those preparing the vaccines have mistakenly used Fluzone high-dose syringes/ Influenza vaccine mistaken as diluent meant for RSV vaccine; The diluent syringe for Abrysvo looks similar to the Fluzone highdose syringe, and the dark plunger stoppers make it difficult to read the labels; This is a spontaneous report received from a contactable reporter(s) (Pharmacist) from product quality group.  A patient (no qualifiers provided) received rsv vaccine prot.subunit pref 2v (ABRYSVO), as dose number unknown, single (Batch/Lot number: unknown) for immunisation; for immunisation; influenza vaccine inact split 3v (FLUZONE HIGH DOSE), as dose number unknown, single (Batch/Lot number: unknown) for immunisation. The patient's relevant medical history and concomitant medications were not reported. The following information was reported: PRODUCT PREPARATION ERROR (non-serious), described as "those preparing the vaccines have mistakenly used Fluzone high-dose syringes/ Influenza vaccine mistaken as diluent meant for RSV vaccine"; PRODUCT PACKAGING CONFUSION (non-serious), described as "The diluent syringe for Abrysvo looks similar to the Fluzone highdose syringe, and the dark plunger stoppers make it difficult to read the labels".  Causality for "those preparing the vaccines have mistakenly used fluzone high-dose syringes/ influenza vaccine mistaken as diluent meant for rsv vaccine" and "the diluent syringe for abrysvo looks similar to the fluzone highdose syringe, and the dark plunger stoppers make it difficult to read the labels" was determined associated to device constituent of rsv vaccine prot.subunit pref 2v (malfunction).  Additional information: Pharmacies reported two recent close calls involving patients who were supposed to concurrently receive FLUZONE (influenza highdose vaccine) and ABRYSVO (respiratory syncytial virus vaccine). Abrysvo is available in a vial containing lyophilized powder antigen. A practitioner must first dilute it using an accompanying syringe of sterile water for injection and a vial adapter. However, instead of connecting the Abrysvo diluent syringe to the vial, those preparing the vaccines have mistakenly used Fluzone high-dose syringes. Fortunately, in both cases, the error was recognized prior to administration. The diluent syringe for Abrysvo looks similar to the Fluzone highdose syringe, and the dark plunger stoppers make it difficult to read the labels. In addition, both the diluent syringe and the Fluzone syringe have Luer connectors, making them compatible with the vial adapter. A similar error could occur with other powdered vaccines when diluents and other vaccines kept nearby and are in prefilled Luer-lock syringes.   The information on the batch/lot number for (RSV VACCINE PROT.SUBUNIT PREF 2V) has been requested and will be submitted if and when received.  Follow-up (26Oct2023): This is a follow-up report from product quality group providing investigation results. Updated information: event updated as reportable malfunction.  The information on the batch/lot number for rsv vaccine prot.subunit pref 2v, rsv vaccine prot.subunit pref 2v  has been requested and will be submitted if and when received.; Sender's Comments: Linked Report(s) : US-PFIZER INC-202300334843 same reporter, product, evnet for different patients;