The third injection of the New Crown vaccine mainly serves as a booster, and there is usually no harm from the third injection of the New Crown vaccine in people without contraindications to vaccination. Adverse reactions such as localized pain, malaise, and low-grade fever may occur in some people. The third injection of the new crown vaccine may be a booster injection of inactivated vaccine or the third injection of recombinant subunit vaccine, and those who have no contraindications to vaccination should be actively vaccinated, which is of great significance in the prevention of infections, the reduction of the chances of the onset of disease turning into a serious illness, and the formation of a herd immunity barrier. Most people are not harmed by vaccination, and on the whole, the benefits outweigh the disadvantages. However, vaccine is a foreign substance to the organism, so some people may have adverse reactions after the third vaccination, such as redness, swelling and pain at the injection site, low-grade fever, dizziness, fatigue, muscle pain, etc., which will usually improve on their own after a few days. Very few people will have severe skin allergic reactions, or even breathing difficulties, shock and other symptoms. Therefore, vaccination must meet the vaccination requirements. People who are allergic to the vaccine, pregnant women, nursing mothers, people with high blood sugar, diabetes, malignant tumors, need to be cautious about vaccination. In addition, during the vaccination period, you need to ensure adequate sleep, light diet, avoid alcohol and spicy, stimulating and greasy food.