not feeling well; he felt really terrible yesterday; Fatigue; on the left side of his throat, it hurt to swallow/throat pain; on the left side of his throat, it hurt to swallow/throat pain; last night (07Apr2021), he had a really bad headache; Sensation of pressure in ear; Sensation of pressure in eye; Dizzy on standing; at one point, he had a little bit of nausea with the dizziness; he was really weak; he didn't eat yesterday because he had no appetite; Chills/Teeth chattering; Shaking; Hot feeling generalized; Sweating; Feeling hot and cold; on Tuesday night (06Apr2021) he didn't sleep well, and he could barely sleep last night (07Apr2021); his head felt heavy on Tuesday night (06Apr2021), and his head felt super heavy last night (07Apr2021); This is a spontaneous report from a contactable consumer (patient) via a Pfizer-sponsored Program COVAX US Support. A 23-year-old male patient received the second dose of bnt162b2 via an unspecified route of administration, administered in Left arm on 27Mar2021 (between 11:55AM and 12:00PM) (Lot Number: ER8732; Expiration Date: Jul2021) as single dose for covid-19 immunisation. The patient medical history and concomitant medications were not reported. The patient previously received the first dose of bnt162b2 via Intramuscular, at the age of 23-year-old, administered in right arm on 06Mar2021 (Lot Number: EN6206, Expiry: 30Jun2021) as single dose for covid-19 immunisation. He felt really terrible yesterday (07Apr2021). On Tuesday night (06Apr2021) he didn't sleep well, and he could barely sleep last night (07Apr2021). His head felt heavy on Tuesday night (06Apr2021), and his head felt super heavy last night (07Apr2021). On 07Apr2021, the patient experienced fatigue, on the left side of his throat, it hurt to swallow/throat pain, really bad headache, sensation of pressure in ear, sensation of pressure in eye, dizzy on standing, a little bit of nausea with the dizziness, really weak, he didn't eat yesterday because he had no appetite, chills/teeth chattering, shaking, hot feeling generalized, sweating, feeling hot and cold. The patient experienced not feeling well on an unspecified date. Patient started developing symptoms that were very bad, he thought he had COVID. Patient had a PCR test that was negative. Patient would like to know if a delayed response after second dose is normal. Reported he had received his second COVID-19 Vaccine dose about 2 weeks ago (27Mar2021). He said he felt really terrible yesterday. He said he felt so bad that he thought he had the COVID-19 Virus, and went to get tested. He clarified he had a real time COVID-19 Virus PCR test yesterday (07Apr2021), and received a negative result today (08Apr2021), less than 24 hours after having the test performed. He said it could be something else that was making him feel terrible. He said he had a (telehealth) appointment with a doctor tomorrow (09Apr2021). Caller asked if Pfizer had any data with the second COVID-19 Vaccine for people that had a really delayed immune response with their immune system. He said he had no symptoms after his second COVID-19 Vaccine, and was wondering if what he was experiencing now was a delayed immune response. Reported last night was the worst for his symptoms, saying it was awful. He said he felt better this morning. He clarified that on Tuesday night (06Apr2021) he didn't sleep well. He said his head felt heavy, but when he woke up, he did not feel too bad. He said he had fatigue, and on the left side of his throat, it hurt to swallow. He said last night (07Apr2021), he had a really bad headache, and his head felt super heavy. He said he had ear and eye pressure. He said he got dizzy on standing, and at one point, had a little bit of nausea with the dizziness. He said he wasn't sure if the nausea was caused by the dizziness. He said he was really weak, and didn't eat yesterday because he had no appetite. He said he took his temperature at around 8:00PM-9:00PM last night, and had no fever. He said he still had his sense of taste and smell. He said he had chills, he was shaking, and his teeth were chattering. He said he was also hot and sweating at times, like he was alternating between hot and cold. He said he tried to drink water yesterday, and would take a few sips of water when he turned over in bed. He said he could barely sleep. Treatment: Reported he took Ibuprofen 200mg tablets, off and on, to treat his headache because his headache was preventing him from sleeping. He said he would take 2 Ibuprofen 200mg tablets at a time. He said he took his first Ibuprofen dose in the middle of the night on Tuesday, and then took 2 more doses of 2 Ibuprofen 200mg tablets last night. He said he did not have the Ibuprofen 200mg tablet NDC, Lot, and Expiration Date because he had taken Ibuprofen from a different Ibuprofen 200mg bottle and put it in the Ibuprofen 200mg he was taking from. Reported he felt he had gained strength back today (08Apr2021) because he had showered this morning, and didn't fall over. He said he was so weak yesterday, even trying to text for his work was bad. He said his headache was a little worse today, and his left-sided throat pain was persisting, but everything else had subsided for now. Caller said he was wondering if what he had experienced was a delayed immune response, or a false negative COVID-19 Virus test, or something else, like Mono. Patient was not feeling well. Did test negative covid. The outcome of the event headache, Swallowing painful and Throat pain was not recovered, other events was recovering.  No follow-up attempts are needed. No further information is expected.