Headache after vaccination may be caused by adverse reaction of vaccine, cold after vaccination, high blood pressure attack and so on. 1. Adverse reaction of vaccine: after vaccination, the body’s immune system will have relevant reactions. Some patients may have adverse reactions such as headache, fever, redness, swelling and pain at the vaccination site. 2. Cold after vaccination: after vaccination, cold, due to the growth and reproduction of pathogenic microorganisms can produce toxins, which will cause stimulation of local blood vessels in the head, resulting in spasm of blood vessels, which can cause microcirculation disorders, and then can lead to contracture of the head muscles, which can cause headache. 3. Hypertension attack: when hypertension attack, due to the elevation of blood pressure can cause intracranial pressure rise, can lead to cerebral vascular spasm, which can cause headache. After vaccination headache, need to actively consult a professional doctor, if the symptoms are more obvious, need to go to the hospital in time for examination and treatment, to avoid delaying the condition.