Massive Cervical Lymphadenopathy; intermittent low-grade fever (99.9°F); fatigue; Myalgia; left neck swelling; Dysphagia; This literature-non-study case was reported in a literature article and describes the occurrence of LYMPHADENOPATHY (Massive Cervical Lymphadenopathy), PYREXIA (intermittent low-grade fever (99.9°F)), FATIGUE (fatigue), MYALGIA (Myalgia), SWELLING (left neck swelling) and DYSPHAGIA (Dysphagia) in a 58-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.   Concurrent medical conditions included Hypertension.    On an unknown date, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, the patient experienced LYMPHADENOPATHY (Massive Cervical Lymphadenopathy) (seriousness criterion hospitalization), PYREXIA (intermittent low-grade fever (99.9°F)) (seriousness criterion hospitalization prolonged), FATIGUE (fatigue) (seriousness criterion hospitalization prolonged), MYALGIA (Myalgia) (seriousness criterion hospitalization prolonged), SWELLING (left neck swelling) (seriousness criterion hospitalization prolonged) and DYSPHAGIA (Dysphagia) (seriousness criterion hospitalization prolonged). The patient was treated with PIPERACILLIN SODIUM, TAZOBACTAM SODIUM (PIPERACILLIN/TAZOBACTAM) (intravenous) for Prophylaxis, at an unspecified dose and frequency and DEXAMETHASONE (intravenous) for Lymphadenopathy cervical, at an unspecified dose and frequency. At the time of the report, LYMPHADENOPATHY (Massive Cervical Lymphadenopathy), PYREXIA (intermittent low-grade fever (99.9°F)), FATIGUE (fatigue), MYALGIA (Myalgia), SWELLING (left neck swelling) and DYSPHAGIA (Dysphagia) had resolved. Possible    DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Biopsy: abnormal (abnormal) Ultrasound-guided biopsy of the left neck lymph node was done; pathology was negative for malignancy and positive for inflammatory cells.. On an unknown date, Blood culture: negative (Negative) Negative. On an unknown date, Body temperature: 99.9°f 99.9°F. On an unknown date, C-reactive protein: 5.6 mg/dl 5.6 mg/dL. On an unknown date, Computerised tomogram: abnormal (abnormal) Computed tomography (CT) scan of the neck showed marked irregular thickening and inflammation of the sternocleidomastoid area with adjacent swelling on the left side of the neck, measuring 5.9 cm × 3.7 cm × 1.8 cm and normal (normal) Repeat CT scan of the neck on the second day of admission showed significantly decreased left neck mass swelling.. On an unknown date, Endoscopy: normal (normal) No laryngeal lesions were observed with flexible fiberoptic laryngeal endoscopy. On an unknown date, Full blood count: normal (normal) Normal. On an unknown date, HIV test: negative (Negative) Negative. On an unknown date, Physical examination: abnormal (abnormal) patient had an approximately 5.0 cm × 3.0 cm large, firm, and tender areas of edema along the left mandible and extending over the left neck. There was no pharyngeal erythema, oral ulceration, exudate, or rash. No laryngeal lesions were observed with flexible fiberoptic laryngeal endoscopy.. On an unknown date, Procalcitonin: normal (normal) Normal. On an unknown date, Red blood cell sedimentation rate: 84 mm/hr 84 mm/hr. On an unknown date, Respiratory viral panel: negative (Negative) Negative. On an unknown date, SARS-CoV-2 test: negative (Negative) Negative. On an unknown date, Streptococcus test: negative (Negative) Negative. On an unknown date, Ultrasound scan: abnormal (abnormal) Ultrasound of the neck was positive for large mass, causing mass effect upon the left internal jugular vein..     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) was unknown.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered LYMPHADENOPATHY (Massive Cervical Lymphadenopathy), PYREXIA (intermittent low-grade fever (99.9°F)), FATIGUE (fatigue), MYALGIA (Myalgia), SWELLING (left neck swelling) and DYSPHAGIA (Dysphagia) to be possibly related.    Concomitant medications were not reported.  Patient  was admitted to the hospital with lowgrade fever, fatigue, myalgia, left neck swelling, and dysphagia for 2 weeks prior to admission. During the hospitalization, he had intermittent low-grade fever (99.9°F).  Symptoms improved with resolution of fevers, diminished left neck swelling, and resolution of dysphagia. The patient was then discharged home in stable condition. During a follow-up telephone interview 2 weeks later, the patient reported no residual symptoms.  Company Comment: This case concerns a 58 year-old male patient with no relevant medical history, who experienced the unexpected serious events of left neck swelling, fever, fatigue, myalgia, dysphagia, and massive cervical lymphadenopathy. Extensive workup did not reveal alternative etiology for lymphadenopathy. The events occurred 2 days after the first dose of mRNA-1273 vaccine. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 13-Oct-2021: Follow up received by safety on 13-Oct-2021 included an Email received from a regulatory team and does not contain any new information.; Sender's Comments: This case concerns a 58 year-old male patient with no relevant medical history, who experienced the unexpected serious events of left neck swelling, fever, fatigue, myalgia, dysphagia, and massive cervical lymphadenopathy. Extensive workup did not reveal alternative etiology for lymphadenopathy. The events occurred 2 days after the first dose of mRNA-1273 vaccine. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.