Vaccination Failure/Lack of efficacy; Swab test was performed and the result was positive for flu type A; Cold symptoms; Sore [/scratchy] throat; Fever; Fatigue; Scratchy throat; Dizziness; Body aches; Congestion; Flu, type A; This is a spontaneous case, initially received from other health professional on 22-Feb-2019, concerning a 27-year-old adult male patient.  The patient's relevant medical history was unknown. The patient did not administer any other medications at the time of vaccination.  On 04-Dec-2018, the patient was administered Flucelvax QIVc (influenza vaccine, subunit influenza virus vaccine polyvalent, cell cultured derived, dose: 0.5 ml, route of administration: intramuscular, anatomical location: deltoid, batch number: 252664 and expiry date: 20-Jun-2019) for influenza prophylaxis.  On 19-Feb-2019, 2 months and 15 days after the administration of the vaccine, the patient experienced mild cold symptoms, fever, fatigue, sore and scratchy throat, dizziness, congestion and body aches. On 22-Feb-2019, the patient visited urgent care clinic, as the mild cold symptoms did no disappear, where swab test was performed, and the result was found to be positive for flu type A. On 22-Feb-2019, the symptoms got worsened and continued throughout the Sunday (24-Feb-2019). On 25-Feb-2019 (reported as Monday), the symptoms began to diminish.  As a treatment, the patient received Tamiflu (oseltamivir phosphate, from 22-Feb-2019 to 26-Feb-2019) and prednisone (from 22-Feb-2019 to 26-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. No CAPA is required since the investigation has concluded that no internal root cause could not be determined.  The outcome of the events was recovered on 27-Feb-2019 (the patient was fully symptom free).  The reporter assessed this case as serious (medically significant).  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 the Quality Assurance (QA) department on 28-Mar-2019: QA investigation report was updated. The narrative was amended accordingly.  Follow-up received from the other health professional on 09-Apr-2019: The start date (22-Feb-2019) and stop date (26-Feb-2019) of the treatment drug Tamiflu and the start date (22-Feb-2019) and stop date (26-Feb-2019) of the treatment drug prednisone was added in the product tab. The outcome of the event influenza and its symptoms cold symptoms, throat irritation, pyrexia, fatigue, dizziness, nasal congestion and body aches was updated from not recovered to recovered with stop date 27-Feb-2019 in event tab. The narrative was amended accordingly.; Reporter's Comments: A 27-year-old male patient experienced mild cold symptoms, fever, fatigue, sore/scratchy throat, dizziness, congestion and body aches, and was diagnosed to have influenza, 2 months and 15 days after Flucelvax QIV vaccination (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 case as serious (medically significant).