Vaccination failure; Type A flu; Fever; Stomach upset; Type A flu; This is a spontaneous case initially received from other health professional (nurse) on 05-Feb-2019, concerning a 06-year-old, male child patient.  The patient had no medical history and had not received any concomitant medications.  On 29-Sep-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 and 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 03-Feb-2019, 4 months and 5 days after vaccination, the patient developed fever and stomach upset. On 05-Feb-2019, the patient had a medical appointment with the paediatrician. On the same day, a nasal swab test was performed and was diagnosed with type A flu (influenza A virus test positive) (explicitly coded as vaccination failure). The patient was given Tamiflu (oseltamivir phosphate, from 05-Feb-2019 to 10-Feb-2019) for 5 days as antiviral treatment of flu and Zofran (ondansetron) as treatment or prevention of nausea and vomiting.  The outcome of the events was recovered on 10-Feb-2019.  The reporter assessed the case as non-serious.  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. No CAPA was required since the investigation has concluded that no internal root cause could not be determined.  Non-significant follow-up received from the quality assurance (QA) investigator on 05-Mar-2019: QAI reference number: 1039510 was added in the additional information tab. The narrative was amended accordingly.  Follow up received from other health professional on 20-Mar-2019: The email address of the primary reporter was added in the general tab. Added two new events fever (start date: 03-Feb-2019 and stop date 07-Feb-2019) and stomach upset (start date: 03-Feb-2019 and stop date 10-Feb-2019) as the symptoms of the event influenza A virus infection in the event tab. It was reported that a nasal swab test was performed on 05-Feb-2019, in the pediatric consultation which resulted positive for flu, type A. The stop date (09-Feb-2019) of the patient's treatment drug Tamiflu was added in the product tab. The start date of the event influenza A virus infection was changed from 05-Feb-2019 to 03-Feb-2019, stop date (10-Feb-2019) for the event influenza A virus infection was added. The outcome of the event influenza A virus infection was changed from not recovered to recovered in the event tab. Added reference number (Med Info Number: SEQ19-00827) in the additional information tab. The narrative was amended accordingly.  Follow-up received from the Quality Assurance (QA) department on 28-Mar-2019: QA investigation report was updated. 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 06-year-old male patient was diagnosed with type A flu, more than 4 months after receipt of Flucelvax QIVc (coded to influenza and vaccination failure). Considering the fact that vaccine needs minimum 2-3 weeks to provide immune protection against influenza, vaccination failure and causal role of suspect vaccine for the event influenza cannot be ruled out and were assessed as related to suspect vaccine.  The company assessed the event 'flu' as serious (medically significant).