started having spontaneous urticarial rashes, these rashes appear to be raised erythematous linear and maculopapular wheels that are pruritic/he is still having spontaneous flare-ups of his rash; This spontaneous case was reported by an other health care professional and describes the occurrence of URTICARIA (started having spontaneous urticarial rashes, these rashes appear to be raised erythematous linear and maculopapular wheels that are pruritic/he is still having spontaneous flare-ups of his rash) in a 20-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 059A22A, 003B21A and 047B21A) for COVID-19 prophylaxis.     Concurrent medical conditions included Childhood asthma and Schizophrenia.   On 22-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 19-Apr-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In June 2022, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. In June 2022,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced URTICARIA (started having spontaneous urticarial rashes, these rashes appear to be raised erythematous linear and maculopapular wheels that are pruritic/he is still having spontaneous flare-ups of his rash). The patient was treated with METHYLPREDNISOLONE SODIUM SUCCINATE (SOLUMEDROL) (intravenous) for Urticarial rash, at a dose of 125 milligram; PREDNISONE (oral) for Urticarial rash, at a dose of 50 milligram once a day; PREDNISONE (oral) for Urticarial rash, at a dose of 40 milligram once a day; PREDNISONE (oral) for Urticarial rash, at a dose of 30 milligram once a day; DIPHENHYDRAMINE (oral) for Urticarial rash, at a dose of 25 milligram every six hours; CETIRIZINE (oral) for Urticarial rash, at a dose of 10 milligram once a day and FAMOTIDINE (oral) for Urticarial rash, at a dose of 20 milligram every twelve hours. At the time of the report, URTICARIA (started having spontaneous urticarial rashes, these rashes appear to be raised erythematous linear and maculopapular wheels that are pruritic/he is still having spontaneous flare-ups of his rash) had not resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 15-Jan-2022, SARS-CoV-2 test: (Positive) Positive.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   The patient was not taking any concomitant medications. The patient never had any rash before. Patient was healthy. Reporter stated that 1 week after receiving booster dose, patient started having spontaneous urticarial rashes. They were present daily in random areas throughout his body and are minimally responsive to treatment. The patient was seen at urgent care on 27-Jun-2022. The reported stated that it had been 8 days and patient was still having spontaneous flare-ups of rash.  Reporter mentioned they had a doctors appointment in August but were trying to move it up sooner. The patient was prescribed with Prednisone 50mg for 5 days, then it was tapered to 40mg for 3 days, then 30mg for 3 days, then 20mg PO q 24hs for 3 days, then 10mg PO q 24hs for 3 days.   This case was linked to MOD-2022-600695 (Patient Link).