brain fog; Fatigue; Confusion; This is a spontaneous report received from a non-contactable reporter(s) (Consumer or other non HCP) from medical information team. The reporter is the patient.  A female patient in her 70's received bnt162b2 (BNT162B2) (Batch/Lot number: unknown) as dose 1, single for covid-19 immunisation. The patient's relevant medical history and concomitant medications were not reported. The following information was reported: FEELING ABNORMAL (non-serious) with onset 19Jun2021, outcome "not recovered", described as "brain fog"; FATIGUE (non-serious) with onset 19Jun2021, outcome "not recovered", described as "Fatigue"; CONFUSIONAL STATE (non-serious) with onset 19Jun2021, outcome "not recovered", described as "Confusion".  Additional information: Patient received her vaccination a week ago today. She was having brain fog, it waves in and out, fatigue and confusion, (brain fog, fatigue, confusion on Saturday (19Jun2021) but was still mild).The reporter noticed it intensified the next day (20Jun2021). It started Thursday and Friday she was fine. Then Saturday fatigue and Sunday it started. She clarified brain fog started on Sunday. She wants to know how long it would last. Her other question was that any medications that are being given, if a 300lb man, 6 ft tall would get the same vaccination as her, being 5ft tall and 96 or 97 lbs. Even her granddaughter who is 13. Pfizer needs to adjust the dose based on the size of the person. Product strength and count size dispensed: wanted to know how long the adverse events that she got after the first dose of the Pfizer BioNTech Covid-19 Vaccine would potentially last. Reporter wanted to know if it would be fine for her to take the 2nd shot of the Pfizer BioNTech Covid-19 Vaccine a day early or later than the recommended 21 days from the first dose. Response: Spoke from attached document Revised: 19May2021. Reporter was interested to know the reason why it had to be specifically 3 weeks exactly for a patient to receive the 2nd dose of the Pfizer BioNTech Covid-19 Vaccine from the first dose. "Is it to make you forget all of the adverse events that you got from the first dose?" Response: Spoke from attached document. Product: PFIZER-BIONTECH COVID-19 VACCINE. Reporter also wanted to know if the dosage of the Pfizer BioNTech Vaccine was the same all throughout varying population groups. "Is the dose for a 6 FT and 350 LBs man the same for a 5 FT tall woman". Response: Spoke from PI and attached document: (privacy). "Pfizer and BioNTech have initiated a Phase 1 study in individuals less than 12 years of age. Phase 1 is the open-label dose finding portion of the study to evaluate safety, tolerability, and immunogenicity of Pfizer-BioNTech COVID-19 vaccine on a 2-dose (separated by approximately 21 days) schedule in up to 3 age groups. The "> 5 years to <12 years of age" cohort will be randomized to receive one of three doses: 10 mcg, 20 mcg, or 30 mcg. After analysis of the Phase 1 results, one dose for this cohort will likely move forward into Phase 2-3 study. Phase 2/3 will evaluate the safety, tolerability, and immunogenicity in each age group at the selected dose level from Phase 1" No information specific to varying dosage for specific population groups. Reporter stated that she was hoping for more studies to be conducted about altering the dosage for specific population groups. She stated that she was noticing longer duration of side effects for petite women as compared to other population and she wants us to be aware of this,  Product: PFIZER-BIONTECH COVID-19 VACCINE.   No follow-up attempts are possible; information about lot/batch number cannot be obtained. No further information is expected.