Suspected vaccination failure; Influenza A; This case was reported in a literature article and described the occurrence of vaccination failure in a child patient who received Flu Seasonal TIV Dresden (Flu trivalent vaccine) for prophylaxis.   On an unknown date, the patient received the 1st dose of Flu trivalent vaccine. On an unknown date, more than a week after receiving Flu trivalent vaccine, the patient experienced vaccination failure (serious criteria hospitalization and GSK medically significant) and influenza a virus infection (serious criteria hospitalization). On an unknown date, the outcome of the vaccination failure and influenza a virus infection were unknown.  The reporter considered the vaccination failure and influenza a virus infection to be related to Flu trivalent vaccine.  Additional details were provided as follows: This case was reported in a literature article and described the suspected vaccination failure in a patient aged between 2 and 8 years of unspecified gender, who was vaccinated with unspecified trivalent inactivated influenza vaccine (TIV) (manufacturer unknown) for prophylaxis.  This was a test-negative design study that examined data retrospectively over 3 influenza seasons. It was estimated vaccine effectiveness (VE) against influenza hospitalization among children aged 6 months to 8 years at hospitals in the 2015-2016, 2016-2017, and 2017-2018 influenza seasons, using the test-negative design. For each season, it was estimated VE for fully and partially vaccinated children, using complete vaccine receipt histories from birth. [Individuals were excluded if they received their vaccine less than 14 days before hospitalization, received the live attenuated influenza vaccine or quadrivalent inactivated vaccine (QIV) in the current influenza season, were hospitalized outside the influenza season, or were tested for influenza more than 10 days after hospital admission. It was considered the beginning of the season to be the week when the first influenza positive sample was reported, and the end of the season to be the week when sentinel surveillance ended, based on MoH surveillance. Comorbid conditions were defined for the 2 years before hospitalization. It was included 326 influenza-positive case patients and 2821 influenza-negative controls (140 case patients and 971 controls from 2015-2016, 36 case patients and 1069 controls from 2016-2017, and 150 case patients and 781 controls from 2017-2018)]. The patient did not receive the live attenuated influenza vaccine (LAIV) or quadrivalent inactivated vaccine (QIV) in the current influenza season. The patient were not hospitalized outside the influenza season. The patient had at least one comorbidity (unspecified) for the 2 years before hospitalization. No information on patient's medical history, family history, or concurrent condition was provided. On an unspecified date from 1 September of the 2016-2017 influenza season, the patient received partial vaccination of unspecified trivalent inactivated influenza vaccine (TIV) (administration route and site unspecified, dosage unknown; batch number not provided). The age of vaccination was not provided. [Vaccination is the most effective strategy for prevention of influenza-related illness and is recommended annually by the Ministry of Health (MoH) and the Advisory Committee on Immunization Practices for individuals aged more than or equal to 6 months. Both recommendations specify that children aged 6 months through 8 years receive 2 doses of influenza vaccine if they have not received more than 1 influenza vaccine previously. Vaccinated individuals were those who had received TIV from 1 September of the influenza season of interest and more than or equal to 14 days before hospital admission. Fully vaccinated individuals were those who had received a current season vaccine (TIV only) and had received more than or equal to 2 influenza vaccines previously, or had received 2 current season vaccines more than or equal to 14 days apart. Partially vaccinated individuals were those who had received a current season vaccine and did not meet the criteria for full vaccination. During 2016-2017, children in second grade received influenza vaccine in school, but records of these vaccinations were not routinely entered into the electronic medical record. To evaluate the impact of these potentially incomplete vaccination records, it was conducted 2 additional analyses; it was removed 2016-2017 data from the overall VE estimate, and estimated influenza VE in the 2016-2017 excluding individuals more than 5 years old as of 1 September 2016]. The patient had received a current season vaccine (TIV only) and had not received more than or equal to 2 influenza vaccines previously, or had not received 2 current season vaccines more than or equal to 14 days apart. The patient received the vaccine more than or equal to 14 days before hospitalization. On an unspecified date between 8 October 2016 and 16 April 2017 in 2016-2017 influenza season, less than 10 days after hospital admission, the patient was tested for influenza. [Influenza case patients were individuals who tested positive for influenza by reverse-transcription polymerase chain reaction (RT-PCR) during a hospital admission. The majority of these hospitalizations were in children who were male (55.2%), aged 6 months to less than 2 years old (60.7%), and had more than or equal to 1 comorbid condition (54.3%). The 2016-2017 season had few positive specimens (n = 36), all influenza A. The 2015-16 season occurred between 11 October 2015 and 16 April 2016, the 2016-17 season between 8 October 2016 and 16 April 2017. For the 2017-18 season, it was included hospitalizations from 21 October 2017 through 18 March 2018, the latest date that data were available at the time of analysis, and three weeks before the end of the influenza season]. The patient had tested positive for influenza A by RT-PCR during hospital admission. This case has been considered as suspected vaccination failure being the time to onset was unknown. This case has been considered as serious due to suspected vaccination failure and hospitalization. Treatment was unknown. The outcome of the event was not reported. The author did not comment on the relationship between the event of influenza A infection and unspecified trivalent inactivated influenza vaccine (TIV). The author stated, "This study, the first to evaluate influenza VE against hospitalization, found that influenza vaccine was effective in preventing hospitalization associated with laboratory-confirmed influenza in fully vaccinated children aged 6 months to 8 years across 3 influenza seasons. Among fully vaccinated children, the vaccine was effective against influenza A in 2 of 3 seasons and against influenza B in 2017-2018. Estimated VE for partial vaccination was consistently lower than VE for full vaccination. Young children are at high risk for severe influenza-related outcomes, including hospitalization and death. Delayed hospital presentation could increase the likelihood of false-negative RT-PCR results if the infection has cleared before testing. VE. To reduce inclusion of false-negative results, it was excluded individuals who were tested more than 10 days after hospital admission. It was included individuals tested up to 10 days before admission because previous study findings suggest that children may shed influenza for a long time, with a substantial decrease in shedding after 10 days." The author concluded, "It was found influenza vaccine to be effective against hospitalization for laboratory-confirmed influenza in fully vaccinated children aged 6 months to 8 years from 2015 to 2018. The VE for partial vaccination was consistently lower than for full vaccination. There was also high VE against influenza A in 2015-2016 and 2016-2017 and against influenza B in 2017-2018. It was found evidence for cross-lineage protection from vaccination when TIV included B/Victoria but not when TIV included B/Yamagata, though these estimates rely on small sample sizes and have wide CIs. The findings suggesting that influenza VE reduces the risk for severe disease in children further strengthen current recommendations for annual influenza vaccine in children. The higher VE for children who were fully vaccinated is consistent with current guidelines that recommend 2 vaccines for vaccine-naive children through age 8." This is 1 of the 2 valid cases reported in the same literature article.      Lab Comments: Lab test done on an unspecified date between 8 October 2016 and 16 April 2017.