MENTAL DECLINE; COGNITIVE IMPAIRMENT; CHRONIC INFLAMMATORY DEMYELINATING POLYNEUROPATHY; EQUINE SYNDROME; CONSIDERABLE WEIGHT LOSS; VISION DISTURBANCES; DIARRHEA ON AND OFF; This spontaneous report received from a consumer concerned a 76 year old female. The patient's weight was 159 pounds, and height was not reported.  The patient's concurrent conditions included eggs yolk allergy, shellfish allergy (nausea/vomiting), irritable bowel syndrome, essential hypertension, hypomagnesemia, dysphagia, severe protein calorie malnutrition, muscle weakness, and hypothyroid. The patient was not pregnant at the report time. The patient experienced rash when treated with liothyronine sodium, and sertraline, and paralysis when treated with suxamethonium, and hives when treated with penicillin NOS (not otherwise specified), sulfadiazine, and passed out when treated with codeine.  The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin not reported, batch number: 1016022, expiry: UNKNOWN) dose was not reported, 1 total, administered on 06-MAY-2021 for prophylactic vaccination. Concomitant medications included alendronate sodium for drug used for unknown indication, amlodipine for drug used for unknown indication, amlodipine besilate for drug used for unknown indication, bupropion for drug used for unknown indication, buspirone for drug used for unknown indication, buspirone hydrochloride for drug used for unknown indication, celecoxib for drug used for unknown indication, citalopram hydrobromide for drug used for unknown indication, dicycloverine for drug used for unknown indication, dicycloverine hydrochloride for drug used for unknown indication, ergocalciferol for drug used for unknown indication, levothyroxine for drug used for unknown indication, levothyroxine sodium for drug used for unknown indication, naloxone for drug used for unknown indication, ondansetron for drug used for unknown indication, pantoprazole sodium sesquihydrate for drug used for unknown indication, paracetamol for drug used for unknown indication, prochlorperazine for drug used for unknown indication, propranolol for drug used for unknown indication, bupropion hydrochloride, citalopram, colecalciferol, diphenhydramine, docusate/senna alexandrina, heparin, loperamide hydrochloride, macrogol, magnesium oxide, pantoprazole, prednisone, salbutamol, sodium chloride, loperidine and tramadol.  The patient's diarrhea started on 08-MAY-2021 and was on and off for several days. The patient had vision disturbance started around 13-MAY-2021 or 14-MAY-2021. The eyes could not focus, and patient could not use cell phone due to vision disturbance. The patient's other problems started around 14-MAY-2021. The patient had been having nerve issues complications (Equine Syndrome). The patient was able to use upper body fine, but lower body had difficulty to mobilize. The patient was moved into a nursing facility and then had issues after that. The patient was having issues swallowing, tremors in face, problems with hands shaking and her fingers were almost bent in a weird position. On 19-MAY-2021, the patient was sent to emergency room (ER). The patient got infusion treatments of IVIG (intravenous immunoglobulin) and other steroids. The issues progressed to the point that she could not use her hands. The patient was in hospital for 6 days. The patient was progressively getting worse and had challenges of choosing correct words when talking to daughter. The rehab facility then sent her back to ER, where she was admitted ever since. The patient could not have foods that were not pureed. The diagnosis was chronic inflammatory demyelinating polyneuropathy and cognitive impairment. On 25-MAY-2021, the patient experienced mental decline. The goal was to give IVIG and prednisone infusions monthly, but unsure if it would help her. As on report time, the patient could use hands and swallow better again. The patient's mental/cognitive decline had been very recent and had not resolved. The patient's daughter had been unsuccessful to get hospital to give her a computerized tomogram scan again. Since MAR-2021, the patient had gone from 220 pounds to 159 pounds now (considerable weight loss). On 20-MAY-2021, the patient was 186 pounds. The rehab facility was giving doses of gabapentin 400 mg thrice daily. When patient refused to take it, they refused to help her, so she started taking it again. The patient was no longer on gabapentin.  The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient recovered from vision disturbances on 17-MAY-2021, and diarrhea on and off on an unspecified date, was recovering from chronic inflammatory demyelinating polyneuropathy, and equine syndrome, had not recovered from cognitive impairment, and mental decline, and the outcome of considerable weight loss was not reported. This report was serious (Hospitalization Caused / Prolonged).; Sender's Comments: V0:  This spontaneous report received from a consumer concerns a 76-year-old white female who was diagnosed with chronic inflammatory demyelinating polyneuropathy and cognitive impairment; with symptoms of "vision disturbance", "nerve issue complications" with lower body difficult mobility, issues swallowing, tremors in face, problems with hands shaking and her fingers were almost bent in a weird position approximately 8 days after receiving Janssen Covid-19 vaccine.  Concurrent illness includes irritable bowel syndrome, essential hypertension, hypomagnesemia, dysphagia, severe protein calorie malnutrition, muscle weakness, and hypothyroidism.  The patient complained of diarrhea 2 days after vaccination.  On 13th post-vaccination day (PVD), the patient was brought to the emergency room, IVIG and unspecified steroids were given; the patient was subsequently hospitalized for 6 days.  On 19th PVD, the patient presented with "mental decline; and >25kg weight loss in 2 months prior to hospitalization was reported.  The patient recovered from vision disturbances and diarrhea; recovering chronic inflammatory demyelinating polyneuropathy, and equine syndrome; not recovered from cognitive impairment, and mental decline; the outcome of outcome of considerable weight loss was not reported.  No other details reported.  Based on the diagnosis of chronic inflammatory demyelinating polyneuropathy, the latency of 8 days from the vaccination does not suggest a plausible explanation.  There is an increased risk of cuada equina in the elderly due to vertebral canal stenosis.  The advanced age also increases the risk for mental decline and cognitive impairment.  However, a relationship with Janssen Covid-19 vaccine cannot be ruled out and thus the relationship is considered indeterminate.