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Immunization Stress-Related Responses (ISRRs) are more common than hypersensitivity reactions after mRNA COVID-19 vaccination

Published: August 8, 2022

Immediate hypersensitivity reactions (IHSRs) and immunization stress-related responses (ISRRs) are common adverse events following immunization. Information regarding incidence rate and risk factors for such reactions is crucial for clinicians working in coronavirus disease-2019 (COVID-19) mass vaccination centers. A majority of existing reports are focused on severe adverse events, such as anaphylaxis or vasovagal syncope, whereas information on the incidence rate and risk factors associated with non-severe IHSR and ISRR is limited despite its importance in establishing a safe mass vaccination system.

In a research article recently published in The Journal of Allergy and Clinical Immunology: In Practice, Dr. Imai, Dr. Mizuguchi, and their colleagues investigated the incidence rate and risk factors associated with IHSR and ISRR after COVID-19 vaccination at a mass vaccination center in Japan.

A total of 1,201,688 vaccine doses (611,779 and 589,909 shots for first and second vaccine dose, respectively) were administered to 614,151 vaccine recipients at the study center. The study estimated the incidence rate of adverse event per million doses of vaccine: IHSR, 266 cases; ISRR, 2,129 cases; anaphylaxis, 2 cases; and vasovagal syncope, 72 cases. Among the vaccine recipients with IHSR after the first dose, only 7% developed recurrent IHSR after the second dose; however, none of the recipients were diagnosed with anaphylaxis. They identified that female gender, asthma, atopic dermatitis, thyroid diseases, and drug and food allergy histories were associated with an increased risk of IHSR. On the other hand, younger age, female gender, asthma, mental disorders, drug and food allergy histories, and vasovagal reflex history were associated with an increased risk of ISRR. The most common symptoms of ISRR were vertigo, malaise and numbness.

This study highlighted the low incidence rate of IHSR and anaphylaxis associated with Moderna COVID-19 vaccine suggesting that it can be safely used for mass vaccinations. However, healthcare providers need to take appropriate measures to prevent and adequately respond to ISRR development, which has a higher incidence rate than IHSR. Vaccine recipients have a slightly increased risk for IHSR and ISRR but this is not of sufficient magnitude to warrant a contraindication to vaccinations or adoption of any special measures.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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