Multiple sclerosis pseudo relapse; SARS-CoV-2 infection; Gait difficulty; This literature-non-study case was reported in a literature article and describes the occurrence of MULTIPLE SCLEROSIS PSEUDO RELAPSE (Multiple sclerosis pseudo relapse) in a female patient of an unknown age who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.    Concurrent medical conditions included Multiple sclerosis.   On an unknown date, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form and third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On an unknown date, the patient experienced MULTIPLE SCLEROSIS PSEUDO RELAPSE (Multiple sclerosis pseudo relapse) (seriousness criterion medically significant) and GAIT DISTURBANCE (Gait difficulty). an unknown date, the patient experienced COVID-19 (SARS-CoV-2 infection). At the time of the report, MULTIPLE SCLEROSIS PSEUDO RELAPSE (Multiple sclerosis pseudo relapse) and COVID-19 (SARS-CoV-2 infection) outcome was unknown and GAIT DISTURBANCE (Gait difficulty) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, SARS-CoV-2 test: Positive.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   Concomitant medication was not specified, however, patients included in the study were administered with B-Cell Therapies (ocrelizumab and rituximab), Alemtuzumab, S1P-modulators (fingolimod and ozanimod), Teriflunomide, Fumarates (dimethyl fumarate and diroximel fumarate), Natalizumab, Glatiramer acetate and Interferons Cladribine  No treatment medication was reported. After each vaccination, gait difficulty lasted 24 h after the first and second doses and 7 days after the booster dose. Patient reported testing positive for SARS-CoV-2 one day after her first mRNA-1273 dose with worsening fatigue that lasted approximately 12 days. Author stated that, of note, most patients reporting a pseudo-relapse returned to baseline within less than 96 h except for the 2 cases. There was no permanent neurological disability or severe, life-threatening adverse events reported. No treatment was recommended or performed during any of these pseudo-relapse cases. No acute cases of MS relapse were noted in our studied population that could be confirmed by clinical or radiological findings. The reported pseudo-relapses largely consisted of a transient resurgence of MS symptoms, including paresthesia, lower extremity weakness, dysarthria, and cognitive impairment. Author also stated that altogether, the risk of having a pseudo-relapse after receiving BNT162b2 and mRNA-1273 was low. It cannot be determined if the mRNA vaccine variants directly caused a pseudo-relapse in this MS population. Side effects from the vaccine such as fever or myalgia could temporarily provoke old symptoms similar to a systemic infection. Most cases of pseudo-relapses resolved completely within 96 h except for 2 cases that lasted for 1-2 weeks.   This case was linked to US-MODERNATX, INC.-MOD-2023-732774 (E2B Linked Report).  Company comment: This is a literature non-study case concerning a female patient of an unknown age (mean age 55.3) with Concurrent medical condition of Multiple sclerosis, who experienced the serious unexpected medically significant multiple sclerosis pseudo relapse. The event occurred after receiving a dose of mRNA-1273 vaccine (event and vaccine dates were not provided). The patient received 3 doses of the mRNA-1273 vaccine. Treatment or concomitant medication was not provided. The event was reported as resolved. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report   Most recent FOLLOW-UP information incorporated above includes: On 16-Jul-2023: Follow-up received by safety on 18-Jul-2023 has an email with abstract and contains information regarding other 2 patients On 19-Jul-2023: Follow-up received by safety on 20-Jul-2023 has an email with full text article and contains no new information.; Sender's Comments: Company comment: This is a literature non-study case concerning a female patient of an unknown age (mean age 55.3) with Concurrent medical condition of Multiple sclerosis, who experienced the serious unexpected medically significant multiple sclerosis pseudo relapse. The event occurred after receiving a dose of mRNA-1273 vaccine (event and vaccine dates were not provided). The patient received 3 doses of the mRNA-1273 vaccine. Treatment or concomitant medication was not provided. The event was reported as resolved. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report. US-MODERNATX, INC.-MOD-2023-732774:Master case