Study shows small risk for bursitis after influenza vaccination
A small risk for subdeltoid bursitis was observed among nearly 3 million patients who received an influenza vaccination in the United States, according to a retrospective population-based cohort study.
An increasing number of reports — including a 20-fold increase in the number of claims for shoulder-related adverse events submitted to the National Vaccine Injury Compensation Program from 2012 to 2016 — imply a causal relationship between the injection of a vaccine and subdeltoid bursitis, Elisabeth Hesse, MTM&H, MD, epidemic intelligence service officer at the CDC, and colleagues wrote in Annals of Internal Medicine.
“Our objective was to enhance the rigor of epidemiologic evidence by estimating the risk for subdeltoid bursitis after influenza vaccination,” they wrote.
Hesse and colleagues studied data from 2.943 million influenza vaccinations administered at seven sites in the United States from Sept. 1, 2016, through June 1, 2017. The vaccine recipients were at least 3 years of age. Most were between 18 and 49 years old, female, and received a standard-dose inactivated influenza vaccine trivalent. Hesse and colleagues also performed a self-controlled risk interval analysis to determine the incidence rate ratio of subdeltoid bursitis during a risk interval of 0 to 2 days after vaccination vs. a control interval of 30 to 60 days after vaccination.
The researchers identified 257 cases of subdeltoid bursitis. Among them, 16 had symptom onset in the risk interval, 51 had symptom onset in the control interval and 190 had symptom onset in neither prespecified interval. The median age of persons in the risk interval was 57.5 years and 69% were women. The incidence rate ratio was 3.24 (95% CI, 1.85–5.68) and the attributable risk was 7.78 (95% CI, 2.19–13.38) additional cases of bursitis for each 1 million persons vaccinated.
According to the researchers, two case patients who developed subdeltoid bursitis reported potential vaccination administration errors. However, the researchers were unable to establish this link.
“Strategies to prevent [subdeltoid bursitis], which may include improved education and training about proper vaccination technique, need to be identified and implemented,” Hesse and colleagues wrote.
In a related editorial, Sandra Adamson Fryhofer, MD, MACP, FRCP, adjunct associate professor of medicine at Emory University School of Medicine in Atlanta, and George W. Fryhofer, MD, MTR, an orthopedic resident at the University of Pennsylvania, built on Hesse and colleagues’ observation by providing an “injection technique tune-up.”
“First, regarding [needle] placement — know your anatomical landmarks,” they wrote. “Aim for the midpoint of the deltoid muscle, 2 to 3 fingers' width below the acromion process (and above the armpit). Inject at a 90° angle. No aspiration is needed.”
Correct needle length depends on weight and sex. The object is to inject into the muscle, not through it, which can put the bursa at risk.”
According to the Fryhofers, the CDC recommends needle lengths of five-eighths of an inch for persons weighing less than 60 kg; 1 inch for persons weighing 60 kg to 70 kg; and 1 inch to 1.5 inches for women weighing more than 90 kg and men weighing more than 118 kg.
The authors recommended that physicians weigh Hesse and colleagues’ findings in the context of CDC data that suggest the influenza vaccine prevented more than 5.2 million illnesses, 2.6 million medical encounters, 72,000 hospitalizations and 5,000 deaths during the 2016-2017 influenza season.
“Bottom line — keep vaccinating!” the Fryhofers concluded.
- Fryhofer SA, et al. Ann Intern Med. 2020;doi:10.7326/M20-3302.
- Hesse EM, et al. Ann Intern Med. 2020;doi:10.7326/M19-2176.