postponed his second dose until they see what is going on and they improve his 02 sat; it will be 35 days this coming Monday since his first vaccine; Tachycardia; Sweating Profusely; Itching at the Injection Site; Very Tired; Low 02 Saturdationg; This is a spontaneous report from a contactable nurse. This contactable nurse reported for 63-year-old male patient (reporter's husband)  A 63-year-old male patient received first dose of BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE, solution for injection: Lot number: EWO709), via an unspecified route of administration on 17May2021 as a single dose for COVID-19 immunisation. Patient did not receive any other vaccines within 4 weeks prior to the COVID vaccine. Prior to vaccination, patient was not diagnosed with COVID-19. COVID prior vaccination was none. Historical vaccine included Hepatitis B vaccine. The patient's medical history included allergy, fatty liver, weight loss, Irritation of Nasopharynx, Granuloma (//2020). The caller stated that on May/2021, about less than 2 weeks after receiving the first dose, the patient started to feel very tired and his O2 saturation while resting was 90-93 on room air and with deep breathing he reached 95, but while he was laying down and sleeping it drops below 90. The reporter stated that the patient had no fever and no inflammation except a little itching at the injection site. The reporter also stated that the patient was excessively tired and sleeps every day. Stated that they didn't really pay attention to when tiredness started, but it was around the last week of May. The reporter stated that they had a weight trainer who comes to the house. The patient stated that her husband felt exhausted during the weight training and couldn't do his workout. Caller stated that she has tried to associate it with other things, the low 02 sat and said that it could be something else. It was reported that he has no coughing and no shortness of breath. It was stated that on 27May2021, her husband was really pooped. The reporter stated that she had him walked with the Pulse Ox and they went outside and had him run a little bit and do a little bit of cardio and his heart rate went up to. Caller stated that he was tachy and it stayed for a day after he ran and stated that it was after he ran in the evening and through the following day. Caller stated that he took some Raw Garlic because it helped when he was tachy before. Caller stated that her husband didn't directly complain of the arm side effects, it was more of her asking whether he was having any side effects, and he said just a little itch, no redness or swelling. The reporter stated that he was laughing about the shot, and had no body aches or tears, just itching on the deltoid area for just a few days and as time progressed, he started to feel more tired. Caller stated that the Low O2 Saturation has improved. Caller stated that she had him do the incentive spirometry and it was gradually starting to go up. Caller stated that they haven't checked his sleep tracking devices yet. Caller stated that on the same arm he wears a Garmin and a Fit Bit to make sure he was not going crazy. Caller stated that at night his O2 saturation level dropped to 88 for long periods of time. Caller stated that they ordered a Garmin night sleep tracking device from, towards the first of June. Caller stated that she was checking him with 2 pulse oximeters and then she ordered the Garmin on 01Jun2021. The reporter stated that low O2 saturation started towards the end of May, may be on 28-31 May. The patient had a physician office visit due to the events. Caller stated that they have postponed his second dose until they see what was going on and they wanted to improve his 02 saturation. Caller stated that the patient was able to walk 5 miles 2-3 times a week and did swimming. Caller stated that the patient was concerned about his low 02 saturation. Caller wanted to report this and the doctors did not know what to do with the second vaccine. Caller stated that it will be 35 days this coming (Monday) since his first vaccine. Caller was asking whether the low 02 Saturation can be a side effect of the vaccine. The patient underwent lab tests and procedures which included CT and pulmonary tests done with normal results. The patient o2 saturation level tests with unspecified results. The reporter assessed the events to be related with the suspect product. The outcome of the events was not resolved for fatigue, oxygen saturation decreased, unknown for 35 days this coming Monday since his first vaccine and resolved for other events.  Follow-up (17Jun2021)- Follow-up information was received from the same contactable nurse included non-clinical information  Information on Lot/Batch number was available. Additional information has been requested.; Sender's Comments: Based on temporal association, the causal relationship between BNT162B2 and the events cannot be excluded. The information available in this report is limited and does not allow a medically meaningful assessment. This case will be reassessed once additional information becomes available.