Multiple sclerosis pseudo-relapse; Interchange of vaccine products; Revaccination with different COVID-19 vaccine; 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.      Co-suspect product included non-company product BNT162B2 for COVID-19 prophylaxis.    The patient's past medical history included Multiple sclerosis.   On an unknown date, the patient received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form and second dose of BNT162B2 (unknown route) 1 dosage form. On an unknown date, the patient experienced MULTIPLE SCLEROSIS PSEUDO RELAPSE (Multiple sclerosis pseudo-relapse) (seriousness criterion medically significant), INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and COVID-19 IMMUNISATION (Revaccination with different COVID-19 vaccine). At the time of the report, MULTIPLE SCLEROSIS PSEUDO RELAPSE (Multiple sclerosis pseudo-relapse), INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and COVID-19 IMMUNISATION (Revaccination with different COVID-19 vaccine) had resolved.        For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered MULTIPLE SCLEROSIS PSEUDO RELAPSE (Multiple sclerosis pseudo-relapse) to be related. No further causality assessments were provided for INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and COVID-19 IMMUNISATION (Revaccination with different COVID-19 vaccine).   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 Co-suspect product that included non-company product BNT162B2 for COVID-19 prophylaxis, who experienced the serious unexpected medically significant multiple sclerosis pseudo relapse. The event occurred after receiving the (third) booster dose of mRNA-1273 vaccine (event and vaccine date were not provided). The patient received 2nd dose of the BNT162B2 vaccine. No 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.   This case belongs to patient no 7 of 8 patients reported. Concomitant and 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.  Patient's symptoms included difficulty with mobility and balance. Patient reported pseudo-relapse symptoms after the mRNA-1273 booster which involved worsening balance lasting for 15 days. Patient also experienced a pseudo-relapse following the second BNT162b2 dose with similar symptoms.  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. There was no permanent neurological disability or severe, life-threatening adverse events reported. No treatment was recommended or performed during any of our pseudo-relapse cases. No acute cases of MS relapse were noted in our studied population that could be confirmed by clinical or radiological findings.   This case was linked to US-MODERNATX, INC.-MOD-2023-732774 (Linked 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 Co-suspect product that included non-company product BNT162B2 for COVID-19 prophylaxis, who experienced the serious unexpected medically significant multiple sclerosis pseudo relapse. The event occurred after receiving the (third) booster dose of mRNA-1273 vaccine (event and vaccine date were not provided). The patient received 2nd dose of the BNT162B2 vaccine. No 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