In the case of the new coronavirus vaccine, for example, the third dose of the three-dose vaccine can be administered within six months of the first dose, and if the third dose is a booster, it should be administered at least six months apart. If the vaccine is a recombinant subunit vaccine, generally three doses are needed to form a complete immunization program, and the third dose should be given within six months of the first dose. If the vaccinee receives two doses of vaccine, mostly inactivated vaccine, the purpose of the third injection is to strengthen the immune ability of the human body that decreases over time, and then the vaccination can be delayed for about six months at the latest. If the vaccination is delayed due to allergy or other adverse reactions after vaccination, the vaccinee should reflect the situation to the doctor in time and ask for the vaccination schedule. Vaccinees should receive the third vaccination in a timely manner according to their own situation, and consult a doctor immediately if they have any problems.