Moderate biceps tenosynovitis; Shoulder injury related to vaccine administration; Larger than recommended 20-gauge, 1.5-inch needle was used; Concerned that the vaccination placement was 'too high in my shoulder'; This is a literature case, initially received from other health professional on 30-Sep-2019, concerning a 35-year-old, female patient.   A 35-year-old female, full-time health care worker at a 244-bed hospital, weighing 135 pounds, with no significant past medical or surgical history, presented to the hospital employee health service (EHS) approximately 1 hour after receiving unspecified Flu Vaccine [Influenza virus vaccine polyvalent, anatomical location: left upper arm, route of administration, dose, batch number and expiration date: not reported] to promote large scale immunization in the hospital workforce.   Immediately after the vaccine administration, the health care worker felt pressure and intense pain in the left shoulder, localized to its anterior aspect. In a numerical pain rating scale, with 0 representing "no pain at all" and 10 representing "the worst pain ever possible," in this case, pain was self-rated as 10 out of 10. By 1 hour, this evolved to stiffness and difficulty moving the left arm at the shoulder. At self-referral to the EHS, pain was described as "achy." The health care worker had received an annual influenza vaccination over 10 years of employment without previously experiencing similar symptoms. The health care worker recalled that the vaccination had been administered by a nurse using a 20-gauge, 1.5-inch needle and was concerned that the vaccination placement was "too high in my shoulder''. Any coincident recent shoulder trauma, excessive pulling, lifting overhead, or leisure activities (e.g., racquet sports, swimming) were denied by the worker.  Upon inspection by an occupational medicine physician, there was no visible bruising, erythema, or swelling noted on the left shoulder. Pain was exacerbated by shoulder manipulation, most notably with abduction and flexion. Active range of motion was limited to 45 degrees with forward flexion and extension. Reflexes, strength, and sensation were intact. A magnetic resonance imaging (MRI) without contrast was performed within 1 week of injury and demonstrated a moderate glenohumeral joint effusion and synovitis, with fluid accumulating in the subscapularis recess, in addition to changes consistent with a moderate biceps' tenosynovitis. The health care worker was treated conservatively with nonsteroidal anti-inflammatory medication (Ibuprofen) and 5% lidocaine patch, placed on modified work duty, prescribed physical therapy, and referred for orthopedic specialist consultation, and to our knowledge, she has been adherent to this plan.  Over the next several weeks, the health care worker came in for regular weekly follow-up visits at the EHS, where she was seen by an occupational medicine trainee, with input from an occupational health nurse practitioner and a second occupational medicine physician. The patient reported ongoing (4 out of 10) dull pain at rest, sleep disturbance due to pain, and difficulty lifting, carrying, and especially driving. On physical examination 4 weeks after the injury, left deltoid pain was still appreciable with restricted abduction (45 degrees) as well as pain upon passive abduction and flexion. Findings by the physical therapist were also consistent with the observed limited range of motion. The health care worker continued to be on modified duty and use nonsteroidal pain medication. Six weeks after the injury, the health care worker had completed six sessions of physical therapy with substantially improved range of motion, although not yet to baseline, and a pain level was rated as 3 out of 10. At that time, a second MRI demonstrated near-complete resolution of the glenohumeral joint effusion but changes consistent with tenosynovitis of the extraarticular portion of the biceps' tendon remained. A third MRI was performed 8 months after initial date of injury, showing persistent mild tenosynovitis of the long head of the biceps tendon, interval accumulation of a large glenohumeral joint effusion, and infraspinatus tendinitis with subjacent reactive bone marrow edema. The health care worker remained on modified duty (no overhead reaching on the left, no lifting or pushing with the left arm) and continued to receive physical therapy for at least 8 months since the initial injury with ongoing limitation to the left shoulder range of motion and persistent shoulder pain (3 out of 10). The health care utilization associated with managing this worker's injury included multiple physical therapy sessions, consultations with specialty providers, pharmacologic therapies, and several imaging studies. The affected employee experiences ongoing work restrictions but, to date, has had no complete lost workdays due to the injury.  Discussion: This case of SIRVA illustrates its associated morbidity in an occupational setting. Although there were no lost workdays and we do not have access to the health care related charges or costs in this case, there was considerable utilization of resources and an ongoing work restriction. Tenosynovitis and joint effusions occur in approximately 70% to 80% of SIRVA cases and bone marrow edema in 30% to 50% of cases, which is consistent with the findings of our case. Shoulder symptoms related to SIRVA can persist from 6 months to years. The case continued under the care of an orthopedic specialist and physical therapist exceeding 6 months of ongoing treatment.  Contributing Factors: This preventable injury and its subsequent sequalae can result from any one or multiple of the following factors: (a) inadequate training of the vaccine administering clinical staff; (b) use of an inappropriately sized needle (gauge and length); (c) deficits in knowledge of anatomical structures, leading to poor selection of the injection site; and (d) failure by health care providers to recognize the symptoms of vaccine misadministration. Lack of immediate referral for medical follow-up may contribute to resultant morbidity. The CDC has developed specific guidelines focused on training and educating health care staff administering vaccines and recommends that a 1-inch, 22- to 25-gauge needle be used for both men and women weighing 130-152 pounds when administering influenza vaccine (CDC, 2019). In this specific case, the level of training provided to the health care staff who administered the influenza vaccine was unclear and a larger than recommended 20-gauge, 1.5-inch needle was used. A diagnosis of SIRVA is suspected when the person who has been vaccinated experiences shoulder pain and decreased range of motion within 48 hours of receiving a "very high" deltoid injection. Most often, the shoulder pain does not respond to a trial of nonsteroidal anti-inflammatory drugs and may require corticosteroid injections into the shoulder. Of note, plain radiographs are often unrevealing. Ultrasound examination or, as in this case, MRI may reveal effusion and changes consistent with tendonitis. The most common vaccines associated with SIRVA are the seasonal influenza and tetanus immunization. This is likely because these vaccines are most commonly administered to adults. Regarding health care workers, the annual influenza vaccination has been shown to reduce morbidity and mortality, work absence, and infection transmission to patients.; Sender's Comments: The patient developed tenosynovitis and shoulder injury related to vaccine administration after vaccination with the suspect product, INN Flu Vaccine. Chronology seems plausible. Reportedly, the health care worker recalled that the vaccination had been administered by a nurse using a 20-gauge, 1.5-inch needle and was concerned that the vaccination placement was "too high in my shoulder", suggesting wrong technique in product usage process and that the product was administered at inappropriate site. There is a lack of information provided regarding patient's medical history. Causal relationship between the suspect product and the events of wrong technique in product usage process and product administered at inappropriate site is assessed as not related based on company's conventions, while for other two events is assessed as possibly related.