Influenza virus infection; Sinusitis; Orbital cellulitis; pott's puffy tumor; pott's puffy tumor; Peptostreptococcus/Streptococcus mitis/ Streptococcus anginosus; polymicrobial infection with Prevotella; This case was reported in a literature article and described the occurrence of influenza in a 12-year-old male patient who received Flu unspecified (Flu vaccine) for prophylaxis. Co-suspect products included PNEUMOCOCCAL VACCINE (PNEUMOCOCCAL 7-VALENT CONJUGATE VACCINE) for prophylaxis.   Previously administered products included PNEUMOCOCCAL 7-VALENT CONJUGATE VACCINE (1st 3 doses received on unknown date).   On an unknown date, the patient received Flu vaccine at an unknown dose and the 4th dose of PNEUMOCOCCAL 7-VALENT CONJUGATE VACCINE. On an unknown date, unknown after receiving Flu vaccine, the patient experienced influenza (serious criteria hospitalization), sinusitis (serious criteria hospitalization), orbital cellulitis (serious criteria hospitalization and GSK medically significant), subperiosteal abscess (serious criteria hospitalization and GSK medically significant), osteomyelitis (serious criteria hospitalization and GSK medically significant), streptococcal infection (serious criteria hospitalization) and bacterial infection (serious criteria hospitalization). The subject was treated with ceftriaxone and metronidazole. On an unknown date, the outcome of the influenza, sinusitis, orbital cellulitis, subperiosteal abscess, osteomyelitis, streptococcal infection and bacterial infection were recovering/resolving.   The reporter considered the influenza, sinusitis, orbital cellulitis, subperiosteal abscess, osteomyelitis, streptococcal infection and bacterial infection to be related to Flu vaccine.  Additional details were reported as follows: This case was reported in a literature article and described the occurrence of influenza virus infection (type unknown) in a 12-year-old male patient, who was vaccinated with unspecified influenza vaccine (manufacturer unknown) for prophylaxis. This case corresponds to case-3 from table 1 reported in this literature article. The patient was a part of retrospective review that was performed for pediatric patients hospitalized with bacterial head or neck infections following influenza infection between October 2017 and March 2018. No information on patient's medical history, family history or concurrent condition or concomitant medication was provided. On an unspecified date, the patient received unspecified influenza vaccine (administration route and site unspecified, dosage unknown; batch number not provided). It was reported that, the patient had not received in the current 2017-2018 seasonal influenza vaccine. The patient had also received 4 doses of unspecified 7-valent pneumococcal conjugate vaccine (PCV7). The age of vaccinations was not provided.  On an unspecified date, an unknown period after the seasonal influenza vaccination, the patient developed influenza virus infection that was subsequently diagnosed with positive rapid influenza diagnostic test. The type of influenza virus was unknown. On an unspecified date between October 2017 and March 2018, at the age of 12 years, 4 days after the influenza diagnosis, the patient was hospitalized for sinusitis, pott's puffy tumor and orbital cellulitis (bacterial head or neck infections which were associated with influenza infection). The endoscopic sinus surgery (ESS) was performed. The causative pathogen for head or neck infection was found to be Streptococcus anginosus group. The patient was also found positive with polymicrobial infection with Peptostreptococcus, Prevotella and S.mitis. The duration of hospitalization was between 5 and 35 days. The treatment was started with ceftriaxone and metronidazole (definitive treatment). The duration of treatment was 5 weeks. The patient had completed ceftriaxone and metronidazole treatment successfully and had favorable outcome.  This case has been considered as serious due to hospitalization. The author did not comment on the relationship between the event of influenza virus infection, and unspecified seasonal influenza vaccine. However the authors stated, "Seasonal influenza infection is associated with secondary bacterial complications involving the upper and lower respiratory tract. However, the association of influenza infection with secondary severe or complicated head and neck infections is not appreciated." The authors concluded, "It was suggested that complicated bacterial head and neck infections may represent an under recognized co-infection or secondary complication of infection with influenza virus, further stressing the importance of prevention and treatment of influenza infection." This article corresponding to this case is not available for regulatory submission due to copyright restriction. This is 1 of the 2 valid cases reported in this literature article.      Lab Comments: On an unspecified date between October 2017 and March 2018, lab test were done. The causative pathogen for head or neck infection was found to be Streptococcus anginosus group. The patient was also found positive with polymicrobial infection with Peptostreptococcus, Prevotella and S.mitis