Whether the third shot is needed or not depends on whether it is a two-dose or three-dose vaccine. If it is the New Crown inactivated vaccine, it is recommended that the third dose be given in a timely manner. 1. Two-dose vaccine: After two doses of two-dose vaccine have been administered, all procedures of the vaccine have been completed, and the immune system has started to generate antibodies, the third shot at this time is a kind of booster shot, which can be chosen according to your own wishes and needs, and is not mandatory at present. 2. Three-dose vaccine: three-dose vaccine must be the third shot, because only two shots can not play a sufficient antibody protection effectiveness, as long as there is no serious allergic reaction during the vaccination process, while there is no relevant contraindication, should be in accordance with the prescribed time to play the third shot, in order to play a better protective effect. It is recommended that the vaccinated person should first clarify his/her vaccine type, and then strictly follow the doctor’s instructions to determine whether he/she should take the third vaccine.