pregnant patient received a second dose of ADACEL in error with no reported adverse event; Initial information received on 24-Jan-2025 regarding an unsolicited valid non-serious case received from a other health professional. This case involves a 19-year-old pregnant female patient who was exposed to vaccine Diphtheria-2/Tetanus/5 AC Pertussis Vaccine [Adacel] second dose in error with no reported adverse event. Data regarding this pregnancy were received prospectively, i.e. before pregnancy outcome was known. The reported pregnant patient received a second dose of ADACEL in error with no reported adverse event occurred at unknown gestation period The date of last menstrual period was not reported. The estimated due date was not reported. The patient’s past medical history, medical treatment(s), vaccination(s) and family history were not provided. On 22-Jan-2025, the pregnant patient received a 0.5 ml dose (dose 2) of suspect Diphtheria-2/Tetanus/5 AC Pertussis Vaccine Suspension for injection of lot number: U8274AA and expiry date: 31-Aug-2026 via intramuscular route in the left deltoid in error also received dose 1 on 06-Dec-2024 with no reported adverse event (extra dose administered) (latency: on same day of 2nd dose). Reportedly, The patient is aware of the mistake and has not reported any reactions so far. This suspected adverse reaction report is submitted and classified as a medication error solely and exclusively to ensure the marketing authorization holder’s compliance with the requirements set out in the Directive 2001/83/EC and Module VI of the Good Pharmacovigilance Practices. The classification as a medical error is in no way intended, nor should it be interpreted or construed as an allegation or claim made by the marketing authorization holder that any third party has contributed to or is to be held liable for the occurrence of this medication error.