now can't rest her arm down and she is holding her arm up; she noticed in her armpit, it was like a hump; she is holding her arm up because it hurts from the pressure from swelling; it does not hurt on the left side/it was a little bit sore; developed swelling in her armpit/swelling is more on the right; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP) from medical information team. The reporter is the patient.  A 45 year-old female patient received bnt162b2 (COMIRNATY), administered in arm right, administration date 06Jan2022 13:00 (Lot number: 3302580) at the age of 45 years as dose 3 (booster), single for covid-19 immunisation. The patient's relevant medical history was not reported. There were no concomitant medications. Vaccination history included: Bnt162b2 (Dose:1, Lot: EL8732), administration date: 02Apr2021, when the patient was 44 years old, for COVID-19 Immunization; Bnt162b2 (Dose:2, Lot: EW0150), administration date: 23Apr2021, when the patient was 44 years old, for COVID-19 Immunization. The following information was reported: SWELLING (non-serious), AXILLARY PAIN (non-serious) all with onset 07Jan2022, outcome "not recovered" and all described as "developed swelling in her armpit/swelling was more on the right which was the side she got the injection, she has slight swelling in left armpit but it does not hurt on the left side/it was a little bit sore"; JOINT RANGE OF MOTION DECREASED (non-serious), PAIN IN EXTREMITY (non-serious) all with onset 08Jan2022, outcome "not recovered" and all described as "now can't rest her arm down and she was holding her arm up because it hurts from the pressure from swelling"; AXILLARY MASS (non-serious) with onset 08Jan2022, outcome "not recovered", described as "she noticed in her armpit, it was like a hump". Therapeutic measures were taken as a result of swelling, joint range of motion decreased, axillary pain, axillary mass, pain in extremity.  Additional information included: The patient was told to call from the pharmacist. She was calling about the covid 19 vaccine. She was experiencing swelling under her armpit, states it was closer to the rib cage area near the breast. The pharmacist had not heard of that symptom. Reports the swelling was more on the right which was the side she got the injection, she had slight swelling in left armpit but it does not hurt on the left side. This was her booster dose. She was wondering if she could go exercise or if she should lay low. The patient started to notice the swelling in her armpit on Friday evening. The patient treated with ibuprofen. Outcome included It got more swollen, and then now its better. Clarifies Friday evening it was a little bit sore. It was more noticeable Saturday. Friday she laid low. Saturday when she went to scrub in the shower, she noticed in her armpit, it was like a hump. She could not rest her arm down, she was holding her arm since it hurts from the pressure. Clarifies outcome as persisting. Adverse Event (AE) Details included she was experiencing swelling under her armpit, states it was closer to the rib cage area near the breast. Reports the swelling was more on the right which was the side she got the injection, she had slight swelling in left armpit but it does not hurt on the left side. No prior vaccinations (within 4 weeks) followed by AE.  Follow-up attempts are completed. No further information is expected.