Fever; urticaria; rash all over the body, chest, face, back and ears; Acute allergic reaction; This spontaneous case was reported by a consumer and describes the occurrence of URTICARIA (urticaria), RASH (rash all over the body, chest, face, back and ears), HYPERSENSITIVITY (Acute allergic reaction) and PYREXIA (Fever) in a 19-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 058H21A, 033C21A and 038B21A) for COVID-19 vaccination.     Concurrent medical conditions included Allergic to cats.   On 15-Apr-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 13-May-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 15-Dec-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 15-Dec-2021,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced PYREXIA (Fever). In December 2021, the patient experienced URTICARIA (urticaria), RASH (rash all over the body, chest, face, back and ears) and HYPERSENSITIVITY (Acute allergic reaction). The patient was treated with PREDNISONE for Rash, at an unspecified dose and frequency and DIPHENHYDRAMINE HYDROCHLORIDE (BENADRYL [DIPHENHYDRAMINE HYDROCHLORIDE]) for Rash all over, at an unspecified dose and frequency. On 16-Dec-2021, PYREXIA (Fever) had resolved. At the time of the report, URTICARIA (urticaria) and HYPERSENSITIVITY (Acute allergic reaction) outcome was unknown and RASH (rash all over the body, chest, face, back and ears) had not resolved.            Reporter mentioned that Patient was in the facility and was a prominent football player. He has been in great shape and good health with no health conditions, he was highly athletic, and his diet was clean, He had done some travelling, but there hasn't been any new food or new environmental factors, so the process of elimination leaves him with the vaccine to be the only thing that may have caused the rash.  After receiving treatment, It has become milder to an extent, but the rash continues to appear randomly on different parts of the body, The rash on his back and chest looked like he had poison ivy. Patient went to the ER on 29-Dec-2021 3AM, The doctor there diagnosed him with acute allergic reaction and urticaria. The rash was extreme, It got really bad and his biceps looks like he had chicken pox-looking rash. Patient was going back to college now and was trying to get back into shape, but with this rash, he can't. Patient travelled to Mexico between 25-Dec-2021 and 28-Dec-2021. The rash started when he was there, but there was no new food. No environmental factors. He was there with wealthy friends who had a very good mansion, so the caller doubted that the son developed the rash from travelling. Patient had pictures available of the rash from 04-Jan2022. Those pictures were taken after treatment, but the rash continued to reemerge.  Concomitant medications were not provided by reporter.; Sender's Comments: This case concerns a 19-year-old male patient with allergy to cats, who developed non-serious unexpected event of Urticaria, as well as non-serious expected events of Rash, Hypersensitivity and Pyrexia. The event of Pyrexia occurred during the same day when the patient had received the mRNA-1273 vaccine, as third (booster) dose. The event had resolved during the next day. The remaining reported events occurred during the same month when the patient had received the vaccine, but the exact start dates were not provided. As per case description, temporal relationship was suggestive. Treatment medications were prednisone and Benadryl. The patient also visited emergency department and it was stated that he had urticaria and allergic reaction. At the time of this report, the event of Rash was still ongoing, while the outcome of the events of Urticaria and Allergic reaction remained unknown. The re-challenge is not applicable having in mind that the events occurred following the third dose of the vaccine. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.