Clinical Investigation on Allergic-like Reactions and Oculo-respiratory Syndrome After the H1N1 Pandemic Vaccine

Plain-language summary

During the 2009-2010 immunization campaign against pandemic H1N1, some people reported having allergic-like reactions (anaphylaxis(a shock-like reaction), hives, swelling, etc.). A vaccine allergy may be more or less severe or intense. Patients may have skin reactions (rash with or without itching), respiratory problems (cough, spasm of the airways), angioedema (swelling) of various body parts (face, eyelids, throat etc.) and circulatory problems (low blood pressure or shock). Anaphylaxis is a severe allergic reaction that can sometimes be fatal. Other people vaccinated against pandemic H1N1 had an oculo-respiratory syndrome. Oculo-respiratory syndrome (ORS) is also a reaction to the influenza vaccine, which includes symptoms such as bilateral conjunctivitis (red eyes) with swelling of the face or respiratory symptoms (chest tightness, coughing, a sensation of throat closure, difficulty swallowing, hoarseness, wheezing or difficulty breathing). The investigators know that ORS is not a true allergic reaction. Because many signs and symptoms of ORS are similar to those observed during an allergic reaction, it is often difficult to distinguish ORS from an allergic reaction. This study will compare three groups of patients: those who had allergic-like reactions, those who had ORS and vaccinated individuals who had no such adverse events. Pregnant women cannot participate in this study. The study has three goals. First, the investigators want to determine, among those who had allergic-like reactions after influenza vaccination, what proportion (percentage) of these people are actually allergic to the vaccine or its components. Second, among those who are not allergic to the vaccine, which other processes may have caused these symptoms. Finally, the investigators will try to identify whether there are features that distinguish patients who have a true allergic reaction from those affected by ORS, and those that had no adverse events.

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Trial details