Multiple seizures/ Had his first seizure on 11MAR/ Had multiple seizure during the day in the hospital.; Crying a lot; This spontaneous serious safety report with reference number 2023SA096424 (Inquiry number 01547120) was received by a partner on 24-MAR-2023 and forwarded on 27-MAR-2023 from a other health care professional.    A 4-month-old male patient had been vaccinated with the 1st dose of Vaxelis (Batch number U7255AA), on 07-MAR-2023 for immunization.   No medical history was provided.  Concomitant vaccination included Pneumococcal vaccine (PCP), (dose number unknown, Batch number unknown).  On 08-MAR-2023, two days after receiving the vaccination with Vaxelis, the patient was reported to be crying a lot, from 08-MAR-2023 until 10-MAR-2023. Five days after the vaccination with Vaxelis, on 11-MAR-2023, the patient experienced his first seizure. On 13-MAR-2023 the patient was admitted to the emergency room and was reported to have multiple seizure during the stay in the hospital. No treatment information was provided. The patient was discharged from the hospital on 17-MAR-2023.  At the time of this report, the outcome of the event was recovered/Resolved.    Action taken with Vaxelis was unknown.   The reporter did not provide an assessment of the causal relationship between Vaxelis and the reported events of "Multiple seizures/ Had his first seizure on 11MAR/ Had multiple seizure during the day in the hospital" and "Crying a lot".   Further information is expected.  COMPANY COMMENT:  Seizure is assessed as serious due to hospitalization. Crying was assessed as non-serious.   Seizure and crying are listed for Vaxelis as per the Safety Information.  Considering the current knowledge on Vaxelis (Seizure and Crying are listed as per safety information) and that the events appeared within one week after the vaccination and despite the lack of information (medical history, co-suspect vaccines), the causal relationship between Vaxelis and Seizure and Crying cannot be excluded and is assessed as related.   This single individual case safety report does not modify the benefit/risk balance of this product. Therefore, no change in the label or other measures is recommended at this time. However, the company will continue to monitor all respective reports received and based on cumulative experience, will re-evaluate the available evidence on an ongoing basis.; Sender's Comments: Seizure is assessed as serious due to hospitalization. Crying was assessed as non-serious.   Seizure and crying are listed for Vaxelis as per the Safety Information.  Considering the current knowledge on Vaxelis (Seizure and Crying are listed as per safety information) and that the events appeared within one week after the vaccination and despite the lack of information (medical history, co-suspect vaccines), the causal relationship between Vaxelis and Seizure and Crying cannot be excluded and is assessed as related.   This single individual case safety report does not modify the benefit/risk balance of this product. Therefore, no change in the label or other measures is recommended at this time. However, the company will continue to monitor all respective reports received and based on cumulative experience, will re-evaluate the available evidence on an ongoing basis.