seizures; pediatrician said that the motions that the patient was experiencing were because of gas; the patient was not reacting to her (the mother) the same way; The back arching usually occurred right after the patient went to sleep; pediatrician said that the motions that the patient was experiencing were because of gas; Initial information received on 15-Aug-2023 regarding an unsolicited valid serious case received from a consumer/non-hcp.  This case involves a 2 months old female patient who experienced seizures, the patient was not reacting to her (the mother) the same way, the back arching usually occurred right after the patient went to sleep and pediatrician said that the motions that the patient was experiencing were because of gas after receiving vaccine Diphtheria/Tetanus/5 Hybrid AC pertussis/IPV(VERO)/HIB(PRP/T) vaccine [Pentacel (VERO)].  The patient's past medical history, medical treatment(s), vaccination(s) and family history were not provided.  Concomitant medications included Rotavirus Vaccine and Pneumococcal Vaccine CONJ 13V (CRM197) (PREVNAR 13) both for Prophylactic vaccination.  On an unknown date, the patient received a dose (1x) of suspect Diphtheria/Tetanus/5 Hybrid AC pertussis/IPV(VERO)/HIB(PRP/T) vaccine suspension for injection with unknown strength, batch number & expiry date via unknown route in unknown administration site for Immunization.  Information on the batch number was requested.  On an unknown date the patient seizures (seizure), pediatrician said that the motions that the patient was experiencing were because of gas (flatulence) & (diarrhoea), the patient was not reacting to her (the mother) the same way (hyporesponsive to stimuli) and the back arching usually occurred right after the patient went to sleep (opisthotonus) (unknown latency) following the administration of Diphtheria/Tetanus/5 Hybrid AC pertussis/IPV(VERO)/HIB(PRP/T) vaccine.   Relevant laboratory test results included: Electroencephalogram - On an unknown date:  [seizures]  Action taken: not applicable.  It was not reported if the patient received a corrective treatment for all the events.  At time of reporting, the outcome was Recovered / Resolved on an unknown date for the events seizures, pediatrician said that the motions that the patient was experiencing were because of gas, was Unknown for the events the patient was not reacting to her (the mother) the same way and the back arching usually occurred right after the patient went to sleep.  Seriousness Criteria: Medically Significant and Hospitalization for the event Seizure.; Sender's Comments: Sanofi Company Comment dated 22-Aug-2023: This case involves a 2 months old female patient who experienced seizures after receiving vaccine Diphtheria/Tetanus/5 Hybrid AC pertussis/IPV(VERO)/HIB(PRP/T) vaccine [Pentacel (VERO)]. Further information regarding Past medical history, concurrent condition, concomitant medication and tolerance, allergic history, Hospitalization details, laboratory investigations excluding alternative etiologies for the reported events are needed to fully assess this case. Based upon the reported information, the role of a vaccine cannot be excluded. But due to multiple vaccines administered at the same time, it can be hard to point one causative agent.