She was unable to walk; Within 4 hours, she experienced severe pain throughout her body; As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles; As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles.; As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles.; She gets muscle spasms in her calf, toes and hands; She can walk, but bending, sitting and sleeping are very difficult; This spontaneous case was reported by a patient family member or friend and describes the occurrence of BACK PAIN (As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles.), MUSCULOSKELETAL PAIN (As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles.), MUSCLE SPASMS (She gets muscle spasms in her calf, toes and hands), MOBILITY DECREASED (She can walk, but bending, sitting and sleeping are very difficult) and GAIT INABILITY (She was unable to walk) in a 78-year-old female patient who received mRNA-1273.815 (SPIKEVAX 2023-2024) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.    On 29-Sep-2023, the patient received dose of mRNA-1273.815 (SPIKEVAX 2023-2024) (unknown route) 1 dosage form. In 2023, the patient experienced BACK PAIN (As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles.), MUSCULOSKELETAL PAIN (As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles.), MUSCLE SPASMS (She gets muscle spasms in her calf, toes and hands), MOBILITY DECREASED (She can walk, but bending, sitting and sleeping are very difficult) and ARTHRALGIA (As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles). On 29-Sep-2023,  after starting mRNA-1273.815 (SPIKEVAX 2023-2024), the patient experienced GAIT INABILITY (She was unable to walk) and MYALGIA (Within 4 hours, she experienced severe pain throughout her body). The patient was treated with CORTISONE (oral use) at an unspecified dose and frequency. At the time of the report, BACK PAIN (As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles.), MUSCULOSKELETAL PAIN (As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles.), MUSCLE SPASMS (She gets muscle spasms in her calf, toes and hands), MOBILITY DECREASED (She can walk, but bending, sitting and sleeping are very difficult), ARTHRALGIA (As of today, she has severe pain in her lower back, both hips, buttocks, both knees and ankles) and MYALGIA (Within 4 hours, she experienced severe pain throughout her body) had not resolved and GAIT INABILITY (She was unable to walk) was resolving.        For mRNA-1273.815 (SPIKEVAX 2023-2024) (Unknown), the reporter did not provide any causality assessments.   No concomitant drug was reported.  Within 4 hours of Moderna vaccination, patient experienced severe pain throughout her body. She was unable to walk. As of day, of reporting, she has severe pain in her lower back, both hips, buttocks, both knees and ankles. She gets muscle spasms in her calf, toes and hands. She can walk, but bending, sitting and sleeping are very difficult. She was absolutely fine before booster. Now her quality of life was not good. Nobody really knows what to do to help her. She was given several rounds of oral cortisone which did not help her. Doctors were at a loss to help her.   Most recent FOLLOW-UP information incorporated above includes: On 20-Nov-2023: Live follow-up received: Additional reporter and reference numbers were updated.