A headache after a vaccination may be a result of some mild adverse reactions. Most people may experience some uncomfortable symptoms after vaccination, such as fever, dizziness, headache, and painful redness and swelling at the vaccination site. This is mainly due to the related reaction of the body’s immune system after vaccination, thus allowing the patient to gain the ability to resist the related viral and bacterial infections. Usually, through proper rest, the pain can be gradually relieved after a few days and no special treatment is needed. However, it may also be a physiological headache caused by recent lack of sleep and exertion and excessive emotional stress during vaccination. Patients are advised to take more rest after vaccination, avoid straining, ensure sufficient sleep, pay attention to a reasonable diet, and do not eat raw, cold, or stimulating foods. In addition, if the patient himself has certain underlying diseases, such as hypertension, hyperlipidemia, cervical spondylosis, heart failure, cerebral ischemia, etc., the headache may also be caused by the lack of oxygen to the brain and insufficient blood supply to the brain due to the disease. In addition to headache, if the patient has serious conditions such as chest tightness and difficulty in breathing, it is recommended to go to the hospital for treatment. The symptoms of headache will also be relieved by actively treating the primary cause.