Vaccination failure; Was out of work; Positive for Type A influenza; Chills; Fever; Body ache; Cough; Sore throat; Headache; Sinus drainage; Flu type A; This is a spontaneous case, initially received from other health professional (nurse) on 13-Feb-2019, concerning a 40-year-old, adult female patient.  On 09-Oct-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: left deltoid, batch number: 252664 and expiry date: 30-Jun-2019) for influenza prophylaxis.  On 10-Feb-2019, 4 months and 1 day after vaccination, the patient developed chills, fever, body ache, cough, sore throat, headache, sinus drainage and was diagnosed with flu (explicitly coded as vaccination failure). On 12-Feb-2019, unspecified influenza test performed showed positive type A strain of influenza. The patient was given 5-day prescription of Tamiflu (12-Feb-2019 to 16-Feb-2019). It was reported that, the patient was out of work from 13-Feb-2019 to 19-Feb-2019.  On 19-Feb-2019, the patient was feeling better.   On 23-Feb-2019, the patient had completely recovered from the event flu.  This case was associated with product quality complaint, hence quality assurance investigation (QAI) had been requested and the corresponding QAIR 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 this case as non-serious.  Non-significant follow up received from the reporter on 26-Mar-2019: It was reported that, attempts were made on 26-Feb-2019 and 14-Mar-2019 to reach the reporter, however the reporter could not be reached. A third attempt would be made to reach the reporter for additional information. Medical information reference number (SEQ19-00874) was added in the additional information tab. No changes were done in the narrative.  Follow-up received from other health professional on 29-Mar-2019: Added new events chills, fever, body ache, cough, sore throat, headache (considered as flu symptoms), impaired work ability, Influenza A virus test positive and vaccination failure. Added start date of the event flu (10-Feb-2019). On an unspecified date, sinus drainage was performed. On 12-Feb-2019, unspecified influenza test was performed which showed positive result for type A influenza. The patient was given 5-day prescription of Tamiflu. The outcome of the event flu was changed from 'not reported' to 'recovered' as the symptoms resolved by 23-Feb-2019. The causality of the event flu' was changed from unassessable' to related'. This case was associated with product quality complaint, hence quality assurance investigation (QAI) had been requested and the corresponding QAIR 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. The narrative was amended accordingly.  Follow-up received from other health professional on 10-Apr-2019: Added start date (10-Feb-2019) and stop date (23-Feb-2019) for the events chills, fever, pain, cough, sore throat and headache. The reporter confirmed that, sinus drainage was the symptom of the event flu. Added treatment medication Tamiflu for flu (from 12-Feb-2019 to 16-Feb-2019). The narrative was amended accordingly.; Reporter's Comments: A 40-year-old female patient experienced symptoms of influenza, 4 months 1 day after receipt of Flucelvax QIVc and was diagnosed with flu type A (influenza), 4 months 3 days post vaccination (considered as 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. Hence, the events influenza and vaccination failure assessed as related to suspect vaccine. The patient experienced impaired work ability, 4 months 4 days post vaccination. The event impaired work ability assessed as not related, as it can be alternatively explained by the event influenza. The company assessed the case as serious (medically significant).