Possible autoimmune encephalitis; 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 ENCEPHALITIS AUTOIMMUNE (Possible autoimmune encephalitis) in a 75-year-old male patient who received mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.   LITERATURE REFERENCE:     Previously administered products included for COVID-19 prophylaxis: Pfizer (Dose 1), Pfizer (Dose 3) and Pfizer (Dose 2). Past adverse reactions to the above products included No adverse event with Pfizer, Pfizer and Pfizer. Concurrent medical conditions included Coronary artery disease, Hypertension and Diabetes.    On an unknown date, the patient received fourth dose of mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (unknown route) 1 dosage form. On an unknown date, the patient experienced ENCEPHALITIS AUTOIMMUNE (Possible autoimmune encephalitis) (seriousness criteria hospitalization and medically significant), INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and COVID-19 IMMUNISATION (Revaccination with different COVID-19 vaccine). The patient was hospitalized for 5 days due to ENCEPHALITIS AUTOIMMUNE. At the time of the report, ENCEPHALITIS AUTOIMMUNE (Possible autoimmune encephalitis) had resolved and INTERCHANGE OF VACCINE PRODUCTS (Interchange of vaccine products) and COVID-19 IMMUNISATION (Revaccination with different COVID-19 vaccine) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Angiogram: head and neck showed only periventricular hyperintensities with no diffusion restriction suggestive of chronic microvascular disease and mild cerebral atrophy. No meningeal enhancement. On an unknown date, Anti-NMDA antibody: were also nonreactive. On an unknown date, Anti-neuronal antibody: Negative, were also nonreactive, Negative and Negative. On an unknown date, Bacterial test: (Negative) Escherichia coli K1 was negative, Haemophilus influenzae. On an unknown date, Blood culture: were unyielding. On an unknown date, Blood glucose (40-70 mg/dl): 75 mg/dl. On an unknown date, Body temperature: afebrile. On an unknown date, CSF myelin basic protein (0-5.6 ng/mL): 29.6 ng/mL. On an unknown date, CSF oligoclonal band: were observed. On an unknown date, CSF test: Signs of aseptic inflammation. Showed lymphocytic pleocytosis with a slight elevation of protein.. On an unknown date, Computerised tomogram head: Acute stroke was ruled out. On an unknown date, Cryptococcus test: (Negative) cryptococcal was negative and Negative. On an unknown date, Cytomegalovirus test: Negative. On an unknown date, Drug screen: unremarkable. On an unknown date, Electroencephalogram: showed posterior dominant rhythm of mixed theta and delta waves with superimposed faster frontotemporal delta waves but with no epileptiform discharges or focal slowing. On an unknown date, Enterovirus test: Negative. On an unknown date, Epstein-Barr virus test: Negative. On an unknown date, Full blood count: unremarkable. On an unknown date, Herpes simplex test: (Negative) type 1 and 2. On an unknown date, Human herpes virus 6 serology: Negative. On an unknown date, Inflammatory marker test: not elevated. On an unknown date, Listeria test: Negative. On an unknown date, Lymphocyte percentage (40-80 %): 62 %. On an unknown date, Magnetic resonance imaging: head and neck showed only periventricular hyperintensities with no diffusion restriction suggestive of chronic microvascular disease and mild cerebral atrophy. No meningeal enhancement. On an unknown date, Metabolic function test: unremarkable. On an unknown date, Mycobacterium test: (Negative) Negative even after one week of incubation. On an unknown date, Neisseria test: Negative. On an unknown date, Physical examination: global aphasia and bilateral Babinski sign with no focal neurological sign., Physical exam findings during hospitalization showed gradual improvement over the five days course of hospitalization. and (Negative) Nuchal rigidity as well as other signs of meningeal irritation was also negative including Kerning's sign and Brudziniski's sign. On an unknown date, Protein total (12-60 mg/dl): 76 mg/dl. On an unknown date, Streptococcus test: Negative. On an unknown date, Treponema test: Negative. On an unknown date, Urine analysis: were unyielding. On an unknown date, Viral test: (Negative) varicella-zoster virus (VZV), and Parechovirus both was negative. On an unknown date, Vital signs measurement: stable. On an unknown date, West Nile virus test: was non-reactive. On an unknown date, White blood cell count (Unknown-<5 cells per millilitre): 9 cells per millilitre.     For mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (Unknown), the reporter considered ENCEPHALITIS AUTOIMMUNE (Possible autoimmune encephalitis) 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).    Concomitant and treatment medication were not reported. Patient was presented with several hours of history of altered mental status, aphasia, and behavioral changes. Patient received a booster dose of Moderna Bivalent mRNA COVID-19 vaccine one day prior to presentation. On the next day, patient had abrupt behavioral changes where he started to attempt eating a disposable plastic plate, having poor attention, urinating in a public place and abrupt onset of aphasia. No prior COVID-19 infection was reported  Nuchal rigidity as well as other signs of meningeal irritation was also negative including Kerning's sign and Brudziniski's sign. Two pairs of oligoclonal bands were observed in CSF and serum. Lyme serology was non-reactive. No evidence of infectious etiology was seen on the meningitis/encephalitis panel. Paraneoplastic panel was negative.  No active therapeutic measure was given, and the patient was watchfully monitored as signs of rapid improvement were appreciated. Aphasia resolved and no further behavioral changes were seen. At the end of hospitalization, he was neurologically intact and discharged home.   Author stated that the basis of our suggestion is the close temporal relationship between the onset of encephalitis and administration of the COVID-19 vaccine, abrupt onset of symptoms, relative rapid improvement without therapeutic intervention as well as lack of brain lesions on imaging.  