LEFT SIDE BRAIN STROKE (ON THE FRONT SIDE OF BRAIN); HEADACHE (WORSE); This spontaneous report received from a patient concerned a 50 year old female. The patient's height, and weight were not reported. The patient's past medical history included: former cigarette smoker (stopped smoking after the stroke), and concurrent conditions included: pancreatitis, iodine allergy, colitis, non alcohol user, and non smoker, and other pre-existing medical conditions included: Patient not have any drug abuse or illicit drug usage. Patient did not used her medication before 2 weeks of vaccination. The patient was previously treated with atropine sulfate/diphenoxylate hydrochloride, and promethazine.  The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin not reported, batch number: 1808980, expiry: 18-SEP-2021) dose was not reported, 1 total, administered on 06-APR-2021 to right arm for prophylactic vaccination. No concomitant medications were reported.  On 10-APR-2021, the patient experienced back to back headaches. Patient told to her husband that she was experiencing headache but both brushed it off. Patient noted on TV that ,headache was one of the side effect after vaccination. On 14-MAY-2021, 38 days after the vaccination, patient woke up with drooping right side of face and was not able to answer the phone when it was ringing. Patient was looked in the mirror and saw that her right eye and mouth were drooping on right side. Patient reported that, she experienced the left sided brain stroke while she was asleep and that was affecting the right side of her face and speech. On 14-MAY-2021, patient was admitted to the hospital. On 14-MAY-2021, Blood work, Ultrasound Scan, X-Ray, Carotid Artery Ultrasound in neck and Magnetic Resonance Imaging (MRI) were performed on patient to confirm the stroke. It was confirmed that patient had left sided brain stroke (on the front left side of her brain). On 17-MAY-2021, patient was discharged from hospital. Patient reported that, she still had headache and ongoing difficulty with speech, when nervous or too excited starts to stutter. On 23-AUG-2021, patient was seen by her Primary Care Provider (PCP) to follow up on recent episode where patient was unable to recognize where she was on Monday or Tuesday of last week. The patient nurse practitioner referred patient for another Magnetic Resonance Imaging (MRI) because of patient headache seems to be getting worse. Patient reported that, she did not want another shot due to her experience with the vaccine and fears another vaccine might do her more harm rather than good. Patient was hospitalized for 4 days. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient had not recovered from left side brain stroke (on the front side of brain) and headache (worse). This report was serious (Hospitalization Caused / Prolonged).; Sender's Comments: V0:20210851762- covid-19 vaccine ad26.cov2.s - Left side brain stroke (on the front side of brain). This event(s) is considered unassessable. The event(s) has a compatible/suggestive temporal relationship, is unlabeled, and has unknown scientific plausibility. There is no information on any other factors potentially associated with the event(s). 20210851762- covid-19 vaccine ad26.cov2.s - Headache (worse). This event(s) is labeled per RSI and is therefore considered potentially related.