Myasthenia gravis; COVID-19; Primary Sjogren's Syndrome; This literature-non-study case was reported in a literature article and describes the occurrence of MYASTHENIA GRAVIS (Myasthenia gravis), COVID-19 (COVID-19) and SJOGREN'S SYNDROME (Primary Sjogren's Syndrome) in a 67-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 prophylaxis.       No Medical History information was reported.   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 MYASTHENIA GRAVIS (Myasthenia gravis) (seriousness criterion hospitalization), COVID-19 (COVID-19) (seriousness criterion hospitalization) and SJOGREN'S SYNDROME (Primary Sjogren's Syndrome) (seriousness criteria hospitalization and medically significant). The patient was treated with PYRIDOSTIGMINE at an unspecified dose and frequency; IMMUNOGLOBULINS NOS (IMMUNOGLOBULIN I.V) (intravenous) at an unspecified dose and frequency and PREDNISONE at an unspecified dose and frequency. At the time of the report, MYASTHENIA GRAVIS (Myasthenia gravis) and COVID-19 (COVID-19) was resolving and SJOGREN'S SYNDROME (Primary Sjogren's Syndrome) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Antiacetylcholine receptor antibody: Antibodies against Acetylcholine receptors were elevated. On an unknown date, Antibody test: (Positive) Positive for primary sjogren's syndrome antibodies and On the fifth day, PSS antibodies were also detected. On an unknown date, Chest X-ray: Unremarkable. On an unknown date, Computerised tomogram head: Unremarkable. On an unknown date, Computerised tomogram thorax: Unremarkable. On an unknown date, HIV antibody: within the normal range. On an unknown date, Laboratory test: Lyme test was within the normal range. On an unknown date, Physical examination: Remarkable for bilateral ptosis and difficulty ambulating. On an unknown date, SARS-CoV-2 test: (Positive) Positive. On an unknown date, Thyroid function test: Thyroid was within the normal range. On an unknown date, Treponema test: RPR test was within the normal range. On an unknown date, Vitamin B12: within the normal range.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered MYASTHENIA GRAVIS (Myasthenia gravis) and COVID-19 (COVID-19) to be related. No further causality assessment was provided for SJOGREN'S SYNDROME (Primary Sjogren's Syndrome).    No concomitant medication was reported.  The patient presented with complaints of progressive weakness for 2 weeks, which began as diffuse malaise, and progressed to upper and lower extremity weakness with associated neck weakness, and dysphagia.  The patient was admitted to the ICU for suspected new onset neuromuscular junction disorder and for close monitoring of respiratory function. The patient was started on Pyridostigmine and IVIG, with low dose prednisone initiated on day 3 of admission. On the fifth day, symptoms improved significantly. The diagnosis of Myasthenia Gravis was made. Author stated that as the patient received the COVID-19 vaccine, it was considered an autoimmune reaction secondary to his administration. CC:This is a literature non-study case concerning a 67-year-old male patient with no reported medical history, who experienced the unexpected, serious (hospitalization) adverse event of special interest of Myasthenia gravis and the unexpected, serious (hospitalization) events of COVID-19 and Sjogren's syndrome, 2 weeks after receiving the third dose of mRNA-1273 vaccine. The patient was present with diffuse malaise and progressed to upper and lower extremity weakness with associated neck weakness and dysphagia. The patient was admitted to the ICU for suspected new-onset neuromuscular junction disorder and for close monitoring of his respiratory function. COVID-19 PCR was positive and imaging studies were unremarkable. The patient was started on Pyridostigmine and IVIG with low dose prednisone initiated on day 3 of admission and symptoms improved significantly 2 days later. Antibodies (Ab) against Acetylcholine (Ach) receptors were elevated and was diagnosed with Myasthenia gravis. Primary Sjogren's Syndrome (PSS) antibodies were also detected. Other diagnostic test results of the diseases that may mimic neuromuscular junction dysfunction were within normal range. The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: This is a literature non-study case concerning a 67-year-old male patient with no reported medical history, who experienced the unexpected, serious (hospitalization) adverse event of special interest of Myasthenia gravis and the unexpected, serious (hospitalization) events of COVID-19 and Sjogren's syndrome, 2 weeks after receiving the third dose of mRNA-1273 vaccine. The patient was present with diffuse malaise and progressed to upper and lower extremity weakness with associated neck weakness and dysphagia. The patient was admitted to the ICU for suspected new-onset neuromuscular junction disorder and for close monitoring of his respiratory function. COVID-19 PCR was positive and imaging studies were unremarkable. The patient was started on Pyridostigmine and IVIG with low dose prednisone initiated on day 3 of admission and symptoms improved significantly 2 days later. Antibodies (Ab) against Acetylcholine (Ach) receptors were elevated and was diagnosed with Myasthenia gravis. Primary Sjogren's Syndrome (PSS) antibodies were also detected. Other diagnostic test results of the diseases that may mimic neuromuscular junction dysfunction were within normal range. The benefit-risk relationship of mRNA-1273 is not affected by this report.