Anaphylactic shock; This spontaneous case was reported by a consumer and describes the occurrence of ANAPHYLACTIC SHOCK (Anaphylactic shock) in a 41-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 019F21A) for COVID-19 vaccination.     No medical history was provided by the reporter.    On 25-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 22-Apr-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 09-Dec-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 17-Dec-2021,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced ANAPHYLACTIC SHOCK (Anaphylactic shock) (seriousness criteria hospitalization and medically significant). The patient was treated with CETIRIZINE HYDROCHLORIDE (ZYRTEC [CETIRIZINE HYDROCHLORIDE]) ongoing since an unknown date for Anaphylactic shock, at a dose of UNK UNK, qd; DIPHENHYDRAMINE HYDROCHLORIDE (BENADRYL [DIPHENHYDRAMINE HYDROCHLORIDE]) ongoing since an unknown date for Anaphylactic shock, at an unspecified dose and frequency and DEXAMETHASONE for Anaphylactic shock, at an unspecified dose and frequency. At the time of the report, ANAPHYLACTIC SHOCK (Anaphylactic shock) had not resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Echocardiogram: inconclusive (Inconclusive) Results not provided. On an unknown date, Electrocardiogram: inconclusive (Inconclusive) Results not provided.         No concomitant medications were reported.  On 17-Dec-2021 patient experienced a severe allergic reaction, symptoms described were as follows: extreme hives, palpitations, extreme muscle pain, patient was unable to move her torso and arms, swelling, hard time breathing, difficulty swallowing, and chest pain and because of this visited ER 3 times, first time was on 19-Dec-2021, second and third was both on 21-Dec-2021, because symptoms got worse. At this point, doctors administered Dexamethasone and Benadryl, because they told patient that it was an anaphylactic shock. Patient remained hospitalized for 2 nights, until 23-Dec-2021, due to symptoms were still ongoing, patient was still under treatment, taking Zyrtrec 1 per day, and Benadryl as needed. The patient's symptoms started at evening of 17-Dec-2021, and gradually got worst until 3rd visit to ER It was reported that anaphylactic shock was determined as the cause of symptoms.  Company comment: This case concerns a 41-year-old female patient with no medical history provided who experienced serious unexpected event of Anaphylactic shock. The event occurred eight days after the booster dose of mRNA-1273. It was reported that the patient experienced extreme hives, palpitations, extreme muscle pain, patient was unable to move her torso and arms, swelling, hard time breathing, difficulty swallowing, and chest pain and was diagnosed with Anaphylactic shock. The patient was hospitalized for two days, however, details regarding hospitalization were not provided. Echocardiogram and ECG were performed, however, the results were not provided. The patient was treated with Dexamethasone, Cetirizine hydrochloride and Diphenhydramine hydrochloride. At the time of the report, the event was still ongoing. No further information was provided. The benefit-risk relationship of mRNA-1273 is not affected by this report.   This case was linked to MOD-2022-437773 (Patient Link).; Sender's Comments: This case concerns a 41-year-old female patient with no medical history provided who experienced serious unexpected event of Anaphylactic shock. The event occurred eight days after the booster dose of mRNA-1273. It was reported that the patient experienced extreme hives, palpitations, extreme muscle pain, patient was unable to move her torso and arms, swelling, hard time breathing, difficulty swallowing, and chest pain and was diagnosed with Anaphylactic shock. The patient was hospitalized for two days, however, details regarding hospitalization were not provided. Echocardiogram and ECG were performed, however, the results were not provided. The patient was treated with Dexamethasone, Cetirizine hydrochloride and Diphenhydramine hydrochloride. At the time of the report, the event was still ongoing. No further information was provided. The benefit-risk relationship of mRNA-1273 is not affected by this report.