Influenza virus A test positive; Flu; Does not respond to the vaccine; This is a spontaneous case, initially received from other health professional on 16-Jan-2019, concerning 46-year-old adult female patient.  The patient did not have any medical history (reported as: no medications and surgeries). The patient's concomitant medication included Excerdin (acetaminophen, aspirin and caffeine).  On 01-Nov-2018, the patient was administered Flucelvax QIVc (influenza vaccine, subunit influenza virus vaccine polyvalent, cell culture derived, dose: 0.5 ml, route of administration: intramuscular, anatomical location: deltoid, batch number: 252664, expiry date: 30-Jun-2019) for active immunization against influenza disease caused by influenza A subtype viruses and type B viruses contained in the vaccine.  On 15-Jan-2019, 2 months and 14 days after administration of vaccine, the patient was diagnosed with flu after she made a visit to the doctor. The patient had a confirmatory test, flu A/B protein antigen, point od care test (POCT) was performed in which antigen A was confirmed. The patient believed that, she might be one of the persons that did not respond to the vaccine (coded as vaccination failure). The patient was treated with Ibuprofen and Mucinex (guaifenesin) through the whole time.  The patient recovered from the event influenza on 01-Feb-2019.  This case was associated with product quality complaint, hence quality assurance investigation (QAI) had been requested and the corresponding QAI reference number was 1039510. Based on the investigation performed, it was concluded that Flucelvax 252664 was manufactured in compliance with the approved internal procedures and in accordance with the quality requirements. No evidence was found that the lack of efficacy complaint was the result of the Fill Finish or Bulk manufacturing process at the facility and no trend was identified for the batch. Therefore, no internal root cause could be confirmed.  The reporter assessed the case as non-serious.  Follow up received from the reporter on 13-Feb-2019: The patient details were updated in the patient tab. The onset date (15-Jan-2019) and stop date (01-Feb-2019) of event flu was added. Hence, outcome of the event flu was changed from unknown to recovered in event tab. The lab investigation and new event influenza virus test positive were added in patient and event tab respectively. The concomitant medication (Excedrin) and treatment drugs (Ibuprofen and Mucinex) were coded in the product tab. It was reported that the patient did not have any medical history (no medications, no surgery). The narrative and case comment was amended accordingly.  Follow-up received from other health professional on 19-Mar-2019: Lab test was changed from 'influenza virus test' to 'influenza A virus test' in the patient tab. The event 'influenza virus test positive' was replaced with 'influenza virus A test positive' to be coded for the event. Reference number (QAIR number: 1039510) was added in the additional information tab. It was reported that flu A/B protein antigen, point of care test (POCT) was performed in which antigen A was confirmed and the test was not sensitive enough for substrain identification. The narrative was amended accordingly.  Follow up report received from Quality assurance department on 28-Mar-2019: Based on the investigation performed, it was concluded that Flucelvax 252664 was manufactured in compliance with the approved internal procedures and in accordance with the quality requirements. The narrative was amended accordingly.; Reporter's Comments: A 46-year-old female patient experienced Flu and reported vaccination failure, more than 2 months and 14 days after receipt of Flucelvax QIVc. The event flu was confirmed by the confirmatory diagnostic test. Time to onset is plausible following vaccination with the reported Influenza and vaccination failure events. Hence, company assessed the events as possibly related to suspect vaccine. The company assessed the case as serious (medically significant).