaneous urticaria (CSU), especially SEB, and SEB-IgE is functionally active—correlating with total IgE and disease activity and capable of triggering basophil histamine release—suggesting a contributo…
DOI: 10.1111/all.13381