Bursitis has many causes, including autoimmune disorders, crystal deposition (gout and pseudogout), infectious diseases, traumatic events, and hemorrhagic disorders, as well as being secondary to overuse. Repetitive injury within the bursa results in local vasodilation and increased vascular permeability, which stimulates the inflammatory cascade. Subdeltoid and subacromial bursitis have been reported after vaccination when poor technique results in direct injection of the vaccine into the bursa.