Abstract
As more individuals receive outer surface protein A (OspA) vaccination, adverse effects not detected during phase III clinical trials may become apparent. Although arthritis has been described following other human vaccines, we found no reports of human cases after Lyme disease vaccination. We describe 4 males (2 children, 2 adults) who developed arthritis following recombinant OspA vaccination. The potential arthritogenic effect of OspA suggested by in vitro and animal studies finds a clinical correlate in these 4 cases.