plunger would not go down completely and he is not sure of the amount of the dose delivered, no adverse event; plunger would not go down completely and he is not sure of the amount of the dose delivered, no adverse event; Pregnant women was administered FLUBLOK, no adverse event; Initial information regarding an unsolicited valid non-serious case was received from a Pharmacist via Agency (Reference number- 00786301) and transmitted to Sanofi on 27-Sep-2021.  This case involves a 38-year-old pregnant female patient who was administered INFLUENZA QUADRIVALENT RECOMBINANT VACCINE [FLUBLOK QIV] (exposure during pregnancy) and the plunger would not go down completely and the reporter was not sure of the amount of the dose delivered [(underdose) and (syringe issue)].  Data regarding this pregnancy were received prospectively, i.e. before pregnancy outcome was known.  The date of last menstrual period was not reported.  The estimated due date was not reported.  The gestation period at onset and gestation period at exposure was not reported.  The patient's past medical history, medical treatment(s), vaccination(s) and family history were not provided.  Concomitant medication(s) were not reported.  On 26-Sep-2021, the patient received a dose (0.5 ml; total) of suspect INFLUENZA QUADRIVALENT RECOMBINANT VACCINE (lot number: QFAA2115; expiry date: 30-Jun-2022) via intramuscular route in the left arm for prophylactic vaccination.  It was also case vaccine exposure during pregnancy (latency: same day).  The reporter mentioned, for the pregnancy, it was checked as 'YES' to the question: are you breast feeding, pregnant or planning to get pregnant but does not know anything further.  It was the case of actual medication error due syringe issue and vaccine underdose (latency: same day).  It was reported "Caller said they administered FLUBLOK PFS to patient. Caller said they are not sure if due to needle or syringe, but needle would not go all the way down resulting in the full dose not being administered. Caller asking if they should give patient second full dose. Pharmacist states he wasn't the one that gave the injection, and the product has been placed in the sharps. They do not want a replacement for it. States he doesn't know if it was the needle or the prefilled syringe but when administration was attempted the plunger would not go down completely and he is not sure of the amount of the dose delivered. States the box was not damaged and the needle didn't look bent."  Also, the reporter stated that the individual that was vaccinated was not trying to aspirate. The plunger was intact upon opening the carton. They had difficulty pushing the plunger during administration. There was no leakage reported. Number of units affected was one and it was not available for return because it was thrown in the sharps container.  No adverse events were reported at the time of this report.  At the time of this report, the outcome of the events was unknown.  At the time of this report, the outcome of the pregnancy was unknown.  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.