It is possible for a three year old child to develop a fever after receiving the Neocoronavirus vaccine. The New Crown vaccine is a biological agent that helps the organism to prevent infection by the New Crown virus, and the vaccination also reduces the rate of severe illness and mortality after one’s own infection with the New Crown virus. The Neocoronavirus vaccine is currently recommended for everyone three years of age and older, so three-year-olds can receive the Neocoronavirus vaccine when it is not contraindicated. Although the overall safety of the vaccine is relatively high, it cannot be ruled out that some vaccinees may experience fever as an adverse reaction after vaccination, which is usually mild and temporary. If a child develops a fever after vaccination, physical cooling is generally recommended, and if necessary, oral ibuprofen can be given to reduce the fever as prescribed by the doctor. However, if persistent high fever occurs, or if the fever is recurrent, prompt medical attention is recommended. Parents should pay attention to their children’s physical changes after vaccination and seek medical help if there is any serious adverse reaction.