On day two, I woke up and saw that my lymph node under my left armpit swelled up to the size of a grapefruit and it was quite painful; On day two, I woke up and saw that my lymph node under my left armpit swelled up to the size of a grapefruit and it was quite painful/ but exercise still caused pain in the armpit for an additonal 3-4 days.; It hurt to even put my arm down; In addition, I had bad mid-back pain.; Dose number: 3; This is a spontaneous report from a contactable reporter (consumer or other non HCP). The reporter is the patient.  A 45-year-old female patient (not pregnant) received bnt162b2 (BNT162B2), administered in left arm, administration date 27Dec2021 at 17:15 (Lot number: 33130BA) at the age of 45 years as dose 3 (booster), single for COVID-19 immunisation. The patient had no relevant medical history. Concomitant medication included: MIRENA IUD. Vaccination history included: Bnt162b2 (DOSE 1, SINGLE; Lot Number:ER8737; Anatomical location: Left Arm; Administration time: 17:30), administration date: 01Apr2021, when the patient was 44 years old, for COVID-19 immunisation and Bnt162b2 (DOSE 2, SINGLE; Lot Number:ER8731; Anatomical location: Left Arm; Administration time: 17:15), administration date: 22Apr2021, when the patient was 44 years old, for COVID-19 immunisation.  The following information was reported: IMMUNISATION (non-serious) with onset 27Dec2021 at 17:15, outcome "unknown", described as "Dose number: 3"; LYMPHADENOPATHY (non-serious) with onset 29Dec2021 at 06:00, outcome "recovered" (an unknown date in Jan2022), described as "On day two, I woke up and saw that my lymph node under my left armpit swelled up to the size of a grapefruit and it was quite painful"; LYMPH NODE PAIN (non-serious) with onset 29Dec2021 at 06:00, outcome "recovered" (an unknown date in Jan2022), described as "On day two, I woke up and saw that my lymph node under my left armpit swelled up to the size of a grapefruit and it was quite painful/ but exercise still caused pain in the armpit for an additonal 3-4 days"; PAIN (non-serious) with onset 29Dec2021 at 06:00, outcome "recovered" (an unknown date in Jan2022), described as "It hurt to even put my arm down"; BACK PAIN (non-serious) with onset 29Dec2021 at 06:00, outcome "recovered" (an unknown date in Jan2022), described as "In addition, I had bad mid-back pain". Therapeutic measures were taken as a result of lymphadenopathy, lymph node pain, pain and back pain.  Additional Information: The patient had no known allergies. The patient did not receive any other vaccines within four weeks prior to the prior to the COVID vaccine. Prior to vaccination, the patient was not diagnosed with COVID-19. The patient reported that it lasted about 5 days for the back pain and 6-7 days for the swelling and armpit pain. After a week, the swelling and pain went down enough to wear a bra again but exercise still caused pain in the armpit for an additional 3-4 days. At the time of report, it was back to normal. Since the vaccination, the patient had not been tested for COVID-19. The events did not result in doctor or other healthcare professional office/clinic visit and emergency room/department or urgent care. Treatment taken as a result of lymphadenopathy, lymph node pain, pain and back pain included hot compresses and massaging the area.