The live attenuated B brain vaccine can help prevent epidemic B encephalitis, but there may be pain, fever, rash, other and other reactions. 1. Pain: Pain may appear at the injection site within 24 hours after vaccination and will disappear within 2~3 days. 2. Fever: 1~2 weeks after vaccination, fever symptoms may occur, most of the performance of mild fever, usually lasts for 1~2 days will be relieved on their own, do not need special treatment, if moderate fever or fever for more than 48 hours, you can take the physical cooling or under the guidance of the doctor to take medication (such as ibuprofen, etc.) to deal with the method. 3. Rash: after vaccination, occasionally there are scattered skin rashes, usually do not need special treatment, if necessary, symptomatic treatment. 4. Other: rare adverse reactions, may be manifested as febrile convulsions, acute and rare adverse reactions manifested as allergic rash, anaphylactic shock, angioedema and so on. Contraindications, mainly including allergy to vaccine components and suffering from acute diseases, or severe chronic diseases, acute exacerbation of chronic diseases, patients with fever, pregnant women, as well as immunodeficiency, immunocompromised, or are receiving immunosuppressant therapy, suffering from encephalopathy and uncontrolled epilepsy, and other uncontrolled neurological diseases. It is recommended to go to a regular medical institution for vaccination, and seek medical attention in case of adverse reactions.