Pressure pain in lower abdomen, inflammation pain in midsection; Pressure pain in lower abdomen, inflammation pain in midsection; stomach muscles felt weak; Patient recieved 2nd booster dose of 0.5ml instead of 0.25ml; This spontaneous case was reported by a patient and describes the occurrence of ABDOMINAL PAIN LOWER (Pressure pain in lower abdomen, inflammation pain in midsection), INFLAMMATORY PAIN (Pressure pain in lower abdomen, inflammation pain in midsection), MUSCULAR WEAKNESS (stomach muscles felt weak) and ACCIDENTAL OVERDOSE (Patient recieved 2nd booster dose of 0.5ml instead of 0.25ml) in a 54-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 058A22-2A) for COVID-19 prophylaxis.     The patient's past medical history included Diverticulitis (1 episode) in August 2019. Previously administered products included for Product used for unknown indication: JANSSEN (1st dose). Past adverse reactions to the above products included No adverse event with JANSSEN. Family history included Allergic reaction to antibiotics (family history of allergy to Ciprofloxacin.) since an unknown date and Allergic reaction to antibiotics (family history of allergy to fluoroquinolones) since an unknown date. Concurrent medical conditions included Blood pressure high (mild), Nonalcoholic fatty liver disease, Obesity, Klippel-Feil syndrome (congenital malformation of spine), Sleep apnea, Sulfonamide allergy (sulfa allergy), Food allergen sensitization (food sensitivities to wheat), Milk allergy (food sensitivities to milk/cream) and Food allergy (food sensitivities to some soya).   On 03-Jun-2022, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On an unknown date, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 03-Jun-2022, the patient experienced ABDOMINAL PAIN LOWER (Pressure pain in lower abdomen, inflammation pain in midsection), INFLAMMATORY PAIN (Pressure pain in lower abdomen, inflammation pain in midsection), MUSCULAR WEAKNESS (stomach muscles felt weak) and ACCIDENTAL OVERDOSE (Patient recieved 2nd booster dose of 0.5ml instead of 0.25ml). The patient was treated with DOCUSATE SODIUM (STOOL SOFTENER) from 03-Jun-2022 to 04-Jun-2022 for Abdominal discomfort, at an unspecified dose and frequency; PLANTAGO OVATA (METAMUCIL [PLANTAGO OVATA]) from 03-Jun-2022 to 04-Jun-2022 for Abdominal discomfort, at an unspecified dose and frequency; MAGNESIUM for Abdominal discomfort, at an unspecified dose and frequency and ZINC for Abdominal discomfort, at an unspecified dose and frequency. On 05-Jun-2022, ABDOMINAL PAIN LOWER (Pressure pain in lower abdomen, inflammation pain in midsection), INFLAMMATORY PAIN (Pressure pain in lower abdomen, inflammation pain in midsection) and MUSCULAR WEAKNESS (stomach muscles felt weak) had resolved with sequelae. At the time of the report, ACCIDENTAL OVERDOSE (Patient received 2nd booster dose of 0.5ml instead of 0.25ml) outcome was unknown. No concomitant drug reported. Patient thought it may have been a flare up of diverticulitis at first. Patient took stool softener and fiber supplement that night and next morning and laid down but couldn't get comfortable. Felt like it might help to eliminate. Patient walked bent over. Next day entire midsection felt swollen, uncomfortable to try to bend or sit, stomach muscles felt weak. Patient took magnesium, zinc later in the day to see if it would help. It seemed to gradually ease in waves and was nearly gone by Sunday with just a bit of wave of pressure for periods but was not feeling myself the rest of that day.