Multiple sclerosis pseudo-relapse; SARS-CoV-2 Infection; 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. Concomitant products included OCRELIZUMAB for an unknown indication.   On an unknown date, the patient received third 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 first 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 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) 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.   This case belongs to patient no 8 of 8 patients reported.  treatment medications were not reported.  Author retrospectively identified 250 Multiple sclerosis (MS) patients at institution who had received the initial vaccination cycle of the currently approved COVID-19 vaccines in the country. 151 of these patients also received a booster dose. Side effects (SE) attributed to the COVID-19 vaccinations during a 90- day post-vaccination observation period were collected as part of the standard clinical care.  Pseudo-relapse following more than one vaccination event was reported by only one other patient who received the mRNA-1273 vaccine. Each time, patient experienced gait difficulty which lasted 24 hours after the first and second doses and 7 days after the booster dose. Patient reported testing positive for SARS-CoV-2 one day after the first mRNA-1273 dose with worsening fatigue that lasted approximately 12 days.  It was reported that, 70 patients received the mRNA-1273 booster dose with 2 reports of pseudo-relapse. Overall, 2% of studied mRNA-1273 population experienced pseudo-relapse symptoms following the first dose as compared to 5% after the second dose, and 3% with the booster. It was reported that, 22 patients swapped between the mRNA vaccines for their initial vaccination cycle and the booster dose.  Most patients of pseudo-relapses resolved completely within 96 h except for 2 cases that lasted for 12 weeks.  Patient experienced unilateral lower extremity weakness following the second dose of mRNA-1273 that spontaneously resolved within 96 h. There was a possibility that the patient contracted COVID-19 after their first dose due to the possible decreased immune-response for patients on B-cell therapy. Alternatively, the patient could have had asymptomatic COVID-19 prior to first dose administration. In general, we did not identify a clear correlation between a type of disease modifying therapy (DMT) and incidence of SE.   This case was linked to US-MODERNATX, INC.-MOD-2023-732774 (Linked Report).  Company comment: This is a literature non-study case concerning a female patient of an unknown age (mean age 55.3) with past medical history of Multiple sclerosis and Concomitant product of OCRELIZUMAB for an unknown indication, 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. Non serious event of SARS-CoV-2 Infection was also reported in the case. Treatment or concomitant medication was provided. Interchange of vaccine products and Revaccination with different COVID-19 vaccine were noted in the case. 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 11-Jul-2023: Live follow-up received by safety on 12-Jul-2023 has an email with full text article and contains significant information. Reporter's information, literature information, patient details, suspect details, co-suspect details and event details were updated.; 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 past medical history of Multiple sclerosis and Concomitant product of OCRELIZUMAB for an unknown indication, 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. Non serious event of SARS-CoV-2 Infection was also reported in the case. Treatment or concomitant medication was provided. Interchange of vaccine products and Revaccination with different COVID-19 vaccine were noted in the case. 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