Heart was fluttering; heart beating harder than normal after 4 hours but lasting 1 hour only/She could feel her heart beating with the third shot/Heart beating faster than normal; She felt weak. After an hour she felt good again; cold all night/could not get warm no matter what/Feet were ice cold; Goosebumps; Booster stung for 2 hours after getting it/Each shot hurt a little bit more; Slight headache; This spontaneous case was reported by a consumer and describes the occurrence of CARDIAC FLUTTER (Heart was fluttering), HEART RATE INCREASED (heart beating harder than normal after 4 hours but lasting 1 hour only/She could feel her heart beating with the third shot/Heart beating faster than normal), ASTHENIA (She felt weak. After an hour she felt good again), FEELING COLD (cold all night/could not get warm no matter what/Feet were ice cold) and PILOERECTION (Goosebumps) in a 78-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No medical history was provided by the reporter.  Concomitant products included HYDROCHLOROTHIAZIDE and LEVOTHYROXINE for an unknown indication.   On 22-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 19-Feb-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 01-Dec-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 01-Dec-2021, the patient experienced CARDIAC FLUTTER (Heart was fluttering), HEART RATE INCREASED (heart beating harder than normal after 4 hours but lasting 1 hour only/She could feel her heart beating with the third shot/Heart beating faster than normal), ASTHENIA (She felt weak. After an hour she felt good again), FEELING COLD (cold all night/could not get warm no matter what/Feet were ice cold), PILOERECTION (Goosebumps), VACCINATION SITE PAIN (Booster stung for 2 hours after getting it/Each shot hurt a little bit more) and HEADACHE (Slight headache). On 01-Dec-2021, CARDIAC FLUTTER (Heart was fluttering), HEART RATE INCREASED (heart beating harder than normal after 4 hours but lasting 1 hour only/She could feel her heart beating with the third shot/Heart beating faster than normal), ASTHENIA (She felt weak. After an hour she felt good again) and VACCINATION SITE PAIN (Booster stung for 2 hours after getting it/Each shot hurt a little bit more) had resolved. At the time of the report, FEELING COLD (cold all night/could not get warm no matter what/Feet were ice cold), PILOERECTION (Goosebumps) and HEADACHE (Slight headache) outcome was unknown.            No treatment medication was provided.  Patient could feel her heart beating with the third shot. It made her feel like she is on the verge of pre-diabetic which she is not.  Company comment: This is a spontaneous case concerning a 78 year-old, female patient with concomitant use of hydrochlorothiazide and levothyroxine, who experienced the non-serious unexpected, according CCDS, AESI of cardiac flutter. The event occurred approximately 4 hours after the booster dose of mRNA-1273 vaccine and lasted one hour. No treatment was reported for the adverse event. The rechallenge was not applicable, as the events were reported exclusively after the booster dose. The concomitant use of hydrochlorothiazide and levothyroxine remain as confounders. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.   This case was linked to MOD-2021-403833 (Patient Link).; Sender's Comments: This is a spontaneous case concerning a 78 year-old, female patient with concomitant use of hydrochlorothiazide and levothyroxine, who experienced the non-serious unexpected, according CCDS, AESI of cardiac flutter. The event occurred approximately 4 hours after the booster dose of mRNA-1273 vaccine and lasted one hour. No treatment was reported for the adverse event. The rechallenge was not applicable, as the events were reported exclusively after the booster dose. The concomitant use of hydrochlorothiazide and levothyroxine remain as confounders. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.