Prolonged febrile illness following first dose of ChAdOx1.

A woman in her 40s, with a known history of fibromyalgia, presented with high-grade fever and constitutional symptoms occurring 5 days following vaccination with Oxford-AstraZeneca COVID-19 vaccine (ChAdOx1). Her inflammatory markers and neutrophil count were found to be elevated and as such, she was started on antibiotics. Despite treatment, markers remained elevated and temperature spikes persisted for another 4 weeks before these symptoms subsided, and her blood tests normalised. All investigations taken in the interim were negative, with no source being identified for the fever. As a result, a positron emission tomography scan was performed to attempt to localise the source of these symptoms. This revealed low-to-moderate grade lymph node tracer uptake above and below the diaphragm most pervasive in the right axilla, with uptake in the right arm corresponding with the site of vaccination.