Company Comment: This is a literature non-study case concerning a 75 year-old, male patient with a history of Coronary artery disease, Hypertension and Diabetes mellitus, who experienced the serious (due to medically important condition and hospitalization) unexpected, AESI of Encephalitis autoimmune, which occurred 1 day after the mRNA-1273.222 (Original/Omicron BA.4/5) vaccine, received as the fourth dose of COVID-19 vaccination schedule. Patient reported altered mental status, aphasia, and behavioral changes the day after vaccination. In the emergency department (ED), he was afebrile and his vital signs were stable. Physical exam showed global aphasia and bilateral Babinski sign with no focal neurological sign. Nuchal rigidity as well as other signs of meningeal irritation was also negative including Kerning's sign and Brudziniski's sign. Basic lab workup including complete blood count, comprehensive metabolic panel, and drug screen was also unremarkable. Acute stroke was ruled out by computed tomography (CT) head, CT angiography (CTA) head and neck, and also magnetic resonance imaging (MRI) that showed only chronic microvascular disease and mild cerebral atrophy. No meningeal enhancement was seen. Inflammatory markers were not elevated. Cerebrospinal fluid (CSF) analysis showed lymphocytic pleocytosis with a slight elevation of protein. The CSF was negative for cryptococcal, Epstein Barr virus (EBV), Cytomegalovirus (CMV), and venereal disease research lab (VDRL) test. The CSF acid-fast staining was negative even after one week of incubation. Meningitis/encephalitis panel including multiple virus and bacteria were also negative. A paraneoplastic panel including anti-Hu, anti-Yo, and anti-Ri antibodies was negative. Anti-NMDR and anti-Ma2 antibodies were also nonreactive. Two pairs of oligoclonal bands were observed in CSF and serum. Myelin basic protein was elevated at 29.6ng/mL (reference 0-5.6 ng/mL). Blood culture as well as urinalysis were negative. A 72-hour electroencephalogram (EEG) showed posterior dominant rhythm of mixed theta and delta waves with superimposed faster frontotemporal delta waves but with no epileptiform discharges or focal slowing. No active therapeutic measure was given, and the patient was watchfully monitored as signs of rapid improvement were appreciated. Physical exam findings during hospitalization showed gradual improvement over the five days course of hospitalization. Aphasia resolved and no further behavioral changes were seen. At the end of hospitalization, he was neurologically intact and discharged home. Additionally, Interchange of vaccine products and Revaccination with different COVID-19 vaccine (vaccination with three doses of COVID-19 vaccine Tozinameran) was noted in the case. The benefit-risk relationship of mRNA-1273.222 (Original/Omicron BA.4/5) vaccine is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 11-Nov-2022: Live Significant Follow up received by safety on 11-Nov-2022 has Email with FTA and Article propagated contains significant information: Reporter information, citation details, lab data, historical vaccine information, event and product information were updated.; Sender's Comments: Company Comment: This is a literature non-study case concerning a 75 year-old, male patient with a history of Coronary artery disease, Hypertension and Diabetes mellitus, who experienced the serious (due to medically important condition and hospitalization) unexpected, AESI of Encephalitis autoimmune, which occurred 1 day after the mRNA-1273.222 (Original/Omicron BA.4/5) vaccine, received as the fourth dose of COVID-19 vaccination schedule. Patient reported altered mental status, aphasia, and behavioral changes the day after vaccination. In the emergency department (ED), he was afebrile and his vital signs were stable. Physical exam showed global aphasia and bilateral Babinski sign with no focal neurological sign. Nuchal rigidity as well as other signs of meningeal irritation was also negative including Kerning's sign and Brudziniski's sign. Basic lab workup including complete blood count, comprehensive metabolic panel, and drug screen was also unremarkable. Acute stroke was ruled out by computed tomography (CT) head, CT angiography (CTA) head and neck, and also magnetic resonance imaging (MRI) that showed only chronic microvascular disease and mild cerebral atrophy. No meningeal enhancement was seen. Inflammatory markers were not elevated. Cerebrospinal fluid (CSF) analysis showed lymphocytic pleocytosis with a slight elevation of protein. The CSF was negative for cryptococcal, Epstein Barr virus (EBV), Cytomegalovirus (CMV), and venereal disease research lab (VDRL) test. The CSF acid-fast staining was negative even after one week of incubation. Meningitis/encephalitis panel including multiple virus and bacteria were also negative. A paraneoplastic panel including anti-Hu, anti-Yo, and anti-Ri antibodies was negative. Anti-NMDR and anti-Ma2 antibodies were also nonreactive. Two pairs of oligoclonal bands were observed in CSF and serum. Myelin basic protein was elevated at 29.6ng/mL (reference 0-5.6 ng/mL). Blood culture as well as urinalysis were negative. A 72-hour electroencephalogram (EEG) showed posterior dominant rhythm of mixed theta and delta waves with superimposed faster frontotemporal delta waves but with no epileptiform discharges or focal slowing. No active therapeutic measure was given, and the patient was watchfully monitored as signs of rapid improvement were appreciated. Physical exam findings during hospitalization showed gradual improvement over the five days course of hospitalization. Aphasia resolved and no further behavioral changes were seen. At the end of hospitalization, he was neurologically intact and discharged home. Additionally, Interchange of vaccine products and Revaccination with different COVID-19 vaccine (vaccination with three doses of COVID-19 vaccine Tozinameran) was noted in the case. The benefit-risk relationship of mRNA-1273.222 (Original/Omicron BA.4/5) vaccine is not affected by this report.