chronic hyponatremia; Nausea; vomiting; Headache; weak; This is a spontaneous report received from contactable reporter(s) (Nurse). The reporter is the patient.  A 78-year-old female patient received BNT162b2, BNT162b2 omi ba.4-5 (BNT162B2, BNT162B2 OMI BA.4-5), on 18Dec2022 as dose 4 (booster), single (Lot number: GJ6742) at the age of 78 years, in left arm for covid-19 immunisation. The patient's relevant medical history included: "Coronary artery disease" (unspecified if ongoing), notes: Comments: Coronary artery disease; "she is a heart patient" (unspecified if ongoing), notes: Went to hospital Wednesday because, she is a heart patient. They thought she was having a heart attack.; "blood thinners" (unspecified if ongoing), notes: blood thinners. The patient took concomitant medications. Vaccination history included: BNT162b2 (First Dose: 25Feb2021, LOT: EN6955, NDC, EXP: Unknown), administration date: 25Feb2021, when the patient was 77-year-old, for Covid-19 immunization, reaction(s): "MI"; BNT162b2 (Second Dose: 01Jul2021, LOT: EW0198, NDC, EXP: Unknown), administration date: 01Jul2021, when the patient was 77-year-old, for Covid-19 immunization; BNT162b2 (Third Dose: 09Feb2022, LOT: FM0698, NDC, EXP: Unknown), administration date: 09Feb2022, when the patient was 78-year-old, for Covid-19 immunization. The following information was reported: HYPONATRAEMIA (hospitalization), outcome "unknown", described as "chronic hyponatremia"; NAUSEA (hospitalization), outcome "not recovered"; VOMITING (hospitalization), outcome "unknown"; HEADACHE (hospitalization), outcome "unknown"; ASTHENIA (non-serious), outcome "not recovered", described as "weak". The patient was hospitalized for hyponatraemia, nausea, vomiting, headache (start date: 21Dec2022, discharge date: 24Dec2022, hospitalization duration: 4 day(s)). The events "chronic hyponatremia", "nausea", "vomiting", "headache" and "weak" required physician office visit and emergency room visit. The patient underwent the following laboratory tests and procedures: Blood sodium: low; Test: everything was fine, notes: They did  all the tests even again and everything was fine.  Additional Context: Call regarding latest Pfizer Omicron Bivalent vaccine. She was hospitalized and had the vaccine Sunday. The next 2 days, stayed home and Wednesday morning went in to the hospital with chronic hyponatremia. Had nausea vomiting, headache, is nearly 79 years old, which she will be in 2 weeks. Wishes she never had it. Has not been sick like this in years. She was told the vaccine was only tried on mice and, Pfizer was rushing through these vaccines with no approval from the FDA, just through emergency orders. Spoke to 2 doctors, one who discharged her, when she was hospitalized over Christmas. Both doctors assured her that the Pfizer booster has 2 subvariants like double doses than the previous booster. They, sadly, are not allowed to talk about it or place a diagnosis on her discharge papers. It is all political. Patient weight was 126, was not weighed upon discharge but has appointment next week with primary. Hope sit is no more than 120. Is still recovering. Has not seen her yet, it was a terrible reaction. She is through. Next appointments Tuesday, after the new year with the FDA. Is not doing the CDC because you can only do that online and is not well enough to do that. Chronic hyponatremia, From there, had no symptoms right away. went to hospital because, she was a heart patient. They thought she was having a heart attack. She went by ambulance to the hospital. Came out Christmas eve, 24Dec2022. was home a couple of days, was really weak. Went right back to urgent care at. They kept her there all day. Sodium was a little better but still low. went back in because she had choked on some small amount of food, what little food she was eating. Came home that same day about 7 hours later, was not admitted that time. Still has nausea and is very weak. Apparently, her lungs are fine. Thinks there is a lot of other people put there with far more worse reactions that she had. She was one of the lucky ones. Relatedness of drug to reaction(s)/event(s): Source of assessment: Primary Source Reporter, Method of assessment: Global Introspection. Result of Assessment: Yes.  Reporter details: Retired nurse, RN, is 79 years old. Should have know n better that to receive this vaccine.   Causality: Most definitely this was all caused by the Omicron Bivalent booster. Was fine before and had'nt caught the flu or anything from anyone else.; Sender's Comments: Based on the available information and close temporal association, a possible causal relationship cannot be excluded between the suspect vaccine BNT162b2 and the reported events "hyponatremia", "vomiting", "headache", "nausea". The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.,Linked Report(s) : US-PFIZER INC-202300002475 Same patient, different vaccine dose number and different event.;US-PFIZER INC-202300002476 Same patient, different vaccine dose number and different event.;