First we need to find out the nature of the first vaccine and then decide whether to revaccinate or not depending on the different nature of the vaccine. For adenovirus carrier vaccine, the second booster shot can be given directly; for inactivated vaccine and recombinant subunit vaccine, it is recommended to revaccinate the whole course of the vaccine.
At present, the main types of new coronavirus vaccines available in China include inactivated vaccines, adenovirus carrier vaccines and recombinant subunit vaccines.
In order to ensure the best immunization effect, the second dose of inactivated vaccine should be completed as early as possible within 8 weeks after the first dose; while adenovirus carrier vaccine requires only one dose for the whole course of the vaccine; it is recommended that the interval between the first and second doses of recombinant subunit vaccine should be at least 4 weeks, and the second dose should be completed as early as possible within 8 weeks after the first dose of inactivated vaccine.
In the case of adenovirus-vectored vaccine, a booster can be given directly after the first dose has been given for more than one year;
In case of inactivated vaccine and recombinant subunit vaccine, due to the time limit of 8 weeks between the first dose and the second dose, it is not recommended to receive the second dose directly if the interval is more than one year, and then it is recommended to re-vaccinate in order to ensure that the human body obtains the best protective effect after vaccination.