Viral RNA in the influenza vaccine may have contributed to the development of ANCA-associated vasculitis in a patient following immunisation.

A number of large studies have demonstrated influenza vaccinations to be safe and effective. However, there have been some sporadic case reports, describing a temporal association of influenza vaccination with onset or relapse of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis. The nature of this association, beyond time of occurrence, remains unknown. The presentation of a previously healthy patient who developed ANCA-associated vasculitis (AAV) shortly after influenza vaccination provided us with the rare opportunity to study the possible mechanisms behind this observation. We tested the ability of different types and batches of influenza vaccines to stimulate proteinase-3 ANCA (PR3-ANCA) production in vitro. We found that only some influenza vaccines stimulated PR3-ANCA production in this patient. We demonstrated that this unusual response was associated with those vaccines that contained viral ribonucleic acid (RNA), the natural ligand for Toll-like receptor-7. Exome sequencing of the patient's DNA did not show any mutation in any of the molecules associated with Toll-like receptor signalling. We propose that hyper-reaction to viral RNA in the influenza vaccine may have contributed to the development of AAV following influenza vaccination in this patient.