On 11/07/2021 at 1523 client  date of birth 05/03/1999 (22-year old Male) was vaccinated in his Left Deltoid by RN for first-dose Johnson & Johnson (Lot#212A21A). At around 1529 as patient was seated following vaccination in the post-observation when staff MA called staff assistance/help. Charge RN and  2 post-observation RNs responded to the scene immediately around 1530 to find the patient lying on the ground. It was reported by post-observation RNs that patient had fell over from his chair and hit the Right anterior forehead.  RN reported that when she arrived on the scene she noticed the patients legs and right arm were shaking. Patient regained consciousness about 30 seconds after responding healthcare staff arrived to the scene. Patient was disoriented and RNs assessed that he had an area of redness to his Right anterior forehead. Patient stated he could not remember what happened just before he woke up on the floor. RNs assessed that patient was cold, clammy, and sweaty to touch. Patient was however able to verbalize to RNs his location, the date, the day of the week, and he remembered that he was at the vaccination site for his vaccine, A&Ox4. Patient denied any neck/back pain or discomfort. Patient sat up and denied any discomfort with movement, besides a headache. Patient was slowly assisted to wheelchair by RN staff, patient denied generalized discomfort but did exhibit generalized weakness upon ambulation. Initial HR at 1531 was 45 beats per minute (bpm), but improved by 1535 to HR 60 with a blood pressure (BP) of 115/51. Respirations and pulse oximetry remained within defined limits. By 1539 patient BP was 108/71 with HR 64 bpm.  Patient reported to RN staff that he had smoked marijuana at 1300 before coming in for his vaccination and had not eaten much food. Patient stated he felt better after drinking some apple juice. RN staff were about to call 911 but patient verbally declined that staff call for help. Patient was strongly encouraged by responding RN staff to go to the emergency room even though he declined. Patient stated ?I will be okay?. Patient declined further. Patient educated about risks of declining emergency assistance and informed by RN staff that if he had any changes in his current mental status such as exhibiting drowsiness, disorientation, or increased headache pain to call for emergency assistance immediately. Patient and patient?s wife verbalized understanding. Patient family informed to not let the patient go to sleep Patient stated he was feeling well. Patient wife was present during the event. Patient?s wife?s cousin who was also vaccinated would per the family be driving the patient home. Before leaving patient was moved in wheelchair by RN staff to lie down for 30 minutes on the secluded patient area on a medical cot. Patient was given a neuro assessment before leaving facility: patient bilateral hand grips strong, patient able to pull with both arms strongly, patient verbalized sensation to upper and lower extremities, patient extraocular movements within defined limits, patient face symmetrical, and patient states headache improved. Patient vital signs re-checked and stable. Patient dangled feet off medical cot and slowly stood, patient denied dizziness or weakness upon ambulation. Patient again refused emergency assistance but he and his wife stated they would call related to previous education given to them by RNs. Patient ambulated out of the clinic with wife without issue with a stable gait.