My left arm pit became very sore and swollen after my 3rd Pfizer shot booster/they told me it was my lymph nodes/swelling and pain under arm area; My left arm pit became very sore and swollen after my 3rd Pfizer shot booster/they told me it was my lymph nodes/swelling and pain under arm area; My left arm pit became very sore and swollen after my 3rd Pfizer shot booster/they told me it was my lymph nodes/swelling and pain under arm area; after my 3rd Pfizer shot booster; after my 3rd Pfizer shot booster; This is a spontaneous report from a contactable consumer (Patient). A 53-year-old non pregnant female consumer received booster dose of bnt162b2 (Pfizer BioNTech Covid-19 Vaccine, solution for injection, Batch Number/Lot Number: 30145BA Expiration date: Nov2021) via intramuscularly, administered in Arm Left (at the age of 53-years-old), administered on 23Sep2021 at 2:00 PM as DOSE 3 (BOOSTER), SINGLE for covid-19 immunization. The medical history included rheumatoid arthritis from 2007 and ongoing, Sjogren's syndrome from 2010 and ongoing, MGUS from 2010 and ongoing. Concomitant medications included rosuvastatin (10mg) taken High cholesterol from an unspecified start date and ongoing; losartan (25mg) taken for High Blood pressure from an unspecified start date and ongoing; gabapentin taken for an unspecified indication, start and stop date were not reported; Tylenol taken for Arthritis Pain from an unspecified start date and ongoing; Prilosec (20 mg)taken for reflux disease from an unspecified start date and ongoing and multi vitamin taken for an unspecified indication, start and stop date were not reported. Historical vaccines includes received first dose of bnt162b2 (Pfizer BioNTech Covid-19 Vaccine, solution for injection, Batch Number/Lot Number: EN6206) via intramuscularly, administered in Arm Left (at the age of 53-years-old), administered on 04Mar2021 at 2.00 PM as dose 1, single and also received second dose of bnt162b2 (Pfizer BioNTech Covid-19 Vaccine, solution for injection, Batch Number/Lot Number: ER2613) via intramuscularly, administered in Arm Left (at the age of 53-years-old), administered on 25Mar2021 as dose 2, single for covid-19 immunization. The patient was not pregnant at time of vaccination. On 24Sep2021 at 06:00 AM patient experienced left arm pit became very sore and swollen after 3rd Pfizer shot booster/they told me it was my lymph nodes/swelling and pain under arm area. Patient was not having no known allergies. The patient underwent lab tests and procedures which included HLAB27 marker in 2007 with unknown results. Treatment was provided with Tylenol and ice packs. The outcome for the events experienced left arm pit became very sore and swollen after 3rd Pfizer shot booster/they told me it was my lymph nodes/swelling and pain under arm area was recovered.  Follow-up (13Oct2021): This is a follow-up spontaneous report from a contactable consumer included: historical vaccines details, relevant medical history details, Booster dose details updated lot and expiration date added, past drugs events details, concomitant drugs details, treatment updated, outcome of the event updated, clinical information updated.  No follow-up attempts are possible. No further information is expected.