Initial unsolicited report received from the literature on 03-Oct-2017. This case was linked to cases 2017SA192773, 2017SA199352, 2017SA199353, 2017SA199354, 2017SA199355, 2017SA199356 (Same literature). Introduction: Febrile seizure is the most common type of seizure in childhood, occurring in up to 5% of children. 1 Febrile seizure can occur during infections with a variety of pathogens. 2,3 Febrile seizure has also been associated with certain types of vaccines. The timing of fever and febrile seizure after vaccination depends on whether the vaccine contains a live attenuated virus, which requires several days to replicate before inducing a febrile response, or contains inactivated components, which may elicit a febrile response within the first 24 hours. The febrile seizure risk with current live and inactivated vaccines has been studied in children ages six through 23 months, but not in younger children. 4, 5 The Advisory Committee on Immunization Practices (ACIP) recommends that all children less than six months old receive six vaccines to prevent eight infectious diseases. 6 There are five inactivated vaccines including HepB with doses recommended at birth and at one to two months of age, and DTaP, Hib, PCV, and IPV vaccines with doses recommended at two and four months of age. A live attenuated rotavirus (RV) vaccine is also recommended at two and four months of age. The febrile seizure literature reflects a lack of consensus about whether febrile seizure should be diagnosed in children less than six months of age. There are three frequently cited febrile seizure definitions that list different minimum ages. A National Institutes of Health consensus statement published in 1980 described febrile seizure as usually occurring between ages 3 months and 5 years. 7 In 1993, the International League Against Epilepsy defined febrile seizure as occurring in childhood after age one month. 8 In 2008, the Academy of Pediatrics published a simple febrile seizure clinical practice guideline that defined febrile seizure as occurring in children between ages six and 60 months. That document did not state the rationale for setting the lower age limit at six months, but a separate systematic review stated that, in practice, the lower age limit is generally considered to be six months because of the concern about serious infections such as meningitis presenting with seizure and fever possibly being mistaken for febrile seizure in children under six months. Our objective was to estimate the febrile seizure risk during the time from vaccination through the following day associated with vaccines administered to children aged one through five months. Materials and Methods The Vaccine Safety Datalink (VSD) is a collaboration between the Centers for Disease Control and Prevention and several integrated health care organizations (sites) that perform vaccine safety research and surveillance. Nine sites contributed data to the present study. The VSD population includes over eight million members annually and has been shown to be representative of the general population in terms of demographic and socioeconomic variations. We identified children in the VSD aged one to five months who had an emergency department (ED) visit or inpatient admission from July 1, 2006, through June 30, 2011, associated with an International Classification of Diseases, Ninth Revision (ICD-9) "convulsion" code (780.3, 780.31, 780.32, or 780.39), which include febrile seizure but not epilepsy. We excluded visits that occurred lessthan or equal to 42 days after a previous visit with a convulsion ICD-9 code because those are unlikely to represent a new event. We defined the day of vaccination as "day 0" and only included convulsion visits that occurred on days zero to one or 14 to 20 following the administration of one or more vaccines of any type. We abstracted medical records to determine whether each patient actually had an incident seizure and whether it was accompanied by a fever or not. We defined a "probable" seizure as a clinical diagnosis of seizure by the treating physician. We defined a "possible" seizure as a paroxysmal event for which the treating physician did not make a definitive diagnosis but for which seizure was considered the more likely possibility in the differential diagnosis. We defined fever as a temperature of greater than or equal to 38 degree C. We defined a febrile seizure as a seizure in a child who had a fever within the prior 24 hours, excluding patients with central nervous system (CNS) infection, criteria for other symptomatic seizures (e.g., brain structural abnormalities and metabolic disturbance), or a history of afebrile seizure. Seizures with fever that did not meet the febrile seizure definition were classified as "seizure with fever other than febrile seizure." This case involves two patients (age between one to five months and gender not specified), who were vaccinated with HAEMOPHILUS TYPE B (HIB) VACCINE (manufacturer: unknown) and PNEUMOCOCCAL CONJUGATE VACCINE and DTAP-HEPB-IPV (batch number, expiry date, dose, dose in series, route and site of administration were not reported) on unspecified dates. The patient's medical history and concomitant medications were not reported. On an unspecified date, following the vaccination (also reported as convulsion visits that occurred on same day to one day following the administration of one or more vaccines of any type or 14 to 20 following the administration of one or more vaccines of any type), the patients developed probable or possible febrile seizure. Patients were hospitalized on an unknown date (reported as nine patients were hospitalized). The probable febrile seizures all occurred in children aged three to five months, whereas the possible febrile seizures occurred from one to four months of age. Relevant laboratory test and corrective treatment was not reported. Outcome of event was not reported. It was stated that the reported seizure duration ranged from five seconds to five minutes. Documents held by sender: none.; Sender's Comments: A total of 2 patients experienced probable or possible febrile seizure after vaccination. Exact time to onset is not known. Further details regarding patient's medical history including birth history, previous vaccination history, history of similar episode, etiological workup and investigation reports to identify alternative etiology are needed for complete assessment of the case. Moreover, as multiple vaccines were administered concomitantly, the role of each component cannot be assessed separately.