took the day off as he could not go to work; little balls on his head started with his left side of his neck and has been spreading on the back of his head   / has little balls all up and down his neck now; circular soft mushy things behind his head that has been forming/doesn't want to use the term "tumor", but it is something like that/found one behind his right ear/has little balls all up and down his neck now/little balls on his head started w; left side of his neck is swollen specifically his lymph nodes / found one behind his right ear; This spontaneous case was reported by a consumer and describes the occurrence of IMPAIRED WORK ABILITY (took the day off as he could not go to work), NECK MASS (little balls on his head started with his left side of his neck and has been spreading on the back of his head   / has little balls all up and down his neck now), MASS (circular soft mushy things behind his head that has been forming/doesn't want to use the term "tumor", but it is something like that/found one behind his right ear/has little balls all up and down his neck now/little balls on his head started with hi) and LYMPHADENOPATHY (left side of his neck is swollen specifically his lymph nodes / found one behind his right ear) in a 44-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 033C21A and 050C21A) for COVID-19 vaccination.     No Medical History information was reported.   On 12-May-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 09-Jun-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On an unknown date, the patient experienced IMPAIRED WORK ABILITY (took the day off as he could not go to work), NECK MASS (little balls on his head started with his left side of his neck and has been spreading on the back of his head   / has little balls all up and down his neck now), MASS (circular soft mushy things behind his head that has been forming/doesn't want to use the term "tumor", but it is something like that/found one behind his right ear/has little balls all up and down his neck now/little balls on his head started with hi) and LYMPHADENOPATHY (left side of his neck is swollen specifically his lymph nodes / found one behind his right ear). The patient was treated with CEPHALEXIN [CEFALEXIN] for Adverse event, at a dose of 500 mg every six hours. At the time of the report, IMPAIRED WORK ABILITY (took the day off as he could not go to work), NECK MASS (little balls on his head started with his left side of his neck and has been spreading on the back of his head   / has little balls all up and down his neck now), MASS (circular soft mushy things behind his head that has been forming/doesn't want to use the term "tumor", but it is something like that/found one behind his right ear/has little balls all up and down his neck now/little balls on his head started with hi) and LYMPHADENOPATHY (left side of his neck is swollen specifically his lymph nodes / found one behind his right ear) outcome was unknown.            Concomitant medication information not provided. The side effects were "nothing that wasn't expected".    This case was linked to MOD-2021-269788 (Patient Link).