Facial swelling; General rash; Hives on unspecified areas; Local reaction such as itching, swelling in the left arm; Local reaction such as itching, swelling in the leftt arm; This is a spontaneous case, initially received from other health professional (nurse), via Merck Global Pharmacovigilance, to Communication (reference number: SEQ20-00217) on 14-Jan-2020, concerning a 4-year-old, male patient.   The patient's medical history and concomitant medications were not provided.  On 03-Jan-2020, the patient was administered unspecified flu vaccine [influenza virus vaccine polyvalent, anatomical location: right arm, dose, route of administration, batch number, expiration date: not reported] for an unknown indication.   On the same day, the patient was administered co-suspect Proquad [Measles vaccine live (Enders-Edmonston), Mumps vaccine live (Jeryl Lynn), Rubella vaccine live (Wistar ra 27/3), Varicella zoster vaccine live (Oka/Merck), anatomical location: left arm, dose, route of administration, batch number, expiration date: not reported] as routine vaccination, co-suspect Tdap [diphtheria vaccine toxoid, pertussis vaccine acellular, tetanus vaccine toxoid, anatomical location: left arm, dose, route of administration, batch number, expiration date: not reported] for an unknown indication, co-suspect HIB vaccine [HIB vaccine, anatomical location: left arm, dose, route of administration, batch number, expiration date: not reported] for an unknown indication and co-suspect IPV vaccine SSI [polio vaccine inact 3V (VERO), anatomical location: left arm, dose, route of administration, batch number, expiration date: not reported] for an unknown indication.  On 03-Jan-2019, shortly after the patient left the office after vaccination, the patient's parents called back the office and stated that the patient had a local reaction such as itching, swelling in the left arm.  On 04-Jan-2020, 24 hours after vaccination, the patient developed some facial swelling, general rash and hives on unspecified areas of his body. It was reported that the patient went to an unspecified urgent care, was administered Epi-Pen (epinephrine) and an unspecified dose of Benadryl (diphenhydramine hydrochloride) and sent to an unspecified Emergency Room to be monitored because of Epi-Pen administration. The patient was discharged from the Emergency Room the same day.  On an unspecified date in Jan-2020 the patient recovered from all the events.   The events of generalised rash, facial swelling and hives were considered as serious due to criterion of medical significance.  The reporter did not provide causality assessment to unspecified flu vaccine.  Company comment: The patient experienced swelling face, rash, urticaria, peripheral swelling and pruritus after vaccination with the suspect product, unspecified flu vaccine given in the right arm. Chronology is plausible. Co-suspect products, Proquad [Measles vaccine live (Enders-Edmonston), Mumps vaccine live (Jeryl Lynn), Rubella vaccine live (Wistar ra 27/3), Varicella zoster vaccine live (Oka/Merck), Tdap (diphtheria vaccine toxoid, pertussis vaccine acellular, tetanus vaccine toxoid), HIB vaccine (HIB vaccine), IPV vaccine SSI (polio vaccine inact 3V) were given in the left arm and on that arm localised events peripheral swelling and pruritus appeared so causal relationships between the events and flu vaccine is assessed as not related. No medical history, concomitant medications and diagnostic findings were provided.  Considering all the above mentioned, causality between suspect product and the events swelling face, rash and urticaria is assessed as related.; Sender's Comments: The patient experienced swelling face, rash, urticaria, peripheral swelling and pruritus after vaccination with the suspect product, unspecified flu vaccine given in the right arm. Chronology is plausible. Co-suspect products, Proquad [Measles vaccine live (Enders-Edmonston), Mumps vaccine live (Jeryl Lynn), Rubella vaccine live (Wistar ra 27/3), Varicella zoster vaccine live (Oka/Merck), Tdap (diphtheria vaccine toxoid, pertussis vaccine acellular, tetanus vaccine toxoid), HIB vaccine (HIB vaccine), IPV vaccine SSI (polio vaccine inact 3V) were given in the left arm and on that arm localised events peripheral swelling and pruritus appeared so causal relationships between the events and flu vaccine is assessed as not related. No medical history, concomitant medications and diagnostic findings were provided.  Considering all the above mentioned, causality between suspect product and the events swelling face, rash and urticaria is assessed as related.