This case was reported in a literature article and described the occurrence of suspected vaccination failure in a subject who received Flu vaccine unspecified for prophylaxis. On an unknown date, less than a year after receiving Flu vaccine unspecified, the subject developed vaccination failure. Serious criteria included GSK medically significant. Additional event(s) included influenza b virus infection, acute respiratory tract infection with serious criteria of GSK medically significant and cough. The outcome of vaccination failure was unknown. The outcome(s) of the additional event(s) included influenza b virus infection (unknown), acute respiratory tract infection (unknown) and cough (unknown). The investigator considered that there was a reasonable possibility that the vaccination failure, influenza b virus infection, acute respiratory tract infection and cough may have been caused by Flu vaccine unspecified. Relevant Tests: Lab tests were performed on unspecifed date. Nasal and oropharyngeal swabs (or nasal swabs alone for children aged less than 2 years) were collected to obtain respiratory specimens for detection and identification of influenza viruses by real-time reverse transcription-polymerase chain reaction (real-time RT-PCR). The patient was positive for influenza B/Victoria virus. Diagnostic results (unless otherwise stated, normal values were not provided): On an unknown date, Influenza virus test result was positive for influenza B/Victoria virus. On an unknown date, Polymerase chain reaction result was see text. Additional information was provided. This case was reported in a literature article and described the suspected vaccination failure in a patient aged equal to or more than 6-months of unspecified gender who was vaccinated with unspecified influenza vaccine (manufacturer unknown) for prophylaxis. This case corresponds to table 1 in this literature article. The patient was a part of the interim report that uses data from 3,254 children and adults enrolled in the Influenza Vaccine Effectiveness Network (Flu VE Network) during 23 November 2018 to 2 February 2019. No information on patient's family or medical history or concurrent condition or concomitant vaccination was provided. On an unspecified date during 2018-19 influenza season, the patient received equal to or more than 1 dose of unspecified seasonal influenza vaccine (administration route and site unspecified; dosages unknown; batch number not provided). Age of vaccination was not provided. On an unspecified date, equal to or more than 14 days after vaccination, the patient developed acute respiratory infection with cough. Subsequently, the patient was seeking outpatient medical care within 7 days of illness onset. Nasal and oropharyngeal swabs (or nasal swabs alone for children aged less than 2 years) were collected to obtain respiratory specimens for detection and identification of influenza viruses by real-time reverse transcription-polymerase chain reaction (real-time RT-PCR). The patient was positive for influenza B/Victoria virus. This case has been considered as suspected vaccination failure being time to onset was unknown. This case has been considered serious due to suspected vaccination failure. Treatment was unknown. The outcome of the event was not reported. The author did not comment on the relationship between the event of infection B infection and unspecified seasonal influenza vaccine. The author stated, "Vaccination prevents a substantial number of influenza-related illnesses, hospitalizations, and deaths annually. However, better protection and improved vaccination coverage are needed to realize the full potential of influenza vaccines. Evaluation of influenza vaccine effectiveness is an essential component of ongoing efforts to improve influenza vaccines. Influenza activity remains elevated, highlighting the importance of vaccination. CDC will continue to monitor influenza disease throughout the season to better understand the impact of vaccination, identify factors associated with reduced protection, and support efforts to improve influenza vaccines." Lab Comments: Lab tests were performed on unspecifed date. Nasal and oropharyngeal swabs (or nasal swabs alone for children aged less than 2 years) were collected to obtain respiratory specimens for detection and identification of influenza viruses by real-time reverse transcription-polymerase chain reaction (real-time RT-PCR). The patient was positive for influenza B/Victoria virus.