Safety of COVID-19 revaccination in patients with prior hypersensitivity reactions: a retrospective study.

Background: Hypersensitivity reactions (HSR) to the COVID-19 vaccine have been reported. Despite these reactions, revaccination remains essential.

Objective: This study aims to explore the potential outcomes of COVID-19 revaccination in individuals with prior vaccine-related adverse reactions.

Methods: A retrospective study was employed with a sample of 225 patients, with HSR regarding COVID-19 vaccines, who were referred to a university hospital. Demographic data, vaccine types and HSR were collected.

Results: Seventy-seven percent (175/225) of patients were revaccinated post HSR. Out of the 175 patients, 57.1%, 34.2% and 8.5% had a history of HSR in connection to inactivated vaccines, viral vector vaccines, and mRNA vaccines, respectively. Sixty percent were revaccinated with the same type of vaccine and 63.4% received antihistamines and/or anti-leukotriene premedication. After revaccination, 89.1% did not have adverse reactions, while 10.9% had mild reactions. When comparing patients who experienced HSR following COVID-19 revaccination with those who did not exhibit reactions, a significant association among patients with revaccination adverse effects were a revaccination with inactivated vaccines; Sinovac-CoronaVac (P < 0.001), a history of any allergic diseases (P < 0.001) and underlying allergic rhinitis (P = 0.003). Premedication or change of vaccine type did not have an effect to the rate of adverse reactions reported post revaccinations.

Conclusions: In this study, COVID-19 revaccination in patients with a history of COVID-19 vaccine-related HSRs was generally safe, with most patients tolerating it well. However, individuals with underlying allergic conditions, particularly allergic rhinitis, exhibited a higher incidence of mild reactions, especially following revaccination with an inactivated vaccine.