Dizziness after the third vaccination may be a normal reaction to the vaccine; it may also be caused by other reasons. 1. Normal vaccine reaction: after vaccination, fever, dizziness and other symptoms may occur, and may also cause redness, swelling and pain at the vaccination site, which will generally be relieved within three days without special treatment. 2. Other causes: If dizziness persists, further examination is needed to determine whether there is cervical spine disease, abnormal blood pressure, insufficient cerebral blood supply and other causes. It is necessary to check the causes of dizziness, and take appropriate treatment measures according to the causes. If the symptoms recover on their own within three days, no treatment is needed. If the symptoms are severe or persistent, you should go to the hospital as soon as possible.