This is a serious literature case, initially received on 11-Feb-2019, concerning a 61-year-old, adult,  female patient. The patient's historical condition included myocardial infarction. The current condition included hypertension. The patient denied any recent and past injury to her shoulder, fever, chills, rash, or skin changes at the injection site. The concomitant medications included lisinopril, atenolol and aspirin (acetylsalicylic acid). On an unspecified date, the patient was administered INN Flu Vaccine Seasonal (influenza vaccine, influenza virus vaccine polyvalent, anatomical location: right arm, dose, route of administration, batch number, manufacturer, trade name and expiry date: not reported) for an unknown indication. On an unspecified date, the patient presented with acute right shoulder pain that began after she received an influenza vaccination at a local pharmacy 2 weeks earlier. The patient pointed to the proximal-most aspect of her lateral right upper arm as the vaccination site. The pain intensified with shoulder abduction, forward flexion, and reaching movements. The patient had continued to participate in her aerobics class, despite the discomfort. On an unspecified date, the physical exam report described the patient as a thin female with no visible rashes or erythema on her right shoulder. While there was no deltoid atrophy in comparison to the unaffected shoulder, the patient generally had low muscle mass in both arms. A painful arc of abduction was present, as was pain with palpation of the supraspinatus insertion. No pain was appreciated over the short or long head of the biceps tendon or the sternoclavicular or acromioclavicular joints. Strength was 5/5 for all movements of the rotator cuff, but pain was reproduced with resisted shoulder abduction. On an unspecified date, Hawkin's test was performed and the result was positive. On unspecified date, Speed's, Yergason's, cross-arm abduction and O'Brien's tests were performed, and the result were negative. On an unspecified date, anteroposterior, Grashey, Y-view, and axillary view radiographs of the right shoulder were normal without any calcific tendinopathy, degenerative changes, or acute fractures. The patient was diagnosed with rotator cuff tendinitis. The patient was provided with treatment options, which included physical therapy and nonsteroidal anti-inflammatory drugs (NSAIDs), but the patient elected to go forward with a corticosteroid injection. So, the patient was administered 2 cc of Depo-Medrol 40 mg/mL with 2 cc of 1 percent lidocaine (lidocaine hydrochloride, methylprednisolone acetate) without epinephrine and 2 cc of 0.5 percent ropivacaine into her right shoulder subacromial space using a posterior approach. Immediately following the treatment, the patient noticed a 70 percent improvement in her pain. At the patient's 2-month follow up, there was overall 80 percent improvement in pain (recovering). The patient had occasional discomfort with certain movements, although the pain was relieved with over-the-counter anti-inflammatory medication. On physical exam, the patient had an intact arc of abduction of the right shoulder to 150 degree without pain. Forward flexion and external and internal rotation were normal and pain free. The patient had mild pain with resisted abduction and a positive Hawkin's test. The patient agreed to go to physical therapy to work on rotator cuff strengthening. The patient denied any known influenza infection up to that time. The outcome of the events rotator cuff tendinitis, shoulder pain, pain upon movement, tenderness was recovering, and outcome of the event discomfort was not recovered. The reporter concluded that rotator cuff tendinitis in the patient was a secondary to an immune response to an influenza vaccination that infiltrated the supraspinatus tendon (causality: related).; Reporter's Comments: A 61-year-old, female patient experienced acute right shoulder pain, within 2 weeks after administration of INN Flu Vaccine. The pain intensified with shoulder abduction, forward flexion, and reaching movements and was eventually diagnosed as rotator cuff tendinitis. Considering the plausible temporal relationship between vaccination and reported events, plausible biological mechanism, site-specific nature (injection arm) and lack of any underlying conditions or alternative more plausible causes, the company assessed the events as possibly related to suspect vaccine.The company assessed the case as serious (medically signnficant).