Cellulitis; The vaccine was given incorrectly (too low); This spontaneous case was received on 28-Sep-2020 from a pharmacist (reference number: SEQW20-02481) and concerned a female patient of unknown age.  The patient's concurrent condition included diabetes. The patient's concomitant medications included metformin for unreported indication.   On 15-Sep-2020, the patient was vaccinated with Fluad Quadrivalent (influenza vaccine, inactivated influenza virus surface antigen (subunit), egg-derived, mf59l; dose: 0.5 ml, anatomical location: left deltoid, indication, route of administration: not reported). The batch number reported was 279791, expiry date: 28-May-2021.   On 16-Sep-2020, one day after receiving Fluad Quadrivalent, the patient developed pain, redness, swelling and itching.  On an unknown date in Sep-2020, the patient came by the pharmacy and was advised to use unspecified cream. The patient was seen by her physician and was diagnosed with cellulitis. The patient's physician felt the vaccine was given incorrectly (too low) and this caused the cellulitis (explicitly coded as 'Vaccine administered at inappropriate site'). The physician prescribed Bactrim (sulfamethoxazole, trimethoprim) as treatment. The patient had an upset stomach due to Bactrim, as reported. The pharmacy was not able to see the injection site again to verify that the vaccine was given too low.  On an unknown date in Sep-2020, redness, swelling and itching had resolved and the patient recovered from the event.   The reporter did not provide a causality assessment. The patient's physician felt the vaccine was given incorrectly (too low) and this caused the cellulitis.   The event of cellulitis was considered to be medically significant by a Physician.  Company comment: A female patient of unknown age developed cellulitis, one day after receiving Fluad Quadrivalent vaccine. Chronology is plausible. Reportedly, the patient developed pain, redness, swelling and itching which was diagnosed as cellulitis. The patient's physician felt the vaccine was given incorrectly (too low) and this caused the cellulitis (explicitly coded as 'Vaccine administered at inappropriate site'). The physician prescribed Bactrim (sulfamethoxazole, trimethoprim) as treatment. With information available, causal role of the suspect vaccine is assessed as possibly related. Although from the report seems that events were at vaccination site, it was not clear and therefore the case does not meet BC definition of cellulitis at injection site. Vaccine administered at inappropriate site is not related to the suspect vaccine per company's conventions.; Reporter's Comments: The patient's physician felt the vaccine was given incorrectly (too low) and this caused the cellulitis.; Sender's Comments: A female patient of unknown age developed cellulitis, one day after receiving Fluad Quadrivalent vaccine. Chronology is plausible. Reportedly, the patient developed pain, redness, swelling and itching which was diagnosed as cellulitis. The patient's physician felt the vaccine was given incorrectly (too low) and this caused the cellulitis (explicitly coded as 'Vaccine administered at inappropriate site'). The physician prescribed Bactrim (sulfamethoxazole, trimethoprim) as treatment. With information available, causal role of the suspect vaccine is assessed as possibly related. Although from the report seems that events were at vaccination site, it was not clear and therefore the case does not meet BC definition of cellulitis at injection site. Vaccine administered at inappropriate site is not related to the suspect vaccine per company's conventions.