Safety of yellow fever vaccine administration in confirmed egg-allergic patients

Abstract

The yellow fever vaccine (YFV) is recommended in endemic areas but represents a risk for egg-allergic patients, as it is cultivated in chicken embryos. This study aims to describe the outcomes of yellow fever vaccination in patients with confirmed egg allergy (EA). Prospective study in a quaternary hospital, from January 2018 to September 2019. EA was diagnosed through oral food challenge (OFC) or recent history of anaphylaxis following egg contact (anaphylaxis in the last 6 months) or allergic reaction in the last 2 months with positive specific IgE. Skin prick test (SPT) with YFV was performed in all participants. If negative SPT, an intradermal test (ID) was performed at 1:100 dilution. If negative ID, a full dose of YFV was administered. If positive skin test, the YFV was administered using a graded-dose protocol. Among 100 patients with prior EA history, 58 were confirmed (36M:22F), median age of 2.35y (0,7 a 13,9Y). Forty-two patients had a positive OFC. Nine reported recent anaphylaxis. The other 7 had reaction in the last 2 months with positive specific IgE. During OFC, 15 presented anaphylaxis and the other (27) presented urticaria and/or angioedema or vomiting. SPT with YFV was negative in all patients. ID was negative in 48 patients, who received a full dose of YFV in usual manner, uneventfully. Ten patients had a positive ID and received the YFV in graded doses, six of them presented a mild reaction controlled with antihistamines and four patients received the vaccine without reactions. Positive ID was significantly related to vaccine reaction (p=0,0001). Administration of YFV using a specific protocol was safe even in anaphylactic patients. We only recommend performing the ID test which contributed to predicting a higher risk of vaccine reaction. An appropriate setting is required in order to control adverse events.