A new study has determined that adult patients in Italy with hereditary angioedema (HAE) with C1 esterase inhibitor deficiency (C1-INH) can be safely vaccinated against COVID-19.

The study, published in Vaccines, found no increase in monthly attack rates or severe adverse reactions following the vaccination.

Previous studies conducted in relatively small populations of patients with HAE reported that about 10–15% of patients developed angioedema attacks shortly after the injection of COVID-19 vaccines,” the authors wrote. “Hence, we performed a multicentric retrospective observational study in order to evaluate the angioedema attack rate and the occurrence of adverse reactions following the vaccination in patients affected by HAE and acquired angioedema due to C1 inhibitor deficiency in Italy.”

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The research team assessed a cohort of 208 adults with HAE-C1-INH or acquired angioedema (AAE)-C1-INH at Italian medical centers. The primary outcome measure of the study was the safety and tolerability of the COVID-19 vaccine in terms of angioedema attack rates and adverse reactions within 72 hours of the vaccine. Secondary measures included predictive factors of attacks following vaccination and changes in attack frequency over 6 months following the vaccination.

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The results revealed that 7.4% of the cohort experienced exacerbated attacks following the initial vaccination, which represented no significant increase compared with similar studies. Furthermore, the attacks that occurred were not more severe than those prior to the vaccination. However, there was an increase in the attack rate to 14.5% following the 3rd immunization.

No hospitalizations occurred due to the SARS-CoV-2 vaccination in this cohort. The most common adverse reaction was pain at the injection site and there was a higher rate of fever among patients in this cohort compared with other studies.

The authors conclude that vaccination against COVID-19 and the booster doses are generally safe and well tolerated among patients with HAE and AAE and are recommended.


Parente R, Sartorio S, Brussino L, et al. Multicentric observational study on safety and tolerability of COVID-19 vaccines in patients with angioedema with C1 inhibitor deficiency: data from Italian Network on Hereditary and Acquired Angioedema (ITACA). Vaccines. Published online April 16, 2023. doi:10.3390/vaccines11040852