Pfizer booster; my armpit and into like my what feels like my breast is also really painful; when my arm is just in rest I feel pain. When my arm is at rest and I am not moving it, I feel pain in my elbow; When my arm is at rest and I am not moving it, I feel pain in my elbow; have a pain shooting down my knee at this point; This is a spontaneous report received from a contactable reporter(s) (Other HCP) from medical information team. The reporter is the patient. Other Case identifier(s): US-PFIZER INC-202101824897.  A 43 year-old female patient received bnt162b2 (BNT162B2), administered in arm right, administration date 17Dec2021 09:30 (Lot number: 3302580) at the age of 43 years as dose 3 (booster), single for covid-19 immunisation. Relevant medical history included: "Thyroid" (unspecified if ongoing), notes: Verbatim: Thyroid. Concomitant medication(s) included: METHIMAZOLE taken for thyroid disorder. Vaccination history included: Bnt162b2 (1st dose), for COVID-19 Immunization; Bnt162b2 (2nd dose), for COVID-19 Immunization. The following information was reported: IMMUNISATION (non-serious) with onset 17Dec2021 09:30, outcome "unknown", described as "Pfizer booster"; ARTHRALGIA (non-serious) with onset Dec2021, outcome "unknown", described as "have a pain shooting down my knee at this point"; AXILLARY PAIN (non-serious) with onset 17Dec2021, outcome "unknown", described as "my armpit and into like my what feels like my breast is also really painful"; PAIN IN EXTREMITY (non-serious) with onset 17Dec2021, outcome "unknown", described as "when my arm is just in rest I feel pain. When my arm is at rest and I am not moving it, I feel pain in my elbow"; DYSKINESIA (non-serious) with onset Dec2021, outcome "unknown", described as "When my arm is at rest and I am not moving it, I feel pain in my elbow". Therapeutic measures were taken as a result of arthralgia, axillary pain, pain in extremity, dyskinesia.  Additional information: Consumer (nurse) stated, We just got a booster Pfizer booster (clarified as Pfizer Covid-19 Vaccine) yesterday and her, she has had plenty of shots allergy shots (Further not clarified) her whole life. she also a nurse so she has had plenty of vaccinations intramuscularly, it's also and she thought this might be part of the immune response. she just wants to make sure that its normal. She was not having any problems like with moving her arm at all but it's pretty painful and she don't remember that the first time when she had the Pfizer shot one and two for the first vaccine." Consumer was informed that Pfizer Medical Information is the concerned department to answer the question about the role of Pfizer Drug Safety. Consumer was provided with the number of Pfizer Medical Information and was requested to select option 3, timings as 8 am to 8 pm Monday to Friday. Consumer further stated, "You cannot help me with either one of those questions than is that correct. Consumer was again informed about the role of Pfizer Drug Safety and Pfizer Medical Information. Causality: Consumer stated, it is a result of the booster shot. Consumer stated that she takes thyroid medication, and it is called Methimazole. Consumer stated that she was taking treatment with Advil and or Ibuprofen every 4-6 hours. She stated she already completed a full safety report on the phone Saturday evening, 18Dec2021. she got her booster dose of Comirnaty Friday morning, 17Dec2021 and pretty immediately began experiencing "a lot of pain in the same arm as my injection (right arm) in her armpit down to the breast area, but not at the injection site. She was asked if Pfizer has any information about this particular adverse effect in relation to Comirnaty. She also noted that she had a terrible response to the initial vaccine, but the second dose was better and asked if Pfizer will provide an option for lighter or more infrequent booster dosing in the future. She was asked if there is an option for blood titers to determine a person's level of neutralizing antibodies prior to receiving additional doses of Comirnaty in the future. She was asked if Pfizer will provide an option for lighter or more infrequent booster dosing in the future. She asked if there is an option for blood titers to determine a person's level of neutralizing antibodies prior to receiving additional doses of Comirnaty in the future. Response included that informed her that Pfizer does not have any additional information on this at this time. Advised her that Pfizer takes into account AEs reported such as hers in determining safety and efficacy of the vaccine moving forward. Thanked her for reporting AE. Referred to HCP. Response included spoke from Postvaccination SARS-CoV-2/antibody testing. Advised her that antibody testing currently available is not recommended for determining level of immunity related to vaccination and/or prior Covid-19 infection. Advised her that Pfizer does not have any recommendations on this topic. Referred to HCP.  The lot number for [BNT162B2], was not provided and will be requested during follow up.  Follow-Up (28Dec2021): Follow-up attempts are completed. No further information is expected.