Titer was measured on day 15 and was 0.2 international units per millilitre; Case reference number US-BN-2022-001832 is a spontaneous case report initially received on 09-Aug-2022 from a pharmacist via Communications (reference number: USBAV22-0891) and concerns a 29-year-old female patient.  The patient's medical history and concomitant medication details were not provided.  At an unknown date, the patient started taking Plaquenil (hydroxychloroquine sulfate), at an unknown dose or route of administration, for unknown indication.  On unspecified dates, reported also as days zero, three, seven and 14 the patient was vaccinated with the first four doses of RabAvert (rabies virus (inactivated, strain flury LEP) (PCEC); batch number: unknown), at a dose 1.0 mL, via unknown route of administration, for post-exposure prophylaxis.   At an unknown date, reported also as before the last RabAvert dose, the patient was recommended to stop taking Plaquenil.  On an unknown date, reported also as day 28, the patient was vaccinated with the fifth dose of RabAvert (batch number: unknown), at a dose 1.0 mL, via unknown route of administration .  On an unspecified date, reported also as 08-Jul and as 15 days after the first dose, titer was measured and the result was 0.2 IU/mL.  At the time of this report, the outcome for the event 'antibody test abnormal' was unknown.  The reporter assessed the event as non-serious and related to RabAvert.  The product quality complaint number received for this case is QE-001872.  Additional information received on 09-Aug-2022 included the local case ID, PQC number and patient's age.; Reporter's Comments: A 29-year-old female patient had a titer measured 15 days after the first dose (on the day zero, three, seven and 14 the patient was vaccinated with the first four doses of RabAvert) which is considered as antibody test abnormal. Antibody test abnormal is unlisted and unexpected according to guidelines for RabAvert. The outcome for the event antibody test abnormal was unknown. The patient's medical history and concomitant medication details were not provided. Reportedly, the patient started taking Plaquenil (hydroxychloroquine sulfate), at an unknown dose or route of administration, for unknown indication and it was recommended to stop taking Plaquenil before the last RabAvert dose. Considering plausible temporal relationship and since contributory role of the suspect product cannot be excluded, causality is assessed as related at this point. The case is considered as non-serious.; Sender's Comments: A 29-year-old female patient had a titer measured 15 days after the first dose (on the day zero, three, seven and 14 the patient was vaccinated with the first four doses of RabAvert) which is considered as antibody test abnormal. Antibody test abnormal is unlisted and unexpected according to guidelines for RabAvert. The outcome for the event antibody test abnormal was unknown. The patient's medical history and concomitant medication details were not provided. Reportedly, the patient started taking Plaquenil (hydroxychloroquine sulfate), at an unknown dose or route of administration, for unknown indication and it was recommended to stop taking Plaquenil before the last RabAvert dose. Considering plausible temporal relationship and since contributory role of the suspect product cannot be excluded, causality is assessed as related at this point. The case is considered as non-serious.