Headache after the third vaccination may be due to physiological reasons, because the body’s immune system has a relevant reaction, which is normal. It may also be due to pathological reasons, such as respiratory tract infection, high blood pressure, meningioma, etc., which is abnormal, and you need to go to the hospital in time to find out the reasons for treatment. 1. Physiological reasons: some uncomfortable symptoms may appear after vaccination, such as fever, dizziness, headache, and redness, swelling and pain at the vaccination site. This is mainly due to the body’s immune system reaction after vaccination, so that the patient to obtain the ability to resist the relevant viral and bacterial infections, this situation causes discomfort is normal. 2. Pathologic causes: (1) Respiratory tract infection: if the fever lasts for a long time, such as repeated fever for more than three days, especially the phenomenon of high fever with headache, it is very likely that a respiratory tract infection has occurred. (2) Hypertension: If the patient suffers from hypertension, and the blood pressure increases significantly after the new coronary vaccine is administered, it may cause the patient to have a headache after the first vaccination. (3) Meningioma: Patients with meningioma may develop headache due to increased intracranial pressure after receiving New Crown Vaccine. If physiological causes are excluded, it is recommended to visit the hospital in time for targeted treatment under the guidance of the doctor.