Yellow fever vaccine in egg-allergic patients: safety of a vaccination protocol

Abstract

Yellow fever vaccine (YFV) is broadly recommended in endemic areas, considering the severity of this disease. However, the vaccine is grown in chicken embryos and poses a risk to egg allergic (EA) patients. We describe the outcomes of a protocol for administration of YFV in EA patients. Five EA children were included, two of them anaphylactic. Patients older than 5 years were skin tested with the vaccine (prick and intradermal). Skin test-negative patients received the vaccine as a single dose under a physician’s supervision. Skin test-positive patients underwent a desensitization protocol: 0.05 ml of a 1:10 dilution, followed by graded full strength doses: 0.05 ml, 0.1 ml, 0.15 ml, 0.2 ml at 15-minutes intervals, totaling 0.5mL. Younger children were not tested and followed the desensitization protocol. Premedication was not administered. Two patients (1 and 4 years old) were too young to be skin tested. The other three (5, 7, and 9 years old) underwent skin tests. All prick tests were negative and two patients had positive intradermal tests. The patient with negative tests received the vaccine as a single dose without adverse reactions. Four patients received the vaccine through the desensitization protocol. Three of them didn’t experience any symptoms and one toddler presented hives after receiving the second dose. She was treated with antihistamines and was able to finish the protocol without further reactions. In this case series a desensitization protocol proved to be safe and efficient in allowing vaccination of EA patients (including severe phenotypes) against yellow fever.