got the flu shot in my right arm; it is very swollen like cellulitis; joints aching/ knee; Initial information received on 29-Aug-2023 regarding an unsolicited valid non-serious case received from a patient via specialty pharmacy.  This case involves a 68 years old female patient who had joints aching/ knee and got the flu shot in my right arm; it is very swollen like cellulitis while receiving vaccine INFLUENZA VACCINE and while treated with DUPILUMAB [DUPIXENT] delivered via single dose prefilled pen.  The patient's past medical history included Unspecified nasal polyp. The patient's past medical treatment(s), vaccination(s) and family history were not provided. At the time of the event, the patient had ongoing drug allergies: codeine sulfate, d.farinae mite extract, gnp glucosamine chondroitin tb (tablet), non-drug allergies: elm (allergy to plants), adhesive tape, latex  Concomitant medications included PARACETAMOL (TYLENOL); IBUPROFEN (MOTRIN IB); THYROID (ARMOUR THYROID); CALCIUM CARBONATE, COLECALCIFEROL, CUPRIC OXIDE, MAGNESIUM OXIDE, MANGANESE SULFATE, SODIUM BORATE, ZINC OXIDE (CALCIUM 600 + D3 PLUS MINERALS); ARIPIPRAZOLE (ABILIFY); VENLAFAXINE HYDROCHLORIDE (EFFEXOR); SALBUTAMOL SULFATE (ALBUTEROL SULFATE HFA); ESCITALOPRAM OXALATE (LEXAPRO); MONTELUKAST SODIUM (SINGULAIR); METOPROLOL SUCCINATE (METOPROLOL SUCCINATE); LISINOPRIL (LISINOPRIL); BUDESONIDE (PULMICORT); FLUTICASONE PROPIONATE, SALMETEROL XINAFOATE (ADVAIR); FLUTICASONE PROPIONATE (FLONASE ALLERGY RELIEF); FEXOFENADINE HYDROCHLORIDE (ALLEGRA ALLERGY); COLECALCIFEROL (VITAMIN D3); ASCORBIC ACID (VITAMIN C [ASCORBIC ACID]); and CALCIUM, MINERALS NOS (CALCIUM;MINERALS NOS).  On 06-Mar-2023, the patient started taking DUPIXENT (DUPILUMAB) Solution for injection at a dose of 300 mg (every other week) QOW via subcutaneous route (strength: 300 mg/2 ml) (with unknown batch number, expiry date) for moderate or severe asthma and nasal polyp unspecified delivered via single dose prefilled pen. Information on batch number and expiry date requested.  On an unknown date, the patient received an unknown dose of suspect INFLUENZA VACCINE produced by unknown manufacturer (batch/lot number, formulation, route, strength, expiry date not reported) in unknown administration site for prophylactic vaccination (immunization).  In JUN-2023 the patient developed a non-serious event "joints aching/ knee" (arthralgia) (approximate 3 months latency) following the first dose intake of DUPILUMAB and following the administration of INFLUENZA VACCINE.  On 14-SEP-2023 the patient developed a non-serious event "got the flu shot in my right arm; it is very swollen like cellulitis" (peripheral swelling) (Latency: 6 months 8 days) following the first dose intake and (unknown latency) following the last dose intake of DUPILUMAB and following the administration of INFLUENZA VACCINE.  It was reported "the patient reports, joints aching in the "past couple months, per patient her primary care provider administered a cortisone injection in her knee. the patient reports it was caused by the weather and it went away a couple days later. Patient reported that she got the flu shot in her right arm last thursday and it was very swollen like cellulitis. She wanted to know if that has to do with she being on dupixent No additional information was provided"  Action taken with DUPILUMAB (DUPIXENT) was unknown for both the events and not applicable with INFLUENZA VACCINE for both the events.  Corrective treatment: The patient was treated with CORTISONE (CORTISONE) for Arthralgia. Not reported for other event.  At time of reporting, the outcome was Recovered / Resolved in July 2023 for the event joints aching/ knee and was Unknown for the event got the flu shot in my right arm; it is very swollen like cellulitis.  Additional information was received on 18-Sep-2023 from patient: Event (peripheral swelling) added, suspect added, concomitant added, clinical course updated and text amended accordingly.