Vaccination failure; Feeling hot and cold; Fever was recorded at 103; Chills; Feeling achy; Flu/ it was strain A; This is a spontaneous case, initially received from other health professional on 18-Mar-2019, concerning a 37-year-old, adult male patient.  The relevant medical history of the patient included seasonal allergies that started about 10 years ago (exact date was not known) and was ongoing. The patient was generally healthy with no other medical issues. The concomitant medication of the patient included fluticasone (reported as generic Flonase) that the patient took most days for seasonal allergies since a couple of years ago (exact date was not known).  On 29-Sep-2018, the patient was administered Flucelvax QIVc (influenza vaccine, subunit influenza virus vaccine polyvalent, cell cultured derived, batch number: 252664, expiration date: 30-Jun-2019, dose, route of administration and anatomical location: not reported) for active immunization against influenza.  On 18-Mar-2019, 5 months and 17 days after the vaccination the patient began feeling achy but showed no other symptoms. On 20-Mar-2019, the patient became symptomatic and was feeling hot and cold, fever was recorded as 103 and chills. The patient went to urgent care and was diagnosed with flu on the same day (explicitly coded as vaccination failure). The doctor said it was strain A but did not document it so there was no further information available about the strain testing. The patient was treated with acetaminophen (start date: 20-Mar-2019 and stop date: 21-Mar-2019) and ibuprofen (start date: 20-Mar-2019 and stop date: 21-Mar-2019) for flu. It was reported that the patient was not hospitalized.  The diagnostic test was not available, but it was verbally communicated about the strain type, which had no documentation.  The outcome of all the events was recovered on 21-Mar-2019.  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 can be 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 and no trend was identified for the batch. Therefore, no internal root cause could be confirmed.   The reporter assessed this case as serious (medically significant).  Non-significant follow up received from the other health professional on 28-Mar-2019: The reporter confirmed that, diagnosis date of flu was 20-Mar-2019, in original email it was misspelled, but confirmed as 20-Mar-2019. The reporter confirmed that diagnostic test was not available, but it was verbally communicated about the strain type, which had no documentation. The med Info Number (SEQ19-01198) and Company Number (US-SEQIRUS-201902693) were added in additional information tab. The narrative was amended accordingly.  Follow up report received from Quality assurance department on 28-Mar-2019: Based on the investigation performed, it can be 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 37-year-old male patient experienced pain, hot and cold, fever and chills and was diagnosed to have influenza, 5 months 18 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. Further assessment will be done upon receipt of new information. The company assessed the case as serious (medically significant).