lost all potassium after her second dose; sore arm; This case was received via an unknown source (no reference has been entered for a health authority or license partner) on 06-Apr-2022 and was forwarded to Moderna on 06-Apr-2022.    This spontaneous case was reported by a consumer and describes the occurrence of HYPOKALAEMIA (lost all potassium after her second dose) in a 52-year-old female patient who received mRNA-1273 (Spikevax) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Primary immunodeficiency syndrome (history of primary and secondary immune deficiency. She was born with it but the condition was not diagnosed until 14 years ago.) and Secondary immunodeficiency (history of primary and secondary immune deficiency. She was born with it but the condition was not diagnosed until 14 years ago.). Concomitant products included IMMUNOGLOBULINS NOS (IMMUNOGLOBULIN I.V) for Primary immunodeficiency syndrome and Secondary immunodeficiency, ESOMEPRAZOLE SODIUM (NEXIUM [ESOMEPRAZOLE SODIUM]), GABAPENTIN, NORTRIPTYLINE, POTASSIUM, CYANOCOBALAMIN (B12 [CYANOCOBALAMIN]), MAGNESIUM, ELDERBERRY [SAMBUCUS NIGRA] and MULTIVITAMINS [VITAMINS NOS] for an unknown indication.   On an unknown date, the patient received second dose of mRNA-1273 (Spikevax) (unknown route) .5 milliliter. On an unknown date, received first dose of mRNA-1273 (Spikevax) (unknown route) dosage was changed to .5 milliliter. On an unknown date, the patient experienced HYPOKALAEMIA (lost all potassium after her second dose) (seriousness criterion medically significant) and PAIN IN EXTREMITY (sore arm). At the time of the report, HYPOKALAEMIA (lost all potassium after her second dose) had resolved with sequelae and PAIN IN EXTREMITY (sore arm) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Antibody test: positive (Positive) positive. On an unknown date, Blood potassium: low (Low) Low.         It was reported patient received IVIg treatments for her medical condition (primary and secondary immune deficiency) every 3 weeks and Multvitamins. Due to the fact that she received IVIg treatments for her condition, four doctors told her not to receive any COVID-19 vaccines. The patient went ahead and received 2 doses of Moderna COVID-19 vaccine. She had a sore arm for one day after receiving the second dose of the vaccine. She did not experience any other side effects. She recently got an antibody test done to see if the Moderna vaccine was effective for her with her IVIg treatments and it came back positive. In between her two doses of the Moderna COVID-19 vaccines, she stopped her IVIg treatment which made her extremely ill. Since then, she had resumed her treatments again in the fear of getting sick. Allergies were unknown and covid positive test was unknown. There was no improvement or worsening, but the patient mentioned that her potassium levels had gone down significantly since she had received the second dose of the Moderna vaccine. The AEs did not cause the patient to seek any medical care (office visit, urgent care, ER, and hospitalization). No treatment information has been provided for the events.  This is a spontaneous case concerning a 52-year-old female patient with a medical history of primary immunodeficiency syndrome and secondary immunodeficiency, who experienced the unexpected event of hypokalaemia and the expected event of pain in extremity. The events and the first and second dose of mRNA  1273 vaccine was experienced on an unknown date. Hypokalaemia, a medically significant event resolved by the time of this report but with sequelae. The reporter's assessment was not provided. The benefit-risk relationship of the vaccine is not affected by this report.   This case was linked to MOD-2022-533793 (Patient Link).; Sender's Comments: This is a spontaneous case concerning a 52-year-old female patient with a medical history of primary immunodeficiency syndrome and secondary immunodeficiency, who experienced the unexpected event of hypokalaemia and the expected event of pain in extremity. The events and the first and second dose of mRNA  1273 vaccine was experienced on an unknown date. Hypokalaemia, a medically significant event resolved by the time of this report but with sequelae. The reporter's assessment was not provided. The benefit-risk relationship of the vaccine is not affected by this report.