There is a small absolute risk for shoulder conditions after vaccination administered in the deltoid muscle, according to a study published in Annals of Internal Medicine. Chengyi Zheng, PhD, and colleagues conducted a retrospective cohort study to identify shoulder conditions among vaccinated persons with discharge codes for shoulder disorder. Participants were aged 3 or older and had a vaccine administered in the deltoid muscle between April 2016 and December 2017. The researchers identified 371 shoulder conditions among approximately 3.8 million administered vaccinations, with an estimated incidence of 0.99 per 10,000 vaccinations. For the adult (≥18) and pediatric (3-17) populations, the incidence rates were 1.22 and 0.05, respectively, per 10,000 vaccinations. Among adults, risk for shoulder conditions increased in association with advanced age, female sex, more outpatient visits in the 6 months before vaccination, lower Charlson Comorbidity Index, and pneumococcal conjugate vaccine. With influenza vaccines, risk for shoulder conditions was increased with quadrivalent vaccination. For elderly persons, simultaneous administration of vaccines was associated with a higher risk for shoulder conditions.
