GUILLAIN BARRE SYNDROME; This spontaneous report received from a consumer concerned a 62 year old male. The patient's height, and weight were not reported. The patient's concurrent medical history included diabetes. The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin not reported, batch number: 1805025, and expiry: 25-MAY-2021) dose was not reported, administered on 12-MAR-2021 for prophylactic vaccination. Concomitant medications included insulin for diabetes. The patient was in Critical Care unit. On Saturday, the next day after the vaccine, the patient was not felling well in afternoon and had laid down for few hours. They had a trip scheduled for Sunday. The patient was feeling well when he left home on Sunday. By Friday, 19-MAR-2021 (a week from the day he got his vaccine), he started with leg and knee pain. On 20-MAR-2021, the pain moved up to his back and then into his shoulders. The patient arrived home on Friday, 19-MAR-2021 and at 9:30 pm that night the patient woke up and could not handle the severe pain. On 20-MAR-2021, the patient was admitted to emergency room to ensure it was not heart related. The patient had a spinal trap on Saturday and by Sunday/Monday the patient found out it was Guillain barre syndrome. The patient was not able to walk and had also lost feeling from the neck down and could not move. The reporter had stated, the patient's right side was worse then left so doctors had investigated occurrence of stroke but nothing was found. The patient had episodes where he was unable to speak but was feeling better. He could talk and communicate better, but was limited and could not write. The doctors were working on getting the patient strong enough for rehab. The patient wife had stated that the recovery expected to be a long process. The patient wife also stated that patient was not on ventilator.  The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient had not recovered from Guillain barre syndrome. This report was serious (Hospitalization Caused / Prolonged, Life Threatening, and Disability Or Permanent Damage).; Sender's Comments: V0: A 62-year-old white male experienced Guillain-Barre Syndrome (GBS) 8 or 9 days after vaccine. Medical history included diabetes, for which he took insulin. On day 7 after vaccine, he started with leg and knee pain. On day 8, the pain moved up to his back and then into his shoulders, that night the patient was troubled by worsening pain and presented to emergency room. The patient had a spinal tap that day and within 1-2 days the patient found out it was GBS. The patient was not able to walk and had also lost feeling from the neck down and could not move. The patient's right side was worse than left so doctors had investigated occurrence of stroke but nothing was found. The patient had episodes where he was unable to speak but was feeling better. He could talk and communicate better but was limited and could not write. The doctors were working on getting the patient strong enough for rehab. The patient was not on a ventilator and a long recovery was anticipated. No laboratory results were reported, including those of campylobacter, viral infections, or cerebrospinal fluid analysis. Although there is a close temporal relationship, there is insufficient information to make a meaningful medical assessment. Additional information has been requested, including consent to contact the treating physicians to obtain additional details of clinical care and diagnostics.