The fourth dose of the New Crown vaccine has not yet been widely administered. Contraindications include acute exacerbation of chronic diseases, and precautions include observation of adverse reactions. At present, China has not yet launched the fourth vaccination of the new crown vaccine on a wide scale, and whether it is necessary to be vaccinated thereafter will be subject to official notification. Its contraindications and precautions are generally the same as the first three, contraindications mainly include acute attacks of chronic diseases, pregnancy, epilepsy and other uncontrolled mental illnesses, history of severe allergies and so on. Precautions mainly include meeting the conditions of vaccination, such as the third injection requires the completion of the first two injections and an interval of 6 months; after completion of the vaccination, you need to stay at the scene for 30 minutes; the emergence of serious adverse reactions, such as respiratory failure and other needs to consult a doctor in a timely manner, and so on. The details are subject to the guidance of the medical staff on site.