Tachycardia; Pressure on the left side of the chest; Blood pressure gone up; Pain all around to the back, feels relieved when folds on his knees; Pain all around to the back, feels relieved when folds on his knees; Hands really cold and sweaty; Hands really cold and sweaty; Heart palpitations go up; Blood oxygen go down (83%); A lot of tiredness; Headaches come and go; This spontaneous case was received on 19-Sep-2022 from other non-healthcare professional (consumer) via agency (reference number: SEQW22-03218) and concerned a 18-year-old, male patient.  The patient had no relevant medical history. The patient's concomitant medications were not reported (discrepant information reported as 'metoprolol'). The patient was in perfect health.  On 07-Sep-2022, the patient was vaccinated with Flucelvax Quadrivalent (influenza vaccine inact sag 4v; dose: 0.5 ml, route of administration and anatomical location: not reported) for prevention of influenza disease. The batch number reported was 942383 and expiry date: 10-Jun-2023.  On 08-Sep-2022, one day after receiving Flucelvax Quadrivalent, the patient experienced pressure on the left side of the chest, tachycardia, and his blood pressure gone up. Also, he experienced pain all around to the back and felt relieved when he folded on his knees.   On unspecified dates in Sep-2022, an unknown amount of time after receiving Flucelvax Quadrivalent, the patient got a lot of tiredness, his hands were really cold and sweaty, headaches would come and go, his blood oxygen went down to 83 % and heart palpitations went up. The patient was treated with metoprolol. As reported, there were six episodes and every episode was getting worse day by day.  On unspecified dates in Sep-2022, the patient had multiple emergency room visits.  On 19-Sep-2022, for the third time after visiting ER as reported, the patient was admitted to hospital.   At the time of the initial reporting, the patient had not recovered from the events.  The reporter assessed the events as related to Flucelvax Quadrivalent, as he was in a perfect good health before taking Flucelvax and asked if there was any kind of compensation for injuries with flu shots.  All events were considered to be serious due to seriousness criterion of hospitalization.  Company comment: A 18-year-old, male patient was vaccinated with the suspect product Flucelvax Quadrivalent. One day after vaccination the patient experienced pressure on the left side of the chest, tachycardia, increased blood pressure, back pain and general body pain. On an unspecified date within 11 days the patient developed fatigue, cold and sweaty hands, headaches, decreased oxygen saturation (down to 83 %) and palpitations. The patient was treated with metoprolol. As reported, there were six episodes and every episode was getting worse day by day. Information regarding the underlying medical history and related diagnostic findings was not provided. Due to limited information provided, causality for the events decreased oxygen saturation, chest pressure, increased blood pressure, cold and sweaty hands, tachycardia and palpitations is unassessable. Based on provided information causality for the remaining events is assessed as possibly related.; Reporter's Comments: The patient was in a perfect good health before taking Flucelvax and he asked if there was any kind of compensation for injuries with flu shots.; Sender's Comments: A 18-year-old, male patient was vaccinated with the suspect product Flucelvax Quadrivalent. One day after vaccination the patient experienced pressure on the left side of the chest, tachycardia, increased blood pressure, back pain and general body pain. On an unspecified date within 11 days the patient developed fatigue, cold and sweaty hands, headaches, decreased oxygen saturation (down to 83 %) and palpitations. The patient was treated with metoprolol. As reported, there were six episodes and every episode was getting worse day by day. Information regarding the underlying medical history and related diagnostic findings was not provided. Due to limited information provided, causality for the events decreased oxygen saturation, chest pressure, increased blood pressure, cold and sweaty hands, tachycardia and palpitations is unassessable. Based on provided information causality for the remaining events is assessed as possibly related.