Atraumatic osteonecrosis of the humeral head after influenza A-(H1N1) v-2009 vaccination

In the recent pandemic influenza A-(H1N1) v-2009 vaccination campaign, adjuvanted vaccines have been used because of their antigen-sparing effect. According to available reports, the rate of severe vaccination reactions has not increased, as compared with previous seasonal influenza vaccinations. Here we describe an adult female patient who was vaccinated with an AS03 adjuvanted split-virus vaccine injected into the left arm. She experienced a prolonged and painful local reaction for 4 weeks. During this time, persistent incapacitating pain shifted into the left shoulder. Magnetic resonance imaging (MRI) at the injection site detected atraumatic humeral head osteonecrosis in conjunction with bursitis of the rotator cuff region. Clinical and laboratory examination revealed no other underlying disease. Using analgetic medication and physical therapy, resting pain completely remitted within the following 14 weeks. Pain on exertion declined within the following 6 months. Atraumatic osteonecrosis, a relatively rare disorder which initially presents non-specific clinical symptoms, has never been associated with parenteral influenza vaccination. Although the available data cannot establish a causal relationship, our patient's clinical course - with a continuous transition from increased local post-vaccination reactions to symptoms of a severe shoulder lesion with osteonecrosis - raises the question of a pathogenetic link. Considering the vascular pathogenesis of osteonecrosis, we hypothesize that our patient's enhanced local immunologic reaction may have led to regional vasculitis as the cause of bone destruction. As mild forms of osteonecrosis may have escaped previous clinical attention, it is the purpose of our report to increase awareness of this exceptional event as a possible side effect of parenteral adjuvanted vaccination.