MRI and it showed possible myelitis; Diarrhea; Hard to talk; Profound jaw fatigue; Started developing numbness and tingling in feet; Tingling in feet, then tingling in hand; Painful jaw and hard to talk.; Vomiting; Nausea; Short of breath; oxygen level down to 85%; Started feeling warm head to toe; had hot flashes from head to toe; Felt light headed; Heart rate went all the way up to 170 beats per minute / Heart rate went to 200 beats per minute at home / Heart rate went above 100 / high Heart rate which was intermittent; This spontaneous case was reported by a consumer and describes the occurrence of HYPOXIA (oxygen level down to 85%) and MYELITIS (MRI and it showed possible myelitis) in a 31-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 039K20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.    On 29-Dec-2020, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 29-Dec-2020, the patient experienced HOT FLUSH (had hot flashes from head to toe) and DIZZINESS (Felt light headed). 29-Dec-2020, the patient experienced TACHYCARDIA (Heart rate went all the way up to 170 beats per minute / Heart rate went to 200 beats per minute at home / Heart rate went above 100 / high Heart rate which was intermittent). On 31-Dec-2020, the patient experienced HYPOXIA (oxygen level down to 85%) (seriousness criterion medically significant) and FEELING HOT (Started feeling warm head to toe). On 01-Jan-2021, the patient experienced DYSPNOEA (Short of breath), VOMITING (Vomiting) and NAUSEA (Nausea). On 03-Jan-2021, the patient experienced HYPOAESTHESIA (Started developing numbness and tingling in feet), PARAESTHESIA (Tingling in feet, then tingling in hand), PAIN IN JAW (Painful jaw and hard to talk.) and JAW DISORDER (Profound jaw fatigue). On an unknown date, the patient experienced MYELITIS (MRI and it showed possible myelitis) (seriousness criterion medically significant), DIARRHOEA (Diarrhea) and DYSARTHRIA (Hard to talk). At the time of the report, HYPOXIA (oxygen level down to 85%), MYELITIS (MRI and it showed possible myelitis), HOT FLUSH (had hot flashes from head to toe), DIZZINESS (Felt light headed), FEELING HOT (Started feeling warm head to toe), DYSPNOEA (Short of breath), DIARRHOEA (Diarrhea), HYPOAESTHESIA (Started developing numbness and tingling in feet), PARAESTHESIA (Tingling in feet, then tingling in hand), PAIN IN JAW (Painful jaw and hard to talk.), DYSARTHRIA (Hard to talk), VOMITING (Vomiting), NAUSEA (Nausea) and JAW DISORDER (Profound jaw fatigue) outcome was unknown and TACHYCARDIA (Heart rate went all the way up to 170 beats per minute / Heart rate went to 200 beats per minute at home / Heart rate went above 100 / high Heart rate which was intermittent) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Heart rate: 170 beats (High) Heart rate went all the way up to 170 beats per minute, 200 beats (High) Heart rate went to 200 beats per minute at home and 100 beats (High) Heart rate went above 100. On an unknown date, Oxygen saturation: 85% (Low) oxygen levels went down to 85%.     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) was unknown.       No concomitant medications were provided. No treatment information was provided.  Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded.  Myelitis was captured as an event as per SD assessment, further information is expected to confirm event.; Sender's Comments: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded.  Myelitis was captured as an event as per SD assessment, further information is expected to confirm event.