Flu vaccine associated with small increased risk for subdeltoid bursitis

Influenza vaccination was associated with a small risk for subdetltoid bursitis in a large retrospective cohort study, an association that was previously supported by clinical evidence from case reports. Education and training on proper injection technique could prevent this adverse event. Findings are published in Annals of Internal Medicine.

Subdeltoid bursitis, characterized by pain and loss of motion in the shoulder, occurs in about 1 percent of the U.S. population and is usually due to injury. In 2012, an Institute of Medicine report concluded that evidence supported a causal relationship between the injection of a vaccine and deltoid bursitis, however, epidemiologic evidence for this relationship was lacking.

Researchers from the Centers for Disease Control and Prevention (CDC) studied data from the Vaccine Safety Datalink, which contains health encounter data for 10.2 million members of 7 U.S. health care organizations, to estimate the risk for subdeltoid bursitis after influenza vaccination. Of 2, 943, 493 vaccinated persons included in the analysis, the researchers found 16 cases of symptom onset in the risk interval and 51 cases of symptom onset in the control interval. The attributable risk was 7.78 additional cases of bursitis per 1 million persons vaccinated.

The authors of an accompanying editorial from Emory University School of Medicine and the University of Pennsylvania point out that vaccination technique seems to be a common theme in this study as well as in previous studies. Both needle placement and needle length matter. Hence, a technique "tune-up" could help to eliminate this adverse reaction among persons having vaccinations.