extremely difficult for him to walk; The muscles just froze out/muscles to seize up; He had friends change his bedding, take the trash out, shop all winter; couldn't drive; very fatiguing/extreme fatigue; he doesn't have pain when he's sitting. It happens when he tries to walk; muscles are so cramped up/muscles will get jerky; concerned, worried, and terrified; feels helpless; muscles weren't working right. They were fatigued; next day they couldn't walk , are basically 90% crippled from the booster shot/could walk around his room, but not easily/crippled for the rest of my life/could be permanent; got their booster the next day they felt very weak in their legs/legs were just really weak/ legs are so weak/no strength in my legs/muscles are getting weaker; really weak,He had no strength in his legs; This spontaneous case was reported by a patient and describes the occurrence of GAIT INABILITY (next day they couldn't walk , are basically 90% crippled from the booster shot/could walk around his room, but not easily/crippled for the rest of my life/could be permanent), GAIT DISTURBANCE (extremely difficult for him to walk), MUSCULAR WEAKNESS (got their booster the next day they felt very weak in their legs/legs were just really weak/ legs are so weak/no strength in my legs/muscles are getting weaker), MUSCULOSKELETAL STIFFNESS (The muscles just froze out/muscles to seize up) and MUSCLE FATIGUE (muscles weren't working right. They were fatigued) in a 74-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 91F21A, 044A21A and 003A21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Patient never tested or diagnosed positive for COVID. Patient did not receive other vaccines within 1 month prior to Moderna COVID-19 vaccine.  Concurrent medical conditions included Drug allergy (Suboxone allergy) and Bronchitis (comes and goes).   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 12-Dec-2021, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 13-Dec-2021, the patient experienced MUSCULAR WEAKNESS (got their booster the next day they felt very weak in their legs/legs were just really weak/ legs are so weak/no strength in my legs/muscles are getting weaker) and ASTHENIA (really weak,He had no strength in his legs). On 14-Dec-2021, the patient experienced GAIT INABILITY (next day they couldn't walk , are basically 90% crippled from the booster shot/could walk around his room, but not easily/crippled for the rest of my life/could be permanent) and MUSCLE FATIGUE (muscles weren't working right. They were fatigued). On 23-May-2022, the patient experienced MUSCLE SPASMS (muscles are so cramped up/muscles will get jerky), ANXIETY (concerned, worried, and terrified) and HELPLESSNESS (feels helpless). On an unknown date, the patient experienced GAIT DISTURBANCE (extremely difficult for him to walk), MUSCULOSKELETAL STIFFNESS (The muscles just froze out/muscles to seize up), LOSS OF PERSONAL INDEPENDENCE IN DAILY ACTIVITIES (He had friends change his bedding, take the trash out, shop all winter), IMPAIRED DRIVING ABILITY (couldn't drive), FATIGUE (very fatiguing/extreme fatigue) and PAIN IN EXTREMITY (he doesn't have pain when he's sitting. It happens when he tries to walk). The patient was treated with Physical therapy (tried physical therapy because his doctor recommended it. It worked for a couple of weeks) for Muscular weakness. At the time of the report, GAIT INABILITY (next day they couldn't walk , are basically 90% crippled from the booster shot/could walk around his room, but not easily/crippled for the rest of my life/could be permanent) and GAIT DISTURBANCE (extremely difficult for him to walk) had not resolved and MUSCULAR WEAKNESS (got their booster the next day they felt very weak in their legs/legs were just really weak/ legs are so weak/no strength in my legs/muscles are getting weaker), MUSCULOSKELETAL STIFFNESS (The muscles just froze out/muscles to seize up), MUSCLE FATIGUE (muscles weren't working right. They were fatigued), LOSS OF PERSONAL INDEPENDENCE IN DAILY ACTIVITIES (He had friends change his bedding, take the trash out, shop all winter), IMPAIRED DRIVING ABILITY (couldn't drive), ASTHENIA (really weak,He had no strength in his legs), MUSCLE SPASMS (muscles are so cramped up/muscles will get jerky), ANXIETY (concerned, worried, and terrified), HELPLESSNESS (feels helpless), FATIGUE (very fatiguing/extreme fatigue) and PAIN IN EXTREMITY (he doesn't have pain when he's sitting. It happens when he tries to walk) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Blood creatine phosphokinase: normal (normal) was fine.         The patient received first two vaccines and there was no problem. The day before getting the booster, patient was walking fine. The patient got booster shot late in the day and next morning was really weak, legs were really weak. By the next morning, the patient couldn't walk. could walk across the room. The muscles weren't working right. They were fatigued. Patient went to doctor, who told it was an adverse reaction that would go away but it was not went away. Patient visited 4 doctors, including a neurologist. They did not have a way to test what was actually happening, no way of doing a diagnosis or treatment. Patient lived with this for the last 6 months. The patient would be crippled for the rest of life, but did not wanted to. The patient wanted to know why the booster caused muscles to seized up. When the patient used exercise bike, it was very fatiguing. The patient realized that this was not temporary and could be permanent. On 23-May-2022, patient's legs were so weak. The patient was supposed to get groceries but muscles were so cramped up. Patient felt like aged so much. It was getting worse than when it first happened. Patient did not believe it was Guillain Barre syndrome. Patient's doctor thought it was a statin, so he was off cholesterol medicines for two months. However, Creatine kinase level was fine and doctor determined it was not from the statin.  The patient tried physical therapy and it worked for a couple of weeks but then muscles got so fatigued, could not do anything. Patient did not take any medications/treatment for symptoms.   Most recent FOLLOW-UP information incorporated above includes: On 23-May-2022: Significant live follow up contains reporter details (first name updated, address and contact details), patient demographics, medical history, allergies, suspect information, lab details and new events added. On 23-May-2022: Live follow-up contains non significant information. Reporters email ID was corrected